Category: Measurement Uncertainty

How do I Calculate TUR?

Correctly calculating Test Uncertainty Ratio (TUR) is crucial because it is a commonly accepted practice when making a statement of conformity. It helps you analyze measurement risk and is often used in decision rules. Although TUR is defined in the ANSI/NCSL Z540.3 Handbook and ILAC G8, these universal standards are not always followed. Furthermore, these […]

TAR versus TUR: Why TAR should RIP ASAP

In our last blog, Examining the History of TAR and TUR, we looked at several outdated, and to some extent wrong, practices such as Test Accuracy Ratio (TARs) and requesting NIST traceable calibrations. Remember when they buried the word "DEF"? Maybe we, as metrologists, need to do that with TAR. We will examine it in […]

Examining the History of TAR and TUR

Why examine TAR and TUR? Hasn’t each topic been covered for decades now? When we look at TAR and TUR concepts, we find that many in the metrology community have adopted TUR. Both guidance documents and standards have moved away from TAR. However, when we look at the laboratories making measurements, they are decades behind […]

Measurement Uncertainty

In the last Back-to-Basics blog, I covered Calibration versus Verification. As I continue to cover basic concepts for beginners, this blog will define measurement uncertainty and examine why it is important. What is Measurement Uncertainty? What measurement uncertainty is not is an error. It is imperative to understand the difference between these two terms as […]

Ultimate Guide for Understanding Uncertainties on a Morehouse ASTM E74 Calibration Certificate

Reporting the Expanded Uncertainty of the measurement is a requirement of ISO/IEC 17025 and likely always will be. However, if you look at several different certificates of calibration, their Expanded Uncertainty reported, contributors and reporting methods will vary greatly. Some include a blanket statement of uncertainty, while others simply ignore significant contributions required by several […]

Load cell calibration: What does “Traceable to NIST” really mean?

Load cells have various applications across several fields, from verifying the correct amount of stamping press force to testing rocket thrust stands. They are so common that almost everyone owns several in some shape or form, whether they realize it or not. Load cells are found in your car, bathroom scale, and almost any digital […]

How to Calculate the Resolution of a Load Cell

Per Section 4.14 of JCGM 200:2012, Resolution is the “smallest change in a quantity being measured that causes a perceptible change in the corresponding indication.” Over the years, this simple definition has become a topic of confusion amongst the metrology community. We are hoping to simplify how to calculate the resolution of the Unit Under […]

The Importance of Considering Reproducibility in the Measurement Process Uncertainty

Most people in the metrology community will agree that a calibration laboratory's ability to reproduce measurement results belongs in an uncertainty budget. Several Accreditation Bodies require reproducibility to be at least considered as part of a calibration laboratory's Calibration and Measurement Capability (CMC). The question on Reproducibility is, does it only apply to my equipment, […]

How to Calculate the Uncertainty of a Deadweight Primary Standard Machine

Figure 1: Morehouse 1,000 lbf automated deadweight machine Deadweight Force Machines or Primary Force Standard (CMCs as low as 0.001 % of applied force) – a deadweight force applied directly without intervening mechanisms such as levers, hydraulic multipliers, or the like, whose mass has been determined by comparison with reference standards traceable to the International […]
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