Kamltech

Profibus Cable, Connector And Termination Tips

2020-01-08T11:12:00.001+05:30

PROFIBUS (Process Field Bus) is a standard for fieldbus communication in automation technology and was first promoted in 1989 by BMBF (German department of education and research) and then used by Siemens. It should not be confused with the PROFINET standard for Industrial Ethernet. PROFIBUS is openly published as part of IEC 61158.

Profibus comes in four variants, each with a different purpose:

PROFIBUS DP (Decentralized Peripherals) used to drive sensors and actuators via a central controller. Dataspeed up to 12 Mbit/s with twisted pair cables and fiber optic cables are an option.
PROFIBUS PA (Process Automation) is used to monitor measuring equipment via a process control system. This Profibus variant is ideal for use in explosive areas (Ex-zone 0 and 1). In the cables flows namely a weak current through the bus lines in an intrinsically safe circuit so that sparks do not occur, even at fault. The con. about this variant is the slow dataspeed at 31,25 kbit/s.
PROFIsafe used for safety applications, usually with safety PLC’s or safety relays.
PROFIdrive used in motion control.

Profibus Cable

Profibus Connector:

Pin #	Function	Description
1	Shield	Shield and functional earth
2	NC	Not in use
3	RxD/TxD-P	Data recieve and transmit (positive)
4	CNTR-P	Control signal to repeater (positive)
5	DGND	Reference potential for +5 volt and data
6	VP	+5 volt for terminating resistors (active termination)
7	NC	Not in use
8	RxD/TxD-N	Data recieve and transmit (negative)
9	CNTR-N	Control signal to repeater (negative)

Profibus Wire Cutter:

The first thing to do is to remove the isolation of your Profibus cable. You can use a special Profibus Tripping Tool or if you are used to work with cables, you can use a knife or a wire cutter. The Profibus stripping tool is worth the money, because it will give you a sharp and perfect stripping of the Profibus cable needed for the connectors. It can be difficult to strip the cables correctly with a knife, so that both the shield and the two wires inside are visible.

How to Connect the master & slave ?

One master and slave connector as below diagram, The master connection in use a incoming entry only with switch on condition & slave connection for fist slave also incoming connection with the switch off condition. If other slave are connector then slave outgoing cable connected the next connector with on the terminal switch & other slave off.

Connecting the Profibus cable to the connector should be done with extra caution. Remember, that it is very important not only to connect the wires correct, but also to connect the shield correct and even to strip the wire correct. Take a look at this great instruction video if you’re in doubt about the connector:

Allen Bradley's Hardware & Software

2019-12-08T19:07:00.002+05:30

Allen Bradley's / Rockwell Automation:

Allen-Bradley is the brand-name of a line of factory automation equipment, today owned by Rockwell Automation.

PLC Harware:

Micrologic-1000,1200,1400,1500

Micrologix 1200

Below are the graphical representation of the all the module for different PLC hardware.

Micrologix1000

SLC5/01, 5/02, 5/03,5/04,5/05:

SLC PLC

Programming Software:

RSLogix500 is the programming software to create the ladder logic programming for PLC.
This software work in above PLC hardware.

Communication Software:

RSLinx software below are the display the version as well as the following icon generated in the screen.

Software installation

Logo for screen

Locating And Downloading Your Free Software!

You would think this step would be somewhat easy, however, if you’ve ever visited the Rockwell Automation website

Download the Free Rockwell Software we need, Do the following:

Go to Product Compatibility and Download Center
At the top of the screen search for MicroLogix 1100 then Select firmware 10.000.
From selection choose Select Files option: Select RSLogix Micro Starter Lite w/o RSLinx EN

PLC Connection

2019-12-03T20:35:00.000+05:30

PLC having two type of connection: Sink Type/ Sources Type:

Sink Type Connection:

Sink Type Connection

The above connection check the all the output devices on end connected to the power supply +Ve site and PLC common connected to the -Ve/ 0Vdc supply.

Source Type:

Source Type Connection

The output device on terminal connected to the -Ve site of power supply and power supply +Ve side connected to the common of PLC card.

In Both the above connection scheme you see that both the connection are only difference the common point connection.

PLC also required the sensor type same as above ans connection as below:

Sensor type for NPN & PNP

Most of the time PLC used as a PNP type of sensor because the output generated in +Ve supply.

PLC Inside

2019-12-03T20:08:00.000+05:30

The PLC Inside

The PLC mainly consists of
1. CPU,
2. Memory areas,
3. Input Cards (Analog / Digital)
4. Output Cards(Analog/Digital)

We can actually consider the PLC to be a box full of hundreds or thousands of separate relays, counters, timers and data storage locations. Do these counters, timers, etc. really exist? No, they don't "physically" exist but rather they are simulated and can be considered software counters, timers, etc. These internal relays are simulated through bit locations in registers. (more on that later)

What does each part do?

INPUT RELAYS-(contacts)These are connected to the outside world. They physically exist and receive signals from switches, sensors, etc. Typically they are not relays but rather they are transistors.
INTERNAL UTILITY RELAYS-(contacts) These do not receive signals from the outside world nor do they physically exist. They are simulated relays and are what enables a PLC to eliminate external relays. There are also some special relays that are dedicated to performing only one task. Some are always on while some are always off. Some are on only once during power-on and are typically used for initializing data that was stored.
COUNTERS-These again do not physically exist. They are simulated counters and they can be programmed to count pulses. Typically these counters can count up, down or both up and down. Since they are simulated they are limited in their counting speed. Some manufacturers also include high-speed counters that are hardware based. We can think of these as physically existing. Most times these counters can count up, down or up and down.
TIMERS-These also do not physically exist. They come in many varieties and increments. The most common type is an on-delay type. Others include off-delay and both retentive and non-retentive types. Increments vary from 1ms through 1s.
OUTPUT RELAYS-(coils)These are connected to the outside world. They physically exist and send on/off signals to solenoids, lights, etc. They can be transistors, relays, or triacs depending upon the model chosen.
DATA STORAGE-Typically there are registers assigned to simply store data. They are usually used as temporary storage for math or data manipulation. They can also typically be used to store data when power is removed from the PLC. Upon power-up they will still have the same contents as before power was removed. Very convenient and necessary!!

What Is PLC?

2019-12-03T20:01:00.002+05:30

What is a PLC?

A PLC (i.e. Programmable Logic Controller) is a device that was invented to replace the necessary sequential relay circuits for machine control. The PLC works by looking at its inputs and depending upon their state, turning on/off its outputs. The user enters a program, usually via software, that gives the desired results.
PLCs are used in many "real world" applications. If there is industry present, chances are good that there is a plc present. If you are involved in machining, packaging, material handling, automated assembly or countless other industries you are probably already using them. If you are not, you are wasting money and time. Almost any application that needs some type of electrical control has a need for a plc.
For example, let's assume that when a switch turns on we want to turn a solenoid on for 5 seconds and then turn it off regardless of how long the switch is on for. We can do this with a simple external timer. But what if the process included 10 switches and solenoids? We would need 10 external timers. What if the process also needed to count how many times the switches individually turned on? We need a lot of external counters.
As you can see the bigger the process the more of a need we have for a PLC. We can simply program the PLC to count its inputs and turn the solenoids on for the specified time.
This site gives you enough information to be able to write programs far more complicated than the simple one above. We will take a look at what is considered to be the "top 20" plc instructions. It can be safely estimated that with a firm understanding of these instructions one can solve more than 80% of the applications in existence

PLC History

In the late 1960's PLCs were first introduced. The primary reason for designing such a device was eliminating the large cost involved in replacing the complicated relay based machine control systems. Bedford Associates (Bedford, MA) proposed something called a Modular Digital Controller (MODICON) to a major US car manufacturer. Other companies at the time proposed computer based schemes, one of which was based upon the PDP-8. The MODICON 084 brought the world's first PLC into commercial production.
When production requirements changed so did the control system. This becomes very expensive when the change is frequent. Since relays are mechanical devices they also have a limited lifetime which required strict adhesion to maintenance schedules. Troubleshooting was also quite tedious when so many relays are involved. Now picture a machine control panel that included many, possibly hundreds or thousands, of individual relays. The size could be mind boggling. How about the complicated initial wiring of so many individual devices! These relays would be individually wired together in a manner that would yield the desired outcome. Were there problems? You bet!
These "new controllers" also had to be easily programmed by maintenance and plant engineers. The lifetime had to be long and programming changes easily performed. They also had to survive the harsh industrial environment. That's a lot to ask! The answers were to use a programming technique most people were already familiar with and replace mechanical parts with solid-state ones.
In the mid70's the dominant PLC technologies were sequencer state-machines and the bit-slice based CPU. The AMD 2901 and 2903 were quite popular in Modicon and A-B PLCs. Conventional microprocessors lacked the power to quickly solve PLC logic in all but the smallest PLCs. As conventional microprocessors evolved, larger and larger PLCs were being based upon them. However, even today some are still based upon the 2903.(ref A-B's PLC-3) Modicon has yet to build a faster PLC than their 984A/B/X which was based upon the 2901.
Communications abilities began to appear in approximately 1973. The first such system was Modicon's Modbus. The PLC could now talk to other PLCs and they could be far away from the actual machine they were controlling. They could also now be used to send and receive varying voltages to allow them to enter the analog world. Unfortunately, the lack of standardization coupled with continually changing technology has made PLC communications a nightmare of incompatible protocols and physical networks. Still, it was a great decade for the PLC!
The 80's saw an attempt to standardize communications with General Motor's manufacturing automation protocol(MAP). It was also a time for reducing the size of the PLC and making them software programmable through symbolic programming on personal computers instead of dedicated programming terminals or handheld programmers. Today the world's smallest PLC is about the size of a single control relay!

The 90's have seen a gradual reduction in the introduction of new protocols, and the modernization of the physical layers of some of the more popular protocols that survived the 1980's. The latest standard (IEC 1131-3) has tried to merge plc programming languages under one international standard. We now have PLCs that are programmable in function block diagrams, instruction lists, C and structured text all at the same time! PC's are also being used to replace PLCs in some applications. The original company who commissioned the MODICON 084 has actually switched to a PC based control system.

Siemens PLC Feature Can Be Exploited for Evil - and for Good

2019-12-02T14:59:00.000+05:30

A hidden feature in some newer models of the vendor's programmable logic controllers leaves the devices open to attack. Siemens says it plans to fix it.

An undocumented access feature in some newer models of Siemens programmable logic controllers (PLCs) can be used as both a weapon by attackers as well as a forensic tool for defenders, researchers have discovered.

Researchers at Ruhr University Bochum in Germany stumbled across the hardware-based special access feature in Siemens' S7-1200 PLCs while studying its bootloader, which, among other things, handles software updates and verifies the integrity of the PLC's firmware when the device starts up.

They found that an attacker using the special access feature could bypass the bootloader's firmware integrity check within a half-second window when the PLC starts up and load malicious code to wrest control of the PLC's processes.

Just why the special access feature resides in the PLCs remains a mystery. There have been cases of embedded devices found harboring hidden maintenance ports left behind by vendors, for example, but the researchers were baffled by the existence of this one in the Siemens PLCs.

"We don't know why [Siemens has] this functionality," says Ali Abbasi, a research scholar at Ruhr-University Bochum, who, along with PhD student Tobias Scharnowski and professor Thorsten Holz, worked on the research. "Security-wise, it's wrong to have such a thing because you can also read and write to memory and dump the content of memory from the RAM."

