Weights come in all shapes and sizes, and materials, and classes…well you get the idea. Choosing the right weight for your application shouldn’t be guesswork.

Troemner has developed a tool with just this in mind. Troemner’s Weight Selector is designed to guide you through the process of choosing the correct weight for your application. Simply select the parameters that best match your needs, based on a series of questions, and our Weight Selector will automatically calculate your optimum weight choice.

We developed this tool for you, so please, utilize this as many times as you would like. Click here to get started!

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Is one of the missing links to your day to day activities the inability to actually get someone to respond to your queries?  Are you looking to get answers to your technical questions? When sourcing a calibration service provider do you look for one who is accredited? Do you need a storage case or  heavy duty case that will protect your asset when sending them into Troemner for recalibration?  If you answered yes to any of these questions keep reading.

My name is Will B. Precise and I would be glad to answer any of your questions. I’m available whenever you are, at your convenience. Look to me for help when you need it.  I will respond in a timely manner.  Follow me on twitter to hear daily tweets of how I can help you with your laboratory needs as well as the occasional tidbit of technical information.  Look for me on our web site to get answers to your FAQ’s and be sure to check in weekly for my latest blog. Trust Troemner and I promise Will B. Precise every time!

Look for me at www.troemner.com.

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So, you’ve purchased Troemner Precision Weights.  Now you may be asking yourself:  ”How do we take care of them until we send them back to Troemner for recalibration?”  We’re glad you asked…

Handling:

Precision weights are sensitive and we should take extra care when handling them. We recommend using lint free gloves at all times when handling the weights. Of course there are other options available. We have a variety of accessories designed with your precision weights in mind. Accessories include weight forks, lifters, and tweezers which will assure you get the best out of your precision weights.

Cleaning:

It is often said that no weight cleaning method is perfect but here are a few daily techniques you can use to keep your weights contaminant free.

Before each use, clean all weights with a camel hair or other suitable soft brush to remove any particles that might have settled on your weights.  If you notice a spot of debris while brushing your weights, try using a lint free cloth to gently rub it out.  Remember to pay special attention to the bottom surface, since this area tends to be overlooked.

If the weights still have debris after using the daily/periodic-cleaning methods above try the following:  Use cheesecloth dampened with ethyl alcohol and gently rub the weights surface in order to remove any residual or stubborn debris.  If alcohol does not remove the foreign debris, repeat the process using other solvents such as window cleaner or distilled water.  If solvents other than distilled water and alcohol are used, the weights should be cleaned again using alcohol to remove any residual solvent from the weights.

For brass, cast iron, sheet metal or aluminum weights only use distilled water – alcohol or other solvents can deteriorate coated surfaces and aluminum.

After spot cleaning, the weight should not be used for a period of at least 4 hours in order for the weight to return to thermal equilibrium with the environment.

They’re clean, now what do I do?  Weight Storage the Troemner Way

Troemner’s polycarbonate cases are not unlike the cases for fine timepieces. The cases are constructed completely of high quality polycarbonate and designed specific to the style and size of the weights. All cases have locking lids and custom bumpers to assure the weights are held securely inside the case.

Individual cases are available for weights from 1mg through 2kg. Weight Set Cases are available for sets where the largest weight is 500g and below. The weight cases can be used to store your weights in or outside of your lab.

We also have a full line of specialty cases and custom weight carts designed for all of your weight storage and shipping needs.

For more information about Troemner Weights, Calibration Services and Accreditions visit our website at  www.troemner.com.

To view our full line of  weight cases and accessories, visit  Troemner Weight Cases.

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Troemner’s Pipette Calibration Laboratory was the first NVLAP* accredited laboratory for pipettes in the United States. We have invested in the most advanced instrumentation including gravimetric and spectrophotometric equipment for calibrations of pipettes. Gravimetric pipette calibrations are performed using six high precision balances and mass comparators; some with resolution as low as 1 µg. Troemner also uses humidity traps and other methods to assure accurate gravimetric calibrations. Due to the direct relationship between weight and volume, the Troemner reputation for weighing accuracy is fully utilized in the pipette calibration process to achieve low measurement uncertainties. Spectrophotometric calibrations are performed using photospectrometry, whereby refractive index is proportional to volume. Both techniques assure that only the highest standards are met for complete reliability of pipette calibrations

Pipette Calibration Services Include:

• Calibration of pipettes, repeaters and burettes
• Traceability to NIST
• NVLAP Accredited – 0.1 µl to 10 ml, Laboratory capability 0.1 µl to 100 ml
• Low measurement uncertainty: ±0.027 µl to ±5.98 µl
• Every channel of a multi-channel pipette is fully tested and calibrated
• Thorough evaluation of pipette performance
• Visual vacuum leak test
• Full service and parts availability for all types and brands of pipettes
• Free repair estimates
• Gravimetric and spectrophotometric calibration procedures
• Fast turnaround time

Troemner offers three standard pipette calibration services. We can also customize calibrations to meet your particular requirements.

Click here to view complete details on Troemner’s Pipette Services

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Maintaining Control Standard Weights

The blog “Why Use Weights” covered the reason for traceability and proving quality of the laboratory.  This article is more detailed on the effects of not having a quality process in place to determine the weight of substances.

