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Buying a Calibrator – How Accurate Does It Need to be?

Buying a Calibrator – How Accurate Does It Need to be?

When deciding on a calibrator to purchase for your lab, the number one question we hear is how accurate my calibrator needs to be? This is especially true as the more precise the calibrator, the more expensive it can be. This factors into the difficulties in choosing the right choice within your budget.

Here is a guide that will give details on accuracy and standard terms used so that you can make the best choice for your lab.


Test Accuracy Ratio Definition

Test Accuracy Ratio (TAR) is the accuracy of the calibrator compared to the accuracy of the device being calibrated.


Test Uncertainty Ratio Definition

Test Uncertainty Ratio (TUR) compares the uncertainty of the device under test (DUT) to the fate of the measurement process. It is the ratio of the accuracy tolerance of the unit under calibration to the uncertainty of the calibration standard used.


Industry Norms Over the Years

For many years, a TAR of 10:1 was the industry norm. Technology changed, and the test equipment and DUTs became increasingly accurate, even lower-priced ones. Because of that, TARs of 4:1 became the new acceptable standard.

The concern is that the closer inaccuracy the DUT is to the calibrator, the highest possibility of false acceptance and false rejects. False accepts are a more significant concern as they can cause a traceability chain of false takes. This can lead to inferior products being manufactured in critical industries and fatal results. At the base of this problem is uncertainty. Suppose a measurement is close to being out of tolerance. In that case, the tension in the calibration process might be enough to cause false accept or reject conditions.


One Possible Solution

Guard-banding is a technique to protect against incorrect conformity decisions caused by measurement uncertainty or entity dispersion.

The region of permissible values of the entity’s quality characteristic is reduced proportionately to the actual measurement uncertainty or dispersion.

It is a technique that looks at how significant the calibration process uncertainty is and determines the likelihood that it could cause a false acceptance.

Guard-banding calculates a tolerance window for the measurement to avoid these lousy concept situations.

The guard-banding calculation can assist you in following the 4:1 TUR rule recommended. It also helps determine the desired calibrator accuracy needed to perform calibrations on your device under test.


Work With an Accredited Laboratory Provider

At SRP control systems ltd, we work closely with leading manufacturers to provide our customers with the best products and services. If you are still determining the best calibrator to fit your needs and budget, we can help. With over 40 years in the industry, we have various calibrators that fit multiple industries ’ needs. As an ISO 9001:2015 registered company with a state-of-the-art ISO 17025:2017 accredited laboratory, we understand the equipment.

Contact us to discuss your needs for purchasing a calibrator.

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