The researchers shared their findings with Siemens, which says it's working on a fix for the vulnerability.

"Siemens is aware of the research from Ruhr University Bochum concerning hardware-based special access in SIMATIC S7-1200 CPUs. Siemens experts are working on a solution to resolve the issue. Siemens plans to publish further information regarding the vulnerability with a security advisory," the company said in a statement provided to Dark Reading. "Customers will be informed using the usual Siemens ProductCERT communication channels."

A key question is whether the fix requires a hardware replacement rather than a software update. When asked whether the PLC fix would be a software or hardware update, Siemens said its "experts are evaluating the alternatives."

But it turns out there is a silver lining with the Siemens PLC special access feature: "It's also useful for people like us who protect these devices. It provides for memory forensics of the PLC," Abbasi says.

The researchers were able to use the special access feature to view the content of the PLC memory, which means a plant operator could spot malicious code that may have been planted on his or her device. "Siemens doesn't let you see the content of the [PLC] memory, but you can do that with this special access feature," Abbasi says.

The researchers built a tool that performs this forensic memory dump, which they will release at Black Hat Europe next month in London when they will present their research findings

What They DidThe researchers were able to write their own code to the PLC's flash chip via its firmware update feature without the bootloader's checksum feature detecting it. The question, they say, is how to mitigate this type of attack since malicious code would be embedded into the flash memory of the bootloader.

"It really depends if Siemens can fix it via a software update or not. If they can with software, it also means the attacker can override the contents of the bootloader, which means there's no way to fix it," Abbasi says.

That's one reason the researchers wanted to release their tool for dumping contents of the firmware. "That then means an attacker can't hide his existence" in the PLC, Abbasi says.

An attacker with physical access to the port, or by rigging the PLC while it's being manufactured in the supply chain, could use this technique to read and write to the memory of the hardware. That would allow him or her to manipulate the operation of the PLC, providing phony measurements or other instrumentation data, for example.

"One of the main issues is there's this notion of trust in a newly delivered PLC," Scharnowski says.

He notes that it's not the special access feature itself that allows you to read and write to the flash. "It's a combination of features that if you put them together in a clever way, you can use them to get your own code execution on it," Scharnowski says. "If you can do that, then you can control the PLC fully."

Props for Siemens SecurityThe researchers say they chose to study Siemens' PLCs because it's one of the market leaders and also because there's little known publicly about the PLC's operating system, Adonis.

While many embedded systems today remain poorly secured, they say Siemens has done more with security than some other vendors.

"Honestly, if you compare them to other PLCs, they are doing very well. They keep adding features and security features that we have to bypass," Abbasi says. "They are doing a lot of good things that place them ahead of others in the embedded security domain."

Even so, the researchers maintain there's a lot more work to do in protecting plant operators from attackers or supply chain corruption of their PLCs. If there's a special feature like the one in Siemens PLCs, they say, the vendor should inform their customers. "Customers deserve to know so in their risk calculation they can consider this risk as well," Abbasi says.

The Ruhr University Bochum team's work is the latest in a string of PLC research projects. This summer another team of security researchers built a phony engineering workstation that was able to dupe and alter operations of the Siemens S7 programmable logic controller (PLC) after discovering that modern S7 PLC families running the same firmware also share the same public cryptographic key.

And in 2016, Abbasi, then a Ph.D. candidate at University of Twente, Netherlands, and Majid Hashemi, a system programmer and independent security researcher at the time of their research, created a PLC rootkit that could operate on any brand of PLC.

The Rise of Industrial IoT

2019-12-01T19:50:00.002+05:30

Special feature

The Rise of Industrial IoT

Infrastructure around the world is being linked together via sensors, machine learning and analytics. We examine the rise of the digital twin, the new leaders in industrial IoT (IIoT) and case studies that highlight the lessons learned from production IIoT deployments.

Fortinet and Siemens unveiled a partnership designed to better secure operational technology networks in markets such as utilities, transportation and oil and gas.

The announcement comes as Fortinet holds an analyst meeting in New York on Monday. The investor meeting is Fortinet's first in its decade as a public company. Fortinet competes with Palo Alto Networks, Checkpoint, and Cisco among others.

Under the alliance, Siemens will integrate its industrial and operational technologies and control systems with Fortinet's cybersecurity platform and Fortinet Security Fabric. The aim is to better secure edge computing and Internet of Things devices. The two companies also entered a global resell agreement.

Fortinet's security fabric.

Special feature

Cyberwar and the Future of Cybersecurity

Today's security threats have expanded in scope and seriousness. There can now be millions -- or even billions -- of dollars at risk when information security isn't handled properly.

The first effort from Fortinet and Siemens will be the integration of the FortiGate Next-Generation Firewall with the Ruggedcom Multi-Service Platform family of switches and routers. The Siemens gear is typically used in industrial settings such as electrical substations. Siemens will also bundle Fortinet's FortiGate Next-Generation firewall with its equipment.

Fortinet Chief Marketing Officer John Maddison said in an interview that edge computing and IoT are increasingly critical growth markets for Fortinet now and in the future. "Edge computing will need low latency compute and be built out in factories and other industrial areas. Coupled with 5G there will be a need for a new security model," said Maddison.

For now, Fortinet is growing at a rapid clip courtesy of its SD-WAN security portfolio. To that end, Fortinet announced that SoftBank will use Fortinet SD-WAN to expand its managed security services. SoftBank in Japan provides SD-WAN services to enterprise customers.

SoftBank will provide advanced security services, network analytics, and cloud on-ramp connectivity to enterprises. Maddison said Fortinet's SD-WAN portfolio for carriers is faring well as many are choosing to pull back from software-defined approaches to integrated hardware and software security appliances to improve performance.

In its just reported third quarter, Fortinet delivered a net income of 46 cents a share on revenue of $547.5 million, up 21% from a year ago. Ken Xie, CEO of Fortinet, said that the company saw strong growth in its security fabric, cloud, and SD-WAN offerings.

For fiscal 2019, Fortinet projected revenue between $2.13 billion and $2.15 billion with non-GAAP earnings between $2.39 and $2.41 a share.

Ensuring SCADA/HMI cybersecurity

2019-12-01T19:41:00.002+05:30

Critical industries, such as chemical, energy, transportation, and water/wastewater depend on supervisory control and data acquisition (SCADA) systems for daily operations. Strengthening weaknesses in these systems must be a priority and is a shared responsibility.

The U.S. Dept. of Homeland Security (DHS) has identified 16 critical infrastructure sectors that are "so vital to the United States that their incapacitation or destruction would have a debilitating effect on security, national economic security, national public health or safety, or any combination thereof." These include the chemical, critical manufacturing, energy, nuclear, transportation systems, and water/wastewater sectors.

According to a DHS report from the National Cyber Security and Communications Integration Center and Industrial Control Systems Cyber Emergency Response Team (ICS-CERT), the ICS-CERT team responded to 295 cyber incidents in U.S. fiscal year 2015, a 20% increase over the previous fiscal year. This included 95 incidents within critical manufacturing, 46 within the energy sector, and 25 within the water and wastewater systems sector.

These industries rely heavily on supervisory control and data acquisition (SCADA) networks for day-to-day operations. If national security is only as strong as its weakest link, the SCADA networks in our critical infrastructure might be that weak point. Strengthening the weaknesses in these systems must be a priority and is a shared responsibility.

The U.S. government has issued several guidelines and recommendations to help secure these critical industries, but most are vague and unenforceable. More than 85% of U.S. critical infrastructure is privately owned or operated, so it is largely up to the infrastructure operators to prepare action plans of prevention, mitigation, incident management, and response.

Why industrial networks are so vulnerable

Many of these SCADA systems have been running for decades. This legacy equipment was designed for the needs of the operational technology (OT) department, rather than the information technology (IT) department. IT and OT traditionally have had different priorities when it comes to security. IT is tasked with protecting a company’s data, so confidentiality is the main concern. The OT world was designed for ease of use, data availability and integrity, and uptime, but not necessarily for security.

When programmable logic controllers (PLCs) were introduced to the market decades ago, they solved a specific set of problems: easy maintenance in the field, high uptime, and a life span of 20 to 30 years. In the past, this was fine, because PLCs in the field were typically air-gapped, or isolated from other zones. However, in today’s connected world, this isolation is no longer the case. Even an air-gapped, stand-alone system is vulnerable to infection from a universal serial bus (USB) device.

Industrial protocols also present risks because they were not designed with security in mind. Because many of these protocols have been in use for decades, it would be a daunting task to add security at this point. It would require coordinating updates with hundreds of vendors who manufacture products for those protocols and ensuring interoperability of the devices installed around the world.

The growing use of industrial PCs (IPCs) and other human-machine interfaces (HMIs) leads to more vulnerability. While the IPC is built to withstand industrial conditions, it still might be running a commercial version of Windows, so it is susceptible to all of the vulnerabilities that come with that operating system. At least one out of three devices is still running Windows XP, which Microsoft no longer supports. Running antivirus software is difficult and expensive to maintain in an industrial environment, so if a virus infects an IPC, it could affect an entire system.

Where to turn for cybersecurity guidance

Both the public and private sectors understand how important it is to increase the security of these systems. In February 2016, the White House established a Commission on Enhancing National Cybersecurity with the goal of strengthening cybersecurity in both the public and private sectors. In addition, many industries have formed cyber security awareness groups to share experiences about the importance of cybersecurity, develop recommended practices, and create guidelines to show asset owners how and where to start taking responsibility for security in their networks.Examples include:

These guidelines rely heavily on Recommended Practice: Improving Industrial Control Systems Cyber Security with Defense-in-Depth Strategies, a report from DHS, originally released in October 2009 and updated in September 2016.

Steps to take to protect SCADA and HMI

A defense-in-depth methodology recommends taking a layered approach to cybersecurity. If there is only a single layer of defense, an intruder who knows how to get around that level can easily breach the entire system. For example, if the only level of defense is antivirus software, a new piece of malware that has not been detected can slip through the cracks because the software does not recognize it. Adding multiple layers of defense to a control system will minimize the risk of a serious incident.

Consider the following best practices for adding defensive layers to a control system:

Firewall management: Firewalls should be deployed throughout the control system network, including device-level firewalls at the remote terminal unit (RTU)/PLC/distributed control system (DCS) level (see Figure 1). The potential downsides of this practice are added latency and capital costs, but device-level firewalls will help isolate the infected or disrupted system if an attacker is able to gain access. For key access points, it is also smart to install multiple firewalls from different manufacturers. If an attacker manages to break through one firewall, there still is an additional layer of protection and additional time to patch vulnerabilities.

There are several different types of firewalls, and each has its pros and cons.

Packet filtering firewalls check the address information in each packet of data against a set of criteria before forwarding the packet. While they have low latency and cost the least, they also offer the lowest level of security.

Stateful inspection firewalls track active sessions and use that information to determine if packets should be forwarded or blocked. Even with the added security, stateful firewalls are still available at a cost-effective price point and do not add significant latency to the network.

Deep packet inspection (DPI) firewalls examine each packet at the application layer and provide the highest level of security. They add latency and are difficult to configure and maintain, so they should be used only in strategic points within an industrial network. They are more common in IT networks, where latency is not as much of a concern.