It is unlawful for any person, knowingly or purposely, to obtain or to possess a controlled substance, unless the substance was obtained by a valid prescription. This article will address the opposition facing the State’s prosecutors in proving beyond a reasonable doubt the weight of an illegal substance.  Since drug trafficking laws vary from state to state, the facts used in creating this article may not apply to every state.  However, a constant exist in that it is the obligation of the state forensic laboratories to assist the state in proving the correct weight of the substance.  It is the forensic verification that will ultimately determine whether the accused will stand trial in Superior Court or Municipal Court.

Degrees of crime in a narcotics case are distinguished by the weight of the illegal substance in question.  Sentencing can range from a hefty jail term to a one year probationary period, both typically accompanied by a fine.  Because weight determines the degree and the degree ultimately determines the sentence, weighing standards are quick to be attached by defendants’ legal counsel.

It has often become the immediate strategy of the defense lawyers to question the accuracy of the balance, placing the burden of proof of that accuracy on the forensic laboratory.  It becomes 2 the responsibility of the forensic scientist to provide the confidence in the process needed to erase any doubt as to the true weight of the substance.

Let us examine this by way of example.  The case is possession of 5g or more of hashish in the State of New Jersey and the defense lawyer is trying to have the case heard in Municipal Court by proving the amount measured is less then 5g. The forensic laboratory has determined that the weight is 5.0020g ±0.0014g.  The defense lawyer in an effort to get the case heard in a lower court will investigate the process for determining the weight, hoping for reasonable doubt that will persuade the prosecutor to reduce the offense to 5g or less and enter the case into Municipal Court.

The defense lawyer will place the “weight” of the case on the responses provided by the forensic scientist to the following questions.

How is the weight of the substance determined?

The substance is placed on a 200g 4 place balance with a digital readout.  The sample in question has a weight of 5.0020g ±0.0014g.  The value ±0.0014g is the error in the process.  This error is caused by the error of the balance and of the control standard. The substance is over the limit for Municipal Court even with the accountability for the probability of error.  This result will of course disappoint the lawyer.  The lawyer must now investigate further to determine if the balance measurement error is in error and the results not sufficient to send his client to Superior Court.

How do you determine the balance is correct?

The balance used to determine the weight of the substance is located on a solid base that is not affected by area vibrations, heating and cooling system and away from direct light.  The temperature and humidity are controlled to not vary by more then 2ºC or 10% RH during the test.  The balance is serviced and calibrated yearly by a certified vendor that has met the laboratory’s internal quality standards.  The balance is checked to determine the errors in the balance caused by repeatability, linearity and corner loading effects. Repeatability determines the balance ability to indicate the same value for the same weight.  Linearity test for error caused by different nominal values being weighed, such as placing a 5g control standard and then a substance that is estimated to be 5g.  Corner loading is the error caused by not centering the substance being weighed on the weighing pan. The accumulative error caused by these effects has been determined to be ± 0.0005g.  The balance is verified between calibrations by using a control 3 standard weight that is equal to the estimated weight of the substance to be weighed prior to using the balance.

How do you determine that the control standard is correct?

The control standard is calibrated yearly by an accredited laboratory meeting the

guidelines of ISO 17025 and the internal quality standards of the forensic laboratory.  The as found data is compared to the previous calibration data and the data collected prior to placing a weight into service.

The process for placing the weight in service is to perform 10 weighings.  The average of the weighing is now the expected value of the weight in our laboratory environment.  Every time the weight is used to verify the balance the value indicated on the balance is compared to the average and must be within the control limits set by the internal quality standards.  The value is entered into a spreadsheet that will provide an indication of the weight value and balance operation over time.  The spreadsheet and the calibration data are used to determine if the new calibration is correct and determine the calibration interval of the control standard.  The spreadsheet for the 5g weight indicates a variation of 0.0005g. There is an error associated with the process of 0.0005 for both processes.  How is this error combined to get a final error of 0.0014?

The confidence the forensic scientist has in the process has been determined statistically.

The variation in the test performed using the balance and control weight has induced a possible error of 0.0005g.  Since both tests are independent, the values are squared then summed and the square root determined.  The root sum square value is multiplied by 2 which provide the test a confidence interval of 95% and the total uncertainty of 0.0014g. The final weight of the substance is 5.0020g ±0.0014g.

Can the test repeat no matter who uses the balance?

Yes; if handled in accordance with internal procedures for handling and process evidence

is followed.  It is the policy of the lab that all forensic scientists handle the control standards with plastic or fiber tweezers, or lint free gloves.  If the weight appears dirty then the weight is compared to values in the spreadsheet to determine if the weight has changed.  If the weight changes then the weight is cleaned gently with a lint free cloth.  After cleaning the weight, it is compared again to previous readings in the spreadsheet to determine if the weight has changed in value.  If the weight has changed in value, outside the limits set by the laboratory then the weight is removed from service and sent for calibration. 4

The lawyer has completed the questioning of the forensic scientist and draws the following conclusions.  The laboratory has a process to maintain the balance and control standard used to determine the weight of the substance, and has evidence of traceability and control of the substance.  Faced with the process being proven tried and true, the lawyer in our example now lacks reasonable doubt.  The burden now “weighs” on the lawyer to present his case in Superior Court.

Absolutely.  Positively.  Precise.