Security information and event monitoring (SIEM) technologies: SIEM technologies streamline the review of logs, simple network management protocol (SNMP) traps, and event management. SIEM technologies provide a central console for security personnel to review logs from intrusion detection systems, firewalls, and other cybersecurity devices. This can help users comply with monitoring, logging, and review requirements.

Demilitarized zones (DMZs): A DMZ is a protected subnetwork between two other networks (see Figure 2). It can be set up between an untrusted network (e.g., the office network) and a trusted network (the control network). There are several ways to create a DMZ network, but the purpose is to make data from the trusted network available to those who need it and who don’t necessarily need direct access to the network.

Patch management: As mentioned earlier, security patch management is difficult within legacy industrial control systems, but performing it can fix bugs and close vulnerabilities. Test these patches on a regular basis—at least once a year but more often in some cases—in a controlled environment, before applying the updates to all individual devices. After patches are tested, verify those results with the appropriate vendors.

Authentication and authorization: Authentication is a verification process to ensure that only those people, devices, systems, or other entities with the proper credentials can access the network. It is often used along with authorization, which specifies who has rights to access data. Technologies and practices to enable authentication and authorization include

Role-based access control

Challenge/response authentication

Physical token/smart-card authorization

Biometric authentication.

Malicious code prevention: There are several ways to detect, deter, and mitigate malicious code from infecting a network:

Antivirus software can be a valuable tool that can detect many viruses, but at the rate malware is being introduced, it is difficult to keep up-to-date, especially in an industrial setting. Another downside is that every IPC must have a unique license per operating system, so the costs can add up quickly.

Common internet file system (CIFS) integrity monitoring supplements antivirus programs in Windows-based systems and can detect malware on day zero. CIFS integrity monitoring examines file systems to take a baseline snapshot of what the system looks like when it’s clean. Most OT devices are static and have little change. CIFS integrity monitoring goes back on a regular basis to monitor whether anything has been modified. If it detects a change, it notifies the appropriate user. It also prevents installation of third-party software (see Figure 3).

Whitelisting allows the administrator to ensure that only trusted applications can run on the system. To work properly, it requires some administration, but it can prevent malicious files from running.

Virtual LANs: Another technology that can be deployed in networks is virtual LANs, or VLANs. VLANs physically divide networks into smaller, more logical networks to help increase performance and simplify management of the network. A VLAN is actually a network management tool and not designed to detect network security or vulnerabilities. A properly designed VLAN can help mitigate broadcast storms that may occur from hardware failures or cyber incidents.

Data diodes: Data diodes are another access control technology that can be deployed in control system networks. For traffic that needs to be only unidirectional (e.g., operational data being sent to a backup location), a data diode can ensure that no return traffic is allowed back into the protected system. A data diode is a system in which a pair of devices works together; one device has only a physical transmitter while the other has only a physical receiver. Software within the system handles the generation of transmission control protocol (TCP) acknowledgments that are required for many communication protocols.

Encryption technologies: The ISA 99 standard recommends the use of virtual private networks (VPNs) to secure remote connectivity. A VPN allows private networks to communicate over a public infrastructure. It encrypts data across untrusted networks and authenticates access into trusted networks.

Common-sense best practices: Technology is critical in securing control systems but doesn’t overlook the human level. SCADA and plant managers need to cultivate a security culture, similar to the safety culture that has become more common over the past decade. Managers should look at the logs and audit them regularly. Set a policy that requires strong passwords and teach employees how to create them. Never use the device’s default password.

Securing the future

Nearly every day, reports are published that prove how fragile and vulnerable networks are, including SCADA and the operating systems running in ICS. These reports explain new cyber-attacks, viruses, vulnerabilities, and even zero days in detail, which can either push the vendor to fix the problem by pushing out security updates or allow attackers to exploit them. ICS cybersecurity is very important, as we count on these systems to bring electricity, clean water, communication, entertainment, and more to our homes.

The implementation of the methods mentioned above, like a multitiered, defense-in-depth approach, addresses the cybersecurity gap in our critical infrastructure, but there is no single entity responsible for the entire process. Other than the energy industry, no other industry regulations are mandatory, therefore the level of protection depends largely on budgetary restrictions in the organization.

An IT administrator’s goal is to maintain the highest level of protection possible in his or her network and systems without interfering with everyday business in which OT engineers must keep the ICS process available and running. At the same time, because both groups must comply with corporate policies, a centralized way to monitor security and manage the network and OS can make their jobs easier and more flexible and efficient. OT, IT, company management, government, and others must play on the same team to ensure that our networks stay secure, available, and accurate.

Mariam Coladonato is the product marketing specialist for networking and security at Phoenix Contact USA. She has worked at Phoenix Contact, supporting the FL mGuard product family, since 2012. Coladonato has a degree in electrical engineering from West Virginia University Institute of Technology, and she is currently pursuing a master’s degree in cybersecurity.

This article appears in the Applied Automation supplement for Control Engineering and Plant Engineering.

PLC BASICS

2019-08-20T18:06:00.000+05:30

Today we are going to talk about PLC basics. The programmable logic controller, or PLC, is a special purpose computer. It has no display, no keyboard, no printer, no hard drive, and hides in the control panel out on the factory floor, but it is still a computer.

Initially, the PLC was a replacement for panels of relays, devices that turn on and off. Making a machine run using relays as logic was time-consuming and challenging, and making a change in the logic or the operation of the machine was almost as complicated as starting over.

Relays also fail far more frequently than computer components, so that relay logic required more downtime to keep it running than newer PLC-based controls.

On top of all of that, relays use a lot of electricity, make lots of heat and soot, and take up lots of space.

An installed PLC is deceptively simple in appearance. You have a CPU module and input/output devices, referred to as I/O. Sometimes the I/O is part of the CPU, and sometimes it is in other modules.

The CPU communicates with the I/O, so in most systems they share a backplane that physically holds them in place and electronically connects them.

In other equipment, the I/O modules can be miles away from the CPU and connected with data cables, so that the PLC is not limited to a single cabinet or even the same building. Since the PLC is a computer, there is no need to limit it to only digital inputs and outputs. Over the years, the manufacturers added analog and other numerical inputs and outputs.

To make these numerical devices useful, they included calculation capability in the programming as well, so that we can now calculate, for instance, statistical process control (SPC) values and put PID controllers directly into the PLC program.

Since this is called a programmable logic controller, we need to program it. Most PLCs are programmed using an application running on a standard desktop or laptop PC.

They communicate with the PLC using Ethernet or a proprietary communication bus, depending on the manufacturer. Most manufacturers seem to have settled on Ethernet and/or USB in recent years.

Unfortunately, the PLC manufacturers have failed to agree on how we program the control logic. Although most of the manufacturers claim some form of “Ladder Logic,” the specifics of that language are different for each manufacturer, including different capabilities, different ways of doing the same thing, and even differences in the order in which the CPU processes the various pieces of logic.

One attempt to bring some order and inter-operability to this chaos is the IEC 61131 standard from the American National Standards Institute (ANSI). The excerpt from the ANSI web page gives a flavor of what is there.

The IEC 61131 standard defines several “programming languages” with different strengths and weaknesses. Local programming standards – your boss or the customer – will usually specify what language you use.

That wraps up this short discussion of the structure of PLCs – I hope you enjoyed this little introduction to the underlying architecture of many industrial control systems. Keep watching as we continue our exploration of the basics of industrial controls.

I hope this video has helped you. Make sure to check back later for more awesome videos!

Thank you so much for watching, sharing and continuing to be a part of our world.

With so much love and excitement,

The RealPars Team

PLC ANALOG INPUTS AND SIGNALS

2019-08-20T17:39:00.001+05:30

Welcome to another to another blog post on industrial automation and PLCs. In this lesson, we are going to be talking about PLC Analog Inputs.

What do we mean by PLC analog inputs?

Analog values are continuous values, such as temperatures and pressures.

While we tend to think of them in digital terms, at some point we have to convert them from the continuous world into our digital world, and this is where PLC analog inputs come in.

Voltage signals in the range of plus or minus 20 volts or so and current signals in milliamps are commonly used as both analog inputs to PLCs.

Every PLC manufacturer has I/O modules to deal with these kinds of signals, along with other, more specialized modules.

The simplest of these types is the voltage input, so we will tackle it first.

Voltage-Mode Analog Inputs

In the image below we have a simple circuit that converts the position of a 0 into a 0 to 5 volts signal and connected to a generic PLC voltage analog input.

When the knob is on zero, the input to the PLC will be zero volts, and at the other end of the knob’s rotation, the PLC will see 5 volts.

What the PLC program sees as the result of the conversion of the voltage to a number depends on the PLC and its configuration.

For instance, some of the older Allen-Bradley SLC models would return an integer ranging from 0 to 8191 for an input of 0 to 5 Volts.

Usually, the newer models of PLC will allow more flexibility in how the value is returned, so that you can scale the numeric value to whatever your application needs.

The PLC program can use this input to control (for example) the brightness of a light bulb, the output of a heat source, the speed of a motor, or how fast a counter counts.

Current-Mode Analog Inputs

While the voltage input is capable of almost everything we need in general applications, because of electrical noise interference from other devices, current mode signal transmission is a better choice for signals that need to travel over any real distance. For this reason, many applications use current inputs.

From the PLC end, a current mode interface is generally a voltage mode interface with an added high-precision resistor.

While the resistor is often inside the PLC module and switched in by a jumper or connection position, it is effectively the same.

Below you can find an example of a device powered current source. The field device is getting its power from another source.

The current signal is sourced from the positive terminal on the measuring device, traveling to the positive terminal of the PLC.

Since there is a limit to how much voltage is available in the loop; we usually limit the overall resistance on the measuring end of the loop to 500 Ohms. Often this is called out as part of the field device installation instructions.

Another common type of analog device uses the 4 to 20 milliamps signal as its power source, reducing the required complexity on the field end.

Below is an example of a “loop-powered” arrangement. The main addition to the circuit is the separate power supply on the PLC end.

Note that the positive and negative measuring device connections are different from the previous example.

The current comes from the power supply in the positive terminal of the loop-powered device and out the negative terminal and into the positive PLC terminal.

What we have covered so far have been generalized inputs, used where the field signal is set up as a conditioned input for the PLC.

The next types of inputs we will cover are specific to two different types of common temperature measurement devices that are common enough to be worth building specific modules for. There are thermocouples and resistance temperature detectors (RTDs.)

Thermocouple Inputs

The older type of temperature device is a thermocouple.

This type of device generates a small signal, in the millivolt range, depending on the temperature at the “junction” the point where two different metals touch to create the voltage.

A thermocouple measurement module is designed to process these tiny signals into temperature readings, and they have several somewhat picky features.

The wires used to connect the thermocouple to the module must be made specifically for that type of thermocouple – the wrong kind of wire will make the signal useless.

Because the signals are at such a low voltage, the wires need to be well shielded and carefully routed away from higher voltage wiring.

Finally, these sensors need “cold junction compensation,” a feature which is built into most thermocouple modules, but some require external devices for this purpose.

The temperature range of a thermocouple is specified by a single letter, I.e., a “Type J” thermocouple is a common variety with well-known characteristics.

RTD or Resistance Temperature Detector Inputs

The newer RTD or resistance temperature detector is generally more robust and accurate than the thermocouple, but the older sensors are still quite common because they are both designed into older equipment, and capable of operating at temperature ranges that RTDs are not made to handle, including up to white heat(1600°C) in unique applications.

As the name implies, the resistance of the device changes with its temperature, so measuring the output is relatively straightforward.

They generally come in three- and four-wire configurations, and several temperature ranges.

This lesson has been a basic introduction to the most common sorts of analog inputs used in PLC-based applications.

Each of the types covered here has its quirks, and the ways the PLC analog inputs are built differ between manufacturers and PLC models, so we have just covered general principles without enough detail to implement them in any given PLC system.

We have also not attempted to cover every type of device. Each manufacturer has unique ways of handling measurements, and there are many other sorts of sensors that we have not included here.

We at RealPars hope you have enjoyed this introduction to PLC analog inputs, and hope that you will come back and watch our other automation lesson.

We are working diligently to cover more topics and improve the information available, so feel free to let us know if you want us to include a specific topic.

We hope that you found it interesting, and that you will come back for more of our educational blogs. share your thoughts and ideas directly in the comments.

See you next week,

The RealPars Team

WHAT IS LADDER LOGIC?

2019-08-20T17:37:00.001+05:30

If you are involved in any way with industrial machinery, you almost have to have heard of ladder logic. Since there are almost never ladders involved, it probably doesn’t make a lot of sense that we call it that, but the reasons for the name are buried in the history of automatic controls.

At one time, automatic systems were controlled with relays.

Relays are electromechanical devices and fail quickly as the mechanical parts wear out and the electrical parts are destroyed as the electricity they switch burns away the contacts.

They are big and use lots of electricity, generating lots of heat in the process.

At one time, the only “automatic” device most people ever encountered was an elevator.

In modern-day control terms, the elevator is a simple application that is well understood.

Even so, a control system implementation in relays was a big, complicated affair.

In order to understand why we call it ladder logic, you need to look at how we document relay logic controls.

The actual “ladder” was the drawing of the control logic, an illustration of how the relays were wired together. Even today, a lot of the conventions that led to “ladders” are still in use, and I will use a recent example drawing to illustrate this.

Below is a simplified drawing of a control circuit. The appearance is what led to being called ladder logic, since it superficially resembles a ladder.

Other drawing conventions that survived into the software version include:

Power at the top of the drawing, with the hot or power rail going down the left side, and the neutral rail going down the right side.

We also have contacts or inputs on the left, and coils or outputs on the right, so that our power is flowing from left to right.

Finally, each of the outputs is on a separate horizontal line or, in our ladder metaphor, rung.

Another convention is that we always descend the ladder – we work from top to bottom.

Relays are simple devices, consisting of coils and the contacts that they move. When electricity energizes the coil, it moves the contacts, connecting some and disconnecting others. The lowest-level elements of ladder logic mimic those relay functions.

Below is an example of the logic from the example drawing I have been using, rendered in Rockwell Software’s Studio5000.

Output contacts on real-life relays are usually called normally open and normally closed.

Normally Open means that when the relay coil is not powered (”normal” for a relay) the contact is open, or not conducting. Normally closed is the opposite – when the relay coil is off, the contact is on or conducting.

So below is our software representation of a “normally open” contact.

The drawing symbol and the symbol in the software are pretty much the same. Normally closed contacts are also very similar, just a representation of two separated contacts.

Finally, the relay coil – not quite a full circle like the drawing, but close enough to get the point across.

For the things we have described so far to be useful, they have to make other things happen. For instance, if the machine is ready to run and we push the auto start button, we want the machine to start continuously running until we push the auto stop button.

Here is our English sentence written in ladder logic.

Let’s take that picture apart. And look at the English with it. If the machine is ready to run – we have a contact called “ReadyToRun” – AND we push the Auto Start button – “AutoStart” contact, with the two contacts in series so that if both of them are on, then we energize the “AutoRunning” coil.

When we energize the AutoRunning coil, that also energizes the AutoRunning contact, which keeps the AutoRunning coil energized – “continuously cycling” – until we push the AutoStop button. Since that is a normally closed contact, when we push the button, it STOPS conducting, which de-energizes the coil.

The circuit we just drew in ladder logic, and the one that we could have drawn on paper, is in thousands of motor starter panels all over the world. They add stuff to it, but the basic circuit and meaning are the same – push the start button, the motor runs until you push the stop button.

Ladder Logic

Paper

Welcome to real world ladder logic. Since the real world is more complicated than just on and off, we need some more complicated functions to deal with it. One of these was in the original drawing I started this off with, and I wanted to come back and cover it.

One of the most common functions other than on and off is a time delay, something that waits a specified period of time before turning on or off. We had one in this drawing, although its output isn’t specified. We call these timing relays when we use them in a circuit like this drawing.

In the ladder logic program, we must specify all the different needs for a timer. In our Allen Bradley ladder logic, we have an on-delay timer which is labeled TON.

The amount of time it delays is specified in milliseconds, so the half-second timer in our example becomes 500 milliseconds.

These sorts of more complex functions are what we call function blocks in ladder logic programming. The functions contained in these blocks and how they operate very between PLC manufacturers, and even within a given manufacturer’s PLCs, they may differ.

So, this ends our introduction to the history of ladder logic, and how it got its name. As the history of these systems recedes further in the rearview mirror, is always helpful to look back and see where we have been.

We at RealPars hope that you found it interesting, and that you will come back for more of our educational blogs.

With so much love and excitement,

The RealPars Team

WHAT IS A PID CONTROLLER?

2019-08-20T17:36:00.002+05:30

Today you will learn about PIDs. Specifically, what they are and when do we use them with automation and PLCs.

So what is a PID controller? PID is an acronym that stands for Proportional, Integral, Derivative.

If you need to keep something constant, like a temperature for example, then this is the way to do it.

Essentially, PID Controller uses a control loop feedback to ensure the output wanted is what you will get.

Simply, you put a setting in the controller and it will keep the output constant based on feedback from some input, typically some kind of sensor.

Something you probably encounter every day that is essentially PID control is your cruise control in your vehicle.

First, you get to the speed that you want to be going. Then you set your cruise control. The cruise control sends output signals to your throttle to regulate the speed.

A speed sensor provides your control loop feedback to tell the cruise if the car should speed up or slow down, or how much more or less throttle to provide.

A common standalone type that we use in manufacturing and industry, is a “Temperature Controller PID”.

These controllers are pretty simple to use and setup, plus they do a great job at controlling temperatures of a variety of equipment.

For our example, we will look at a PID controller that controls the temperature of heat tracing on process piping.

First, we need to enter a set point, 200 degrees Fahrenheit for our example.

Now the controller will give a signal to the output to start heating up the heat tracing.

The control loop feedback is in the form of a thermocouple to read the temperature. For our example, the PID controller can work as on-off control for the heat tracing.

Along with the set point of 200 degrees, we will set the controller at a couple of degrees above and below 200 as well.

When the thermocouple reads 202 degrees it will turn the heat tracing off.

When it reads 198 degrees it will turn it back on.

This is the simplest form of PID control.

We also have the option of setting up a PID controller with a PLC. Instead of the standalone unit, we can use the input and output cards already on our PLC.

The process variable, or control loop feedback, would be wired to our input card and programmed into the PID. Our output being controlled is wired to our output card.

The PID in the PLC can do all of the math and make the decisions based on the variables and set points.

No matter which way you decide to set it up, a PID is an excellent choice for an automated process.

In summary, A PID controller is a Proportional, Integral, Derivative controller. It can keep an automated process like temperature, pressure, or flow, constant, for you automatically.

PIDs use a control loop feedback or process variable to monitor where the output should be. These usually come in the form of sensors and meters.

PIDs come in many different forms including standalone units and PLC programming.

We can use our input and output cards along with programming software to set up a PID.

I hope this article really helped you get a grasp of how to use a PID.

Thanks again for reading. Leave your questions and comments and we’ll chat with you soon!

Happy learning,

The RealPars Team

WHAT ARE THE MOST POPULAR PLC PROGRAMMING LANGUAGES?

2019-08-20T17:35:00.001+05:30

There are 5 languages that are all a part of the IEC (International Electrotechnical Commission) Section 61131-3 Standard. This IEC Standard allows some ground rules that standardize PLC’s and their languages. Let’s take a deeper look into all these PLC Programming Languages.

The 5 most popular PLC Programming Languages are:

1. Ladder Diagram (LD)

2. Sequential Function Charts (SFC)

3. Function Block Diagram (FBD)

4. Structured Text (ST)

5. Instruction List (IL)

Let’s show you a little bit about each of these. I will start with Ladder Diagram which is a graphical type of PLC Programming Language.

1. Ladder Diagram (LD)

Ladder Diagram was originally modeled from relay-logic which used physical devices, such as switches and mechanical relays to control processes. Ladder Diagram utilizes internal logic to replace all, except the physical devices that need an electrical signal to activate them.

Ladder Diagram is built in the form of horizontal rungs with two vertical rails that represent the electrical connection on relay-logic schematics.

You can program all the necessary input conditions to affect the output conditions, whether logical or physical.

1-1. Ladder Diagram Advantages

The main advantages of the Ladder Diagram language are:

1. The rungs allow it to be organized and easy to follow.

2. It also lets you document comments that are readily visible.

3. It supports online editing very successfully.

1-2. Ladder Diagram Disadvantages

The main disadvantage is that there are some instructions that are not available, which might make it more difficult for programming such as motion or batching.

The next PLC Programming Language that I will talk to you about is the Sequential Function Charts which uses a graphical type of programming.

2. Sequential Function Charts (SFC)

If you have any experience with flowcharts, then this PLC Programming language will feel familiar to you. In Sequential Function Charts, you use steps and transitions to achieve your end results.

Steps act as a major function in your program. These steps house the actions that occur when you program them to happen. This decision can be based on timing, a certain phase of the process, or a physical state of an equipment.

Transitions are the instructions that you use to move from one step to another step by setting conditions of true or false.

Unlike traditional flowcharts, the Sequential Function Charts can have multiple paths. You can use branches to initiate multiple steps at one time.

2-1. Sequential Function Charts Advantages

A couple of the advantages of Sequential Function Charts are:

1. Processes can be broken into major steps that can make troubleshooting faster and easier.

2. You have direct access in the logic to see where a piece of equipment faulted.

3. It can be faster to design and write the logic due to the ability to use repeated executions of individual pieces of logic.

2-2. Sequential Function Charts Disadvantages

Even when you consider the advantages of the Sequential Function Charts, this PLC Programming Language does not always fit every application.

Now we are on to our third PLC Programming Language.

3. Function Block Diagram (FBD)

The Function Block Diagram which is also a graphical type of language. The Function Block Diagram describes a function between inputs and outputs that are connected in blocks by connection lines.

Function Blocks were originally developed to create a system that you could set up many of the common, repeatable tasks, such as counters, timers, PID Loops, etc.

You program the blocks onto sheets and then the PLC constantly scans the sheets in numerical order or is determined by connections which you program between the blocks.

3-1. Function Block Diagram Disadvantages

The code can get disorganized using this PLC Programming Language because you can place the function blocks anywhere on the sheet. This can also make it more difficult to troubleshoot.

3-2. Function Block Diagram Advantages

1. The Function Block Diagram does work well with motion controls.

2. The visual method is easier for some users.

3. The biggest advantage of Function Block Diagram is that you can take many lines of programming and put it into one or several function blocks.

4. Structured Text (ST)

The 4th PLC Programming Language is the Structured Text. This language is a textual based language.

Structured Text is a high-level language that is like Basic, Pascal and “C”.

It is a very powerful tool that can execute complex tasks utilizing algorithms and mathematical functions along with repetitive tasks.

The code uses statements that are separated by semicolons and then either inputs, outputs, or variables are changed by these statements.

You must write out each line of code and it uses functions such as FOR, WHILE, IF, ELSE, ELSEIF AND CASE.

If you have experience with Basic or C languages, this PLC Programming Language will come easier than some of the other languages.

4-1. Structured Text Advantages

Some of the advantages of Structured Text are:

1. It is very organized and good at computing large mathematical calculations.

2. It will enable you to cover some instructions that are not available in some other languages like the Ladder Diagram.

4-2. Structured Text Disadvantages

The disadvantages of the Structured Text PLC programming language are:

1. The syntax can be difficult.

2. It is hard to debug.

3. It is difficult to edit online.

5. Instruction List (IL)

I will now show you the 5th and final PLC Programming Language which is Instruction List. The Instruction List is also a textual based language.

The Instruction List language resembles Assembly Language. When you use this PLC Programming Language, you will use mnemonic codes such as LD (Load), AND, OR, etc.

The Instruction List contains instructions with each instruction on a new line with any comments you might want to annotate at the end of each line.

5-1. Instruction List Advantages

The Instruction List language is valuable for applications that need code that is compact and time critical.

5-2. Instruction List Disadvantages

The main disadvantages of this PLC Programming Language are:

1. There are few structuring possibilities with the “Goto” command being one of them.

2. There can also be many errors that are more difficult to deal with in comparison to many of the other languages that I have previously reviewed.

So, have you decided which PLC Programming Language you consider to be the most popular?

After reading many reviews and opinions and with my own experiences, the Ladder Diagram is by far the most popular PLC programing language .

The main reason for this is that the Ladder Diagram language naturally followed the technology advancement from a physical relay logic to a digital and logical one. This allowed the engineers and skilled workers to follow and troubleshoot and make that transition.

In summary, there is certainly a place for all the PLC Programming Languages that we have reviewed. Your background, experience and the application you are working with are really going to be the key to which PLC Programming Language you choose.

What’s the biggest “aha” you’re taking away from this technical conversation? How can you put that insight into action now? Tell us the comments below.

Thanks again for reading. Leave your questions and comments and we’ll chat with you soon!

Happy learning,

The RealPars Team

WHAT ARE THE MAJOR PLC MANUFACTURERS?

2019-08-20T17:33:00.000+05:30

Today we will discuss several of the top PLC manufacturers from around the world. There are quite a few, and hopefully this video will clear up some of the differences of the major brands.

As technicians, engineers, and programmers, we have several choices when it comes to choosing a brand of PLC. Depending on where you work, you may have to familiarize yourself with many different PLC brands.

Some places use more than one manufacturer in a single facility. So let’s break some of the major brands down so we can see the difference.

1. Siemens

Probably the biggest name out there in the automation and PLC world is Siemens.

Siemens offers their SIMATIC line of controllers, giving users of all performance needs an option.

SIMATIC stands for Siemens Automatic. The name itself should be an indicator of it’s role in automation and manufacturing.

Their SIMATIC controllers have some pretty great standard features, including Ethernet TCP/IP easy connections and for Profinet IO communications. Profibus is included or easily added with a module.

When it comes to the SIMATIC software, Siemens claims that they offer maximum efficiency throughout the automation process. Their SIMATIC STEP7 lets users configure, program, test and diagnose the basic, advanced and distributed controllers.

Programmers and engineers from around the world are familiar with the Siemens platform making it a solid choice for any company.

2. Allen-Bradley

One of the largest PLC manufacturer used in the United States is Rockwell Automation and their Allen-Bradley line of controllers.

Allen-Bradley offers controllers for all different sized projects. Their large control systems are being referred to as Programmable Automation Controllers or PACs. These are made with a complete automated project in mind.

A network of their large controllers can essentially run an entire plant with proper design and planning.

This is accomplished with their ControlLogix controllers and software, GuardPLC for safety systems, and SoftLogix software suite.

Allen-Bradley also offers systems for smaller applications. Most popular are their MicroLogix, SLC500 /slik five hundred/ and CompactLogix systems.

All of these are still extremely powerful for the needs of almost any industry. Every manufacturing facility that I have ever worked in had several of each of these controllers installed in their equipment.

The programming for Allen-Bradley controllers comes in the form of RSLogix 5000 and the newer Studio 5000.

The RSLogix line of programming software has been around for many years and has progressed into an extremely powerful automation tool.

If you were to search for a job dealing with PLCs in the United States, there is a pretty good chance it will require knowledge of RSLogix and Allen-Bradley.

3. ABB

Another well known and high end PLC manufacturer is ABB. ABB offers their AC500 lineup that caters from small to large high end applications.

One aspect of the AC500 line that sets it apart from some of the other brands is their concept of “any module in any CPU”.

This means that no matter what CPU you have for your AC500 PLC, you can use any ABB AC500 module. This makes finding replacement parts easy and affordable.

One common factor between all three manufacturers that we have discussed is the option of modular devices. All of these brands let the customer set up their system as they see fit. You can add as many input cards or output cards or combination of cards as you need for your application.

They also offer fixed units in their smaller applications. This means that the fixed PLC may have a set number of inputs and outputs built in to the unit. These are usually less expensive and great for small applications.

Another thing to remember about each of these brands is that they have the parts for an entire project. From the PLC to the HMI to the switches and motor drives. All three brands make all of the components to complete the project.

Let’s look back at what we now know. Today, we have discussed three of the major PLC manufacturers.

Probably the most well known around the world is Siemens. Siemens offers something for all applications, big and small.

One of the largest and most well known in the United States is Allen-Bradley by Rockwell Automation.

Their RSLogix programming software has been around for a long time. The latest version is it’s Studio 5000.

Lastly, ABB is another PLC powerhouse. They have been in the automation arena for many years as well. Their AC500 line has anything you would need for a project.

Just remember that all three brands can complete an automation project from start to finish with hardware and software.

Remember that there are plenty of other manufacturers out there as well. A simple search can lead to tons of information.

I hope this has been a helpful lesson that sheds some light on what all is out there. Please check back soon for more RealPars blog post!

We at RealPars hope that you found it interesting, and that you will come back for more of our educational blogs. share your thoughts and ideas directly in the comments.

See you next week,

The RealPars Team

WHAT IS RTU?

2019-08-20T17:31:00.002+05:30

RTU stands for Remote Terminal Unit, sometimes also called Remote Telemetry Unit or Remote Telecontrol Unit.

A RTU is a microprocessor based device that monitors and controls field devices, that then connects to plant control or SCADA (supervisory control and data acquisition) systems.

If you do a search on the definition of a RTU, you may find many results that state a RTU is much more powerful than a PLC as the RTU can have several inputs and outputs. Well, as you know, so can the PLC.

The RTU does have some potential benefits over the PLC, which we will discuss.

Price Point

On the price point, the winner right now is the PLC.

PLCs have a lower price point but many consider the RTU to be a much more rugged system which would lead you to believe that spending more initially will equal out in the end.

Process Control

As far as process control, the RTU is probably on equal ground with the PLC. Both controllers can have multiple different types of I/O, different communications modules, and programming of processes that may require little to no operator intervention.

Where the RTU is considered to have some advantages is in environment tolerances, backup power options, and autonomy.

Programming Advantage

Let’s first discuss a programming advantage that the RTU may have over the PLC.

A PLC requires specific software and specific skills and knowledge of ladder logic, structured text, function block, etc.

A RTU can sometimes be programmed through a simple web interface. In other instances, the RTU comes with setup software that can help you to configure input streams to output streams as well as communications.

There are also many RTU’s that have preprogrammed modules that can just be applied for the desired function.

This advantage can quickly be turned into a disadvantage.

Some RTUs may be programmed with languages such as Basic, Visual Basic and C#. Of course, these languages require a special skill set just as the PLCs do.

Some RTUs are even programmed in the same languages that PLCs are programmed with such as Ladder Logic and Structured Text.

Environmental Tolerances

A definite advantage is in the environmental tolerances of a RTU.

RTU’s are widely used in environments with extreme temperatures and located in remote locations.

And when I say remote, I don’t mean within a few feet or few hundred feet, I mean miles down dirt roads, on top of mountains, on off shore oil rigs, that kind of remote.

Imagine using a RTU on an off shore oil rig. Getting reliable communications would be both essential and difficult. With the use of the stated communications, sending and receiving data from these very remote locations is a breeze.

Some RTU’s have a backup battery and charging circuit, such as solar power, that will allow the RTU to continue to operate even when AC power is lost.

Of course, PLC’s can have a UPS backup which adds the same benefit but the charging circuit is a definite plus.

The advantages that were described here can easily be mitigated with the new PLC and PAC (programmable automation controller) systems. Just about every category of advantage can be found in other options.

The biggest advantage is the environmental tolerances, those are hard to compete with.

So all and all, there aren’t a lot of differences between modern RTUs and PLCs.

The ever changing technologies do a remarkable job of leveling the playing field.

With so much love and excitement,

The RealPars Team

WHAT ARE THE ADVANTAGES PLCS HAVE OVER RELAY SYSTEM?

2019-08-20T17:30:00.003+05:30

There are many advantages that a PLC system holds over a relay system. Today, we will dive into some of those advantages. One of the first and simplest advantages is reliability.

1. Reliability

The internal relay systems of a PLC are solid state. This means that the relay function is not mechanical like conventional relay systems and components.

Traditional mechanical relays wear out much faster than the electronics in a solid state relay. Every time a mechanical relay opens and closes, the contacts will arc slightly. The arcing can eventually destroy the contact. This is simply not the case with the solid state type relays found in our PLC systems.

2. Ease of Troubleshooting

Another advantage of a PLC system is the ease of troubleshooting. In a PLC system, a good technician can read through the programming and usually figure out what is and isn’t working.

In a relay system, there will be several more wires plus the relays and possibly other components that aren’t needed in a PLC. This makes finding problems much harder.

Each physical relay needs a minimum of four wires to operate and function.

A relay output card on a PLC sends out one wire to the output device.

You can only imagine how much easier it is to troubleshoot the PLC system with multiple outputs versus the relay system with four times the number of wires.

3. Easy Expandability

One of the best features that a PLC system has over a traditional relay system is versatility with the programming and easy expandability. For example, if you wanted to add a timer to make a motor turn on after five seconds, you would just add it to the program and set it to five seconds in the PLC.

For a relay system, you would have to add an entirely new physical component. On top of that, you would have to add all of the proper wiring to make that timer work for the specific motor. This also makes expanding a system much cheaper. Not only for component costs but labor savings as well. If you have a relay system, someone will have to be paid to install a wire all of the new components.

4. Smaller Size

The physical size requirements of a PLC system are far smaller than a cabinet needed for relay logic circuitry.

Most of the physical relays, timers, counters, and controllers from a relay logic system are all contained in the PLC itself.

Depending on the machine, a cabinet containing the PLC can easily be a third of the size of a relay logic cabinet. Possibly even smaller.

Let’s look back at what we now know. PLCs are much more reliable and are way easier to troubleshoot.

The mechanical functions of relays simply wear out over time. Plus, the wiring required to operate a relay system is much more complicated than a PLC system. This can also cause higher costs to install and upgrade due to extra labor costs.

One of the major advantages is the versatility of a PLC with its programming and internal relays, timers, counters, among other features.

I hope you have enjoyed this newest installment from RealPars. Please check back soon for more useful videos. Thank you so much for your valuable time visiting our website. Please share your thoughts and ideas or questions directly in the comments.

With so much love and excitement,

The RealPars Team

WHAT IS AUTOMATION?

2019-08-20T17:22:00.001+05:30

So you have heard of automation or industrial automation a few times here and there and you’re wondering what it is and how it actually works. In this short video and blog post, that’s brought to you by RealPars, you’re going to learn what industrial automation is in a very basic and simplified way. Let’s get into it.

let’s say that I’m entering a room and it’s dark. What is the first thing that I should do when entering a dark room? Yes, I should turn the light on. That means I should manually press the switch on the wall and turn the light on.

Let’s say that instead of the wall switch, I’ll install a sensor in that room.

This sensor has a simple open contact within it, just like a normal switch. The way that this sensor works is that it always looks into the room and when it sees someone entering the room, the open contact is going to be closed and following that, the light is going to turn on automatically.

When the person leaves the room and there is nobody in there, the contact will be open again and this time the light will be turned off automatically.

So by having this sensor installed, I no longer need to press any switch on the wall when I enter or leave the room. With the new system, everything happens automatically on its own, meaning when I enter the room, the sensor kicks the light on automatically and when I leave the room and there is nobody else in there, the light automatically goes off.

If we consider turning on the light in the room a process, we can say that when I need to press the switch on the wall, the process is happening manually and when the light turns on and off on its own, when someone enters or leaves the room, the process happens automatically. So here I have manual vs automatic.

manual vs automatic

What is the difference between these two? Well, obviously the automatic way is more convenient for me, right? Because here I don’t need to press anything on the wall to turn on and off the light.

The automatic way is also more energy efficient. Because with this method when I leave the room and nobody else is in there, the sensor is going to turn off the light after a few seconds. With this method, I can expect to see some real energy savings here as well.

So this is a very basic example of a manual vs automatic process.

Let’s bring the same concept into a factory, the manual vs automatic concept. When we’re going to manufacture a product, there is always a start line and a finish line.

The start line is where the raw materials enter the factory and the finish line is where the final product is manufactured and ready to be shipped.

Between the start and finish lines, there is a process that turns the raw materials into that final finished product.

So here I have a process. The raw materials can be considered as the input for this process and the final product can be considered as the output or as the final outcome.

Just as the process of turning on and off a light, this process of manufacturing a product in a factory, can happen either manually or automatically.

For the manual process, we can hire a few workers to do the job but with the automatic way, we can put a system in place that is able to take care of the whole manufacturing process or at least some parts of it automatically.

For instance, let’s say that you’re going to start a cupcake business and you want to make your own cupcakes. To make the cupcakes, you’ll need a manufacturing process where all the necessary ingredients come in as the input and a delicious cupcake comes out as the output.

At the beginning of your business, when you’re on a tight budget and of course have fewer customers, you can hire one or more workers and train them to make the cupcakes based on your recipes.

With this limited manual manufacturing process in place, you may be able to make the cupcakes at a reasonable speed and with consistent quality. But as your business grows, trying to make more cupcakes manually with the high consistent quality will be very difficult. Why? Because humans make mistakes.

For instance, if one of your coworkers adds more of a one ingredient, that batch of cupcakes won’t have the same quality as the rest of the cupcakes and if this happens often, your business will start losing customers and eventually losing money.

What should you do to solve this problem? To solve this problem you’ll need to hire an engineering firm to help you turn this manual cupcake manufacturing process into an automatic process.

With the new automatic manufacturing process, you’re going to have fewer employees and more machinery. This means with the new system in place, your machines are going to take care of most of the jobs that were previously done by the workers and they are going to do it fast, hassle free and accurate.

So with the automatic process, you’re able to make more cupcakes with the same constant high quality and this helps your business grow faster.

The same principles apply to other industries such as automotive, steel or oil and gas. For these industries to be able to manufacture the final product based on the new standards, they need to have an up to date automatic manufacturing process.

So industrial automation is all about large scale processes, with a high degree of quality and consistent accuracy. When we need to manufacture a product on a large scale with consistent quality at the same time, we need to hire an engineering firm to design an automatic manufacturing process for our business or factory.

Thank you so much for taking part of your day to be here. Leave a comment to let us know what you think and make sure to subscribe to our newsletter to get the latest content first.

With Great Love,

The RealPars Team

HOW TO CONVERT A BASIC WIRING DIAGRAM TO A PLC PROGRAM

2019-08-20T17:21:00.001+05:30

Today you will learn how to convert a basic wiring diagram to a ladder logic PLC program. This can be a very handy skill to learn, especially if you are converting a machine to PLC control.

Upgrading a machine to PLC control may seem like a daunting task. However, if you take your time and learn the basics, it can be an easily achievable task.

Today I will walk you through programming a very basic “stop-start” circuit for an electric motor. This should help you get a handle on some of the basics.

First, let’s look at our basic start and stop diagram.

Tracing the Electrical Wiring Diagram

I like to start on the left side of the “start-stop” wiring diagram of the electric motor and follow the line. Each line represents a wire that is connected. I’ll go over each section based on the numbers that you see in the wiring diagram above. So for each section explained below, just look at the numbers and the arrows in the wiring diagram above. Ok?

1. L1 is our 120 Volts hot wire. It will run straight to the normally closed Stop button labeled PB1. It is the “Stop Push Button”.

2. From the other terminal on PB1, it runs to a normally open PB2 which is our “Start Push Button”.

3. From the other terminal on PB2, a wire connects to the A1 terminal on the “Motor Starter Coil”.

4. The A2 terminal of motor starter coil runs to the normally closed “overload auxiliary contact”.

5. The next wire runs from the other overload terminal to neutral.

6. The next line down shows how a motor starter stays energized. One wire needs to be connected to the input terminal of the start push button. It will run to one terminal of the auxiliary contact set on the motor starter. This ensures power is on the auxiliary contact.

7. The second terminal of the auxiliary contact is connected to the output side of the start push button.

When the start button is pushed, the circuit is complete and the motor starter will energize.

This closes the auxiliary contact and allows the operator to release the start button. The motor starter will now stay energized until the stop button is pressed and the circuit opens.

Now that you are familiar with the wiring diagram, let’s program it in ladder logic now. When you are finished, your program will look very similar to our wiring diagram.

Converting the Wiring Diagram to a PLC Program

Programming software is all different but similar. Most have a toolbox somewhere that you will drag your contacts and coils from.

Let’s start converting our simple wiring diagram to the PLC program in a step by step format. I’m using the Siemens TIA Portal as the PLC Programming software.

1. Just like on the diagram, we start with the stop push-button. It will be represented with an examine OFF bit. These look like a normally closed (NC) contact.

Drag it to the first ladder rung and the program will place it to the far left. This will be a “Stop push button”.

2. Next, drag an examine ON bit and drop it to the right of the first bit. This looks like normally open contact (NO) and will be the “Start push button”.

3. From there you need to drag an output coil to the right of the other bits. It looks like a set of parenthesis. This is the “Motor Starter Coil”.

4. Most PLC programs will not allow an input to the right of the output bit. So we will add the Normally close overload contact from the print to the left side of the coil.

5. The last thing to add is the auxiliary holding contact. To do this, we need to add a branch around the start push button examine ON bit. Then, drag another examine ON bit to that branch. This will be the “Auxiliary Holding Contact”.

Your program should now look like the wiring diagram.

Let’s keep in mind that we will still need to address each bit that we have added to the program to make the program work physically.

This simply means that we have to match the program to the physical location on the input and output locations of the PLC where the push buttons and motor starter were wired. This will be covered in another article very soon.

Wrap-up

Let’s look back at what we have learned.

To program a simple motor start-stop circuit, we need to read the electrical diagram from left to right and use our toolbox on the programming software.

You will be using the most common bits in the examine ON, which will represent a normally open contact, examine OFF, which will represent a normally closed contact, and output coil or output energize.

Again, the language is sometimes different between manufacturers, but the symbols pretty well look the same. You will also need to use a branch around one bit. This is basically a parallel circuit called OR logic.

The start push button will energize the circuit and the auxiliary contact will keep it energized.

I hope this article has been helpful in the transition from wiring diagrams to PLC programming. This was a very basic program that can run a motor.

Thanks again for reading. Check back soon for more RealPars articles, leave your questions and comments and we’ll chat with you soon!

The RealPars Team

WHAT IS THE DIFFERENCE BETWEEN SCADA AND HMI?

2019-08-20T17:20:00.001+05:30

Today, you will learn the difference between SCADA and HMI. We will talk about the differences as well as the similarities, and also when each is used. There is usually some confusion because of the similarities.

So let’s dive in to SCADA for now. SCADA stands for “Supervisory Control and Data Acquisition.”
These are used for monitoring and controlling large areas, typically a full site or plant. SCADA systems are a combination of many systems including sensors, RTUs or Remote Terminal Units, and PLCs.

Data from all of these systems is then sent to the central SCADA unit. That SCADA unit has its own HMI. This is why a lot of people get confused and think SCADA and HMI are one and the same.

That HMI or “Human Machine Interface” unit on the SCADA can monitor and control anything that is connected to it. In conclusion, HMI can be part of SCADA but SCADA cannot be part of a HMI. It’s that simple.

So let’s talk about a common use for SCADA that I have personally encountered. While working for a water and wastewater treatment facility I encountered a SCADA system. The HMI was located at the main water plant building. This HMI was connected to the main SCADA unit at the water plant.

Each booster pump station within the water district was represented on the screen.

At each location there was a PLC that was connected to some sensors to monitor water flow, pressure, and other things, and it was able to run and control the pump itself.

The remote SCADA unit was connected to the PLC system and allowed operators to control and monitor each pump station from the main plant. I’m sure you can imagine how much time and labor a good SCADA system can save a company.

I like to think of a SCADA system kind of like a modern vehicle. You have several different sensors connected to different computers on board. Most of your interior features like motorized seats, climate control and other things are controlled by a BCM or body control module.

Most of your engine functions and sensors are monitored and controlled by your ECM or engine control module.

These modules all send information to a main screen in your dash for you to see and control through driver controls which is essentially your HMI.

An HMI is essentially a user control station, usually in the form of a touchscreen or a screen with some buttons attached. They are typically tied to a machine or process.

Most HMI applications have the screen tied to a PLC that it is compatible with. Certain functions and sensors can be programmed to monitor and control on the screen itself. Be sure to check out our RealPars blog post on HMIs.

So what did we learn today? Hopefully you now know the difference between a SCADA and HMI. They are different but can be used together to create a very functional and useful industrial tool. A SCADA system is comprised of remote systems all tied together at one central hub.

Our example was the water treatment pumps that were located all over a water district. They were able to be controlled and monitored from a central location at the water plant. An HMI is an interface for humans to monitor and control a machine.

Even our SCADA systems will typically involve an HMI. HMIs are usually connected to one machine or process and are able to monitor and control certain functions of that machine or process.

I hope this video has helped you. Make sure to check back later for more awesome videos!

Thank you, as always, for reading, watching and diving into the discussion with kindness and passion.

With so much love and excitement,

The RealPars Team

WHAT IS SCADA?

2019-08-20T17:18:00.002+05:30

The SCADA acronym stands for Supervisory Control and Data Acquisition.
When considering this term, you can conjure varying images and you should.

A SCADA system is a collection of both software and hardware components that allow supervision and control of plants, both locally and remotely.

The SCADA also examines, collects, and processes data in real time.

Human Machine Interface (HMI) software facilitates interaction with field devices such as pumps, valves, motors, sensors, etc.

Also within the SCADA software is the ability to log data for historical purposes.

The structural design of a standard SCADA system starts with Remote Terminal Units (RTUs) and/or Programmable Logic Controllers (PLCs).

As you know, RTUs and PLCs are microprocessors that communicate and interact with field devices such as valves, pumps, and HMIs.

That communication data is routed from the processors to the SCADA computers, where the software interprets and displays the data allowing for operators to analyze and react to system events.

Before SCADA, plant personnel had to monitor and control industrial processes via selector switches, push buttons, and dials for analog signals.

This meant that plants had to maintain personnel on site, during production, in order to control the processes.

As manufacturing grew and sites became more remote in nature, relays and timers were used to assist in the supervision and control of processes. With these devices employed, fewer plant personnel were required to be on site in order to oversee and control operations.

While relays and timers did provide some level of automation, the panels required for these devices took up valuable real estate, troubleshooting was a nightmare, and reconfiguring was difficult at best.

These issues, in conjunction with the need to grow even larger industrial plants, helped to facilitate the birth of automation.

SCADA Historical Review

– The 1950s

As you may know from the previous articles, controlling industrial plants via processors became a reality in the 1950s.
Gas and oil, utilities, and manufacturing were major users of these new technologies and supervisory control.

– The 1960s

About a decade later, telemetry came on the scene to offer even more remote capabilities with automated communication and data transmission to remote monitoring locations.

– The 1970s

Another decade later the term SCADA was used to describe systems with PLCs and microprocessors that were being used for the monitoring and control of automated processes on an even greater scale than ever before. SCADA, back then, was anything but practical.

They were colossal machines, mainframes really, and since networking was not yet in the picture, they were stand-alone units.

– The 1990s

In the next couple of decades, the ’80s and 90s, with computer systems getting smaller, the advent of Local Area Networking (LAN), and HMI software, SCADA systems were able to connect to related systems.

Unfortunately, though, the communications were typically proprietary which meant that connections outside of the particular vendor of the SCADA system were not allowed.

This early SCADA was coined “distributed SCADA systems”.

– The 1990s and 2000s

Later in the ’90s and 2000s, SCADA began to implement open system architectures with communication protocols that were not vendor specific.

As you can imagine, this opened up SCADA’s ability to connect with varying vendors. This newer, more improved SCADA was then called a networked SCADA system.

Newer and improved SCADA, unfortunately, didn’t last long.

With computer technology growing rapidly, IT development quickly gathered steam.
The default database for IT became Structured Query Language (SQL) databases.

SCADA developers didn’t implement these standard databases so SCADA became out of date rather quickly when other technologies so rapidly changed.

Today

Current day SCADA systems have adapted to the changing technologies and have a great advantage over the older SCADA systems.

With the adoption of modern IT standards such as SQL and web-based applications, today’s SCADA allows for real-time plant information to be accessed from anywhere around the world.

Having this data at the operator’s fingertips facilitates improved plant operations allowing for responses to SCADA system queues based on field collected data and system analysis.

These operator interactions can be from a computer right on the plant floor to an office building in some other region in the world.

Advancing technologies have indeed made the world seem like a very small place, relatively speaking. And because the current SCADA system software has typically adopted the SQL database model, historical collection of data may be logged and used in trending applications to further improve plant processes as well as creating mandated record keeping for some of the industries out there.

Essentially, SCADA is a collection of hardware and software components. This collection of components begins with real-time data collected from plant floor devices such as pumps, valves, and transmitters.

These components don’t have to be from a particular vendor, they just need to have a communication protocol that the processor can utilize.

Data collected from the field devices is then passed to the processors such as PLCs.
From the processor, the data is distributed to a system of networked devices.
These devices may be HMIs, end-user computers, and servers.

On the HMI and end-user computer, graphical representations of the operations exist for operator interactions such as running pumps and opening valves.
This data may also be analyzed and used to enhance plant production and troubleshoot problems.

Thank you so much for reading, watching and adding your voice to this automation conversation.

Got a friend, client, or colleague who could use some of this information? Please share this article.

The RealPars Team

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2019-08-16T23:45:00.000+05:30

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WHAT IS SENSOR CALIBRATION AND WHY IS IT IMPORTANT?

2019-08-16T22:34:00.004+05:30

When engineers design modern process plants, they specify sensors to measure important process variables, such as flow, level, pressure, and temperature.

These measurements are used to help the process control system adjust the valves, pumps and other actuators in the plant to maintain the proper values of these quantities and to ensure safe operation.

So how does a plant maintain the operation of these sensors to guarantee that the actual value of the process is sensed and passed to the control system?

In this article, you will learn that the answer to that question is: “Sensor Calibration”.

Sensor calibration is an adjustment or set of adjustments performed on a sensor or instrument to make that instrument function as accurately, or error free, as possible.

1. Errors in Sensor Measurement

Error is simply the algebraic difference between the indication and the actual value of the measured variable. Errors in sensor measurement can be caused by many factors.

1.1. Error due to Improper Zero Reference

First, the instrument may not have a proper zero reference.

Modern sensors and transmitters are electronic devices, and the reference voltage, or signal, may drift over time due to temperature, pressure, or change in ambient conditions.

1.2. Error due to Shift in Sensor’s Range

Second, the “sensor’s range” may shift due the same conditions just noted, or perhaps the operating range of the process has changed.

For example, a process may currently operate in the range of 0 to 200 pounds per square inch (PSI), but changes in operation will require it to run in the range of 0 to 500 pounds per square inch (PSI).

1.3. Error due to Mechanical Wear or Damage

Third, error in sensor measurement may occur because of mechanical wear, or damage. Usually, this type of error will require repair or replacement of the device.

Errors are not desirable, since the control system will not have accurate data from which to make control decisions, such as adjusting the output of a control valve or setting the speed of a feed pump.

If the calibration is too far from the accurate process conditions, process safety may be jeopardized.

If I am an instrument or operations engineer in a plant, I need every instrument to have a proper calibration.

Proper calibration will yield accurate measurements, which in turn, makes good control of the process possible.

When good control is realized, then the process has the best chance of running efficiently and safely.

2. Sensor Calibration

Most modern process plants have sensor calibration programs, which require instruments to be calibrated periodically.

Calibration can take a considerable period of time, especially if the device is hard to reach or requires special tools.

2.1. What is an “As-Found” Check?

In order to minimize the amount of time that it takes to perform a sensor calibration, I would first do an “as found” check on the instrument. This is simply performing a calibration prior to making any adjustments.

If the current instrument calibration is found to be within the stated tolerance for the device, then re-calibration is not required.

2.2. How to Perfom an “As-Found” or “Five-Point” Check

To perform an “as-found” check, an accurate and precise instrument is used to develop process signals corresponding to 0%, 25%, 50%, 75% and 100% of the process range of the transmitter.

The corresponding transmitter output, in milliamps, is observed and recorded. This is called a “Five-point” check.

Then, in order to check for hysteresis, a phenomenon whereby the sensor output for a process value is different going ‘downscale’ as it is going ‘upscale’, the output signals corresponding to 100%, 75%, 50%, 25%, and 0% in order are recorded.

2.3. How to Calculate the Deviations (Errors) of a Sensor

The deviations at each check point are calculated and compared to the deviation maximum allowed for the device.

If the deviation is greater than the maximum allowed, then a full calibration is performed.

If the deviation is less than the maximum allowed, then a sensor calibration is not required.

Let’s assume that the maximum deviation tolerance is 0.5%.

Using the data from the calibration sheet, we see from the graph that the deviations are all less than the maximum deviation allowed of 0.5%.

Therefore, no additional calibration is required.

Now let’s assume that the maximum deviation tolerance is 0.20%.

Using the data from the calibration sheet, we see from the graph that some deviations are greater than the maximum deviation allowed of 0.20%.

Therefore, a sensor calibration is required.

2.4. How to Perform a Sensor Calibration

To calibrate, we need a very accurate process simulator, in this case a pressure supply, connected to the process side of the transmitter.

A current meter is attached to the output to measure the transmitter’s 4-20 milliamps output. Ideally, a National Institute for Standards and Testing-calibrated simulator and current meter are used. In practice, we can use very accurate process meters and pressure input modules.

2.4.1. Analog Sensor Calibration (Zero and Span Adjustement)

If we have an analog transmitter, we must adjust zero and span to reduce the measurement error. With an analog transmitter, there is a ZERO and SPAN adjustment on the transmitter itself.

Zero adjustment is made to move the output to exactly 4 milliamps when a 0% process measurement is applied to the transmitter, and the Span adjustment is made to move the output to exactly 20 milliamps when a 100% process measurement is applied.

Unfortunately, with analog transmitters, the zero and span adjustments are interactive; that is, adjusting one moves the other. Therefore, the calibration is an iterative process to set zero and span, but only 2 to 3 iterations are usually required.

2.4.2. Digital Sensor Calibration (Sensor and Output Trim)

With a digital transmitter, we can adjust the incoming sensor signal by adjusting the Analog to Digital converter output, which is called “sensor trim”, and/or the input to the Digital to Analog converter in the output circuit, which is called “4-20mA trim” or “output trim”.

2.4.3. After Calibration

After calibration, the errors are graphed once again. As with the “as found” values, there is some degree of hysteresis. However, the maximum deviation has been reduced from 0.38% to 0.18%, well within the tolerance of 0.20%.

In this artcle, you learned the importance of sensor calibration of a measurement signal.

Calibration is an adjustment or set of adjustments performed on a sensor or instrument to make that instrument function as accurately, or error free, as possible.

Proper sensor calibration will yield accurate measurements, which in turn, makes good control of the process possible. When good control is realized, then the process has the best chance of running efficiently and safely.

Got a friend, client or colleague that might find this easy-to-follow article about sensor calibration useful? Share this article. Not only will they thank you for it, but you’ll have one more person to add to your fraud squad.

Happy learning,

The RealPars Team

WHAT IS OSI MODEL?

2019-08-16T22:32:00.002+05:30

OSI stands for Open Systems Interconnection and is a conceptual framework for how applications communicate over a network.

There are seven layers within the model and the layers depiction is used to help users identify what is happening within a networking system.

Introduction to OSI Model

The OSI model layers are typically described from the top layer down.

The layers are described as Application, Presentation, Session, Transport, Network, Data Link, and Physical.

These layers are provided by a mixture of network card drivers, operating systems, applications, and networking hardware that facilitate the transmission of signals over Ethernet, Fiber Optic, Wi-Fi, or other wireless protocols.

7. Application Layer

We’ll describe the layers from the top down as the top layer is the Application layer or layer 7. This is the layer that most users interact with and will recognize.

The Application layer provides network services to the end user. These services are protocols that work with the data the client is using. One of these protocols may be HTTP that is used with web browsers such as Google Chrome, Firefox, and Internet Explorer.

Other examples of applications that use this layer are Office, Outlook, and Skype.

All of those interactive applications provide a set of services that allow the application layer to supply data to and receive data from the Presentation layer.

6. Presentation Layer

The Presentation layer, or layer 6, performs the uncomplicated task of syntax processing or converting data from one format to another.

For example, say you are ordering something from an online store. These transactions are typically handled in a secure transmission which means that the data passing between the “store” or the Website Application will transmit encrypted data to the Presentation layer that will need to be decrypted and processed.

This layer handles translating the data from the top layer, which is presented in application format, to network format and vice versa.

After the Presentation layer processes the data from one format to another, the information is then passed to the Session layer or the Application layer depending on whether the data is transmitting or receiving.

5. Session Layer

At the Session layer, or layer 5, the construction, direction, and conclusion of connections between devices occur. This layer supports multiple types of connections as well as being responsible for authentication and reconnection if a network interruption should occur.

After the session is established the data then passes to or from the Transport layer.

4. Transport Layer

The Transport layer, or layer 4, is responsible for the transmission of data across network connections. This layer coordinates how much data to send, how fast, where it goes, and these sort of things.

Of the most widely known protocols for internet applications, these services may be provided by “Transmission Control Protocol” or TCP and “User Datagram Protocol” or UDP. Other protocols may provide additional capabilities including error recovery, data flow, and retransmission.

Once the Transport layer has completed its function, the data is then passed to or from the Network layer.

3. Network Layer

The Network layer, or layer 3, handles the routing of data.

After the data arrives at this layer, each frame of data is examined to conclude if the data has reached its ultimate target. The layer sends data to the correct destination on outgoing transmissions and receives incoming transmissions as well. The IP portion of TCP/IP is the commonly known network layer for the Internet.

This layer also manages the mapping between logical addresses and physical addresses, for IP addresses, this is accomplished through Address Resolution Protocol or ARP.

The data is then passed to the next required layer which is the Data Link layer.

2. Data Link Layer

The Data Link layer, or layer 2, is considered the most complex of the layers. This layer is often divided into sublayers called Media Access Control or MAC and Logical Link Control or LLC.

The layer sets up links across the physical network. When this layer received data from the Physical layer, it checks for transmission errors and then packages the bits into data frames. From there, this layer manages the physical addressing methods for the MAC or LLC layers. An example of the MAC layer includes 802.11 wireless specifications as well as Ethernet.

At the Data Link layer, the data passes to or from the final layer in the OSI model which is the Physical layer.

1. Physical Layer

The Physical layer, or layer 1, is the electrical/physical layer of the model. This layer encompasses the network cables, power plugs, cable pinouts, wireless radio frequencies, connectors, transceivers, receivers, repeaters, pulses of light, electric voltages, etc.

When troubleshooting problems, this is typically the first place to start. Is the device plugged in? Is the wireless card working?

At this layer, the model transmits the digital data bits from the source or sending devices Physical layer, over network communications media, which can be electrical, mechanical, or radio, to the receiving or destination devices Physical layer.

The OSI model is a guide for developers and vendors to smooth the progress of developing communication products and software programs that will work in cooperation with a commonly established model.

Once you understand the model, you can then understand which protocols and devices will be compatible with one another.

Thank you so much for reading, watching and adding your voice to this automation conversation.

Your thoughtfulness and energy make this one of the most supportive and encouraging communities in the world!

The RealPars Team

WHAT IS A VFD?

2019-08-13T15:38:00.000+05:30

Today you will learn about VFD. Specifically, what it is and when do we use it with automation and PLCs.

So what exactly is a VFD? Well, it stands for Variable Frequency Drive.

They are used for running an AC motor at variable speeds or let them ramp up their speed to give them a smooth startup.

Some people simply call them drives.

VFDs work by adjusting the frequency of the motor to adjust the rpms.

To do this, a VFD will actually convert the voltage twice:

1) First, it converts our three-phase AC to DC. This is accomplished with diodes.

2) Then it cleans the DC with a capacitor.

3) Next, it will convert the DC to AC. This is accomplished with transistors acting as switches.

Utilizing these “switches” is what allows the VFD to adjust the frequency that the VFD supplies to the motor. This, in turn, controls the speed of the motor.

Now I know this is a lot of information to take in. Let me compare the internal workings of the VFD with a simple plumbing system.

First, let’s look at the diodes that convert the AC to DC. This operates like a check valve in a water system.

A check valve, like a diode with electricity, only allows water to flow in one direction.

The capacitor acts as a water filter to keep everything clean and useable.

The transistors act like valves. They turn the flow on and off when needed. This allows the VFD to adjust the frequency to the motor.

Now that we have an understanding of how a VFD works, let’s see what they are used for.

One very common use in industry is to control the speed of a water pump in a water treatment facility.

A water treatment plant typically has a constant flow of water coming in to the plant. However, if the water demand exiting the plant is lower than the supply entering the plant, then the operator will need to slow down the supply.This is achieved by using a VFD on the AC motor.

The operator can monitor water flow and manually adjust the VFD accordingly.

Another great thing about VFDs is the fact that they can be controlled with a PLC. Using basic communication protocols that have been covered in previous videos, such as RS232 and RS485, PLCs can monitor and control motor speeds using the VFD.

This helps make a process like water treatment that much easier and more efficient. This setup can be used in any situation that would benefit from automation.

Let’s look back at what we now know. VFD stands for Variable Frequency Drive. They are used for controlling the speed of an AC motor.

They are also used for ramping up a motor for a smooth startup, or to prevent a heavy load from straining the motor on startup.

This is accomplished by adjusting the frequency delivered to the motor. A setup of an AC to DC converter, then DC to AC converter.

VFDs are used throughout industry. A common example is to regulate water flow entering a water treatment plant. VFDs allow the operator to control the flow of the pump manually or automatically with a PLC.

There are many different brands and features available. If you are looking at using a VFD just be sure to do your research!

I hope this blog post has helped you get a feel for VFDs. They really can make any automation or industrial process operate more smoothly.

As always, be sure to check back soon for more RealPars videos and blog posts!

Thanks for reading and sharing our blog posts with your friends and colleagues.

The RealPars Team

WHAT IS A LEVEL SENSOR?

2019-08-13T15:27:00.002+05:30

When you get in your car to go on a drive you often look at your gas gauge, which is a type of a level sensor. Industries use several different types of level sensors to detect their products.

In this article, we are going to talk about the different types of level sensors used in the industry, in a very easy-to-follow format.

Level Sensor Classification

Level Sensors can be broken into two classifications;

– Point level measurement

– Continuous level measurement

Point level measurement indicates when a product is present at a certain point and continuous level measuring indicates the continuous level of a product as it rises and falls.

The sensors for point level indication are:

– Capacitance

– Optical

– Conductivity

– Vibrating (Tuning fork)

– Float Switch

The sensors for continuous level measuring are:

– Ultrasonic

– Radar (Microwave)

We will talk about how they work and which applications are best suited for their technology, as well as their limitations in certain applications.

Point Level Measurement Sensors

Let’s talk about point level indication sensors first. Starting with capacitance level sensors.

1. Capacitance Level Sensor

Let’s talk about point level indication sensors first. Starting with capacitance level sensors.

A capacitance level sensor is a proximity sensor that gives off an electrical field and detects a level by the effect on its electrical field. These sensors are:

– Small

– Less expensive than other sensors

– Invasive to the product

– Accurate

– Have no moving parts

However, they do have to be calibrated and will only detect certain liquids.

Capacitance sensors can be used in liquid storage tanks. A water treatment facility that has storage tanks would be an ideal use for a capacitance sensor.

2. Optical Level Sensor

The next point level sensor we will talk about is an optical level sensor.

Optical sensors work by converting light rays into electrical signals which measure a physical quantity of light then translate it into a measurement.

– These sensors have no moving parts

– They are not affected by high pressure or temperature

– They are small in size

– They can be used in liquid applications

However, if the lens gets coated or dirty they would require cleaning.

They can be used as low-level indicators to prevent run dry conditions when using oil, coolant, or hydraulics.

3. Conductivity (Resistance) Level Sensor

Another style of point level sensor is conductivity or resistance.

A conductivity or resistance sensor uses a probe to read conductivity. The probe has a pair of electrodes and applies alternating current to them.

When a liquid covers the probe its electrodes form a part on an electric circuit, causing current to flow which signals a high or low level.

The advantages of using a conductivity level sensor are:

– There are no moving parts

– They are low cost

– Fairly easy to use

The disadvantages are:

– They are invasive (meaning they must touch the product being sensed)

– They only sense conductive liquids

– The probe will erode over time

Appropriate use for these sensors would be for signaling high or low levels.

4. Vibrating (Tuning Fork) Level Sensor

Vibrating or tuning forks is another type of point level sensor.

They use a fork-shaped sensing element with two tines. The fork vibrates at its natural resonant frequency. As the level changes, the frequency of the fork will change detecting the level. These sensors are:

– Cost effective and compact

– Invasive to the product, meaning they have to touch the material to sense the level

– Easy to install

– Essentially maintenance-free

They have unlimited uses based on the material that they can sense. Mining, food and beverage, and chemical processing industries use these sensors for their applications.

5. Float Switch

The last point level sensor that we will talk about is a float switch.

Float switches use a float, a device that will raise or lower when a product is applied or removed, which will open or close a circuit as the level raises or lowers moving the float.

The advantages of a float switch are:

– They are non powered device

– They provide a direct indication

– They are inexpensive

The disadvantages are:

– They are invasive to the product

– They have moving parts

– They can be large in size

Float switches will only give an indication for a high or low level, they cannot measure a variable level. A great use for float switches is in liquid storage tanks for high or low-level indication.

Continuous Level Measurement Sensors

Now, let’s talk about continuous level measurement sensors. We will start with ultrasonic sensors.

1. Ultrasonic Level Sensor

Ultrasonic level sensors work by emitting and receiving ultrasonic waves. The time it takes for the waves to reflect back is how distance is measured.

The advantage of using this type of sensor is that:

– These sensors have no moving parts

– They are compact

– They are reliable

– Non-invasive (Non-contact)

– Unaffected by the properties of the material they are sensing

– Self-cleaning because of the vibrations they give off

The disadvantage of using this type of sensor is that:

– They can be expensive

– In some situations, the environment can have a negative effect on them

An example application is a hot asphalt tank in a shingle manufacturing plant.

The ultrasonic sensor would be placed in the top of the tank away from the hot asphalt and used to sense the level in order to send a fill request for the tank.

2. Radar Level Sensor

Radar or microwave is also a continuous level sensor.

These sensors transmit microwaves by an antenna on the radar sensor. The product that is being sensed reflects these microwaves back to the antenna and the time from emission to reception of the signal is proportional to the level of the product.

The advantages of radar sensors are that:

– They are not affected by temperature, pressure or dust

– They can also measure liquids, pastes, powders, and solids

– They are very accurate and require no calibration

– They are non-invasive because they do not have to touch the product that it is sensing

The disadvantages of radar sensors are that:

– They are expensive

– They have a limited detection range

If we go back to our shingle manufacturing plant example a Radar level sensor could be an ideal solution. Much like the ultrasonic sensor, radar sensors are ideal for hot liquid storage tanks.

Summary

Let’s wrap up and review what we talked about today.

We talked about seven different types of level switches and their applications.

Some of their applications can overlap and when deciding on a sensor it is important to identify the product that you are sensing and the type of feedback that your application requires.

Sensors like conductivity or resistance, capacitance, Tuning Fork, float switches, and optical level sensors can be used to indicate a high or low level. While ultrasonic and radar level sensors can measure your level to give specific feedback to how much of product is in a tank.

Thank you so much for reading, watching and adding your voice to this automation conversation.

Got a friend, client, or colleague who could use some of this information? Please share this article.

The RealPars Team

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