What can happen when we use an accuracy specification and assume all the measurements are centered in relation to the specification limits? It is a typical problem in the metrology community, where many papers assume a centered process or Measurement. When the Measurement deviates from the true value, it is said to have a bias […]
How Do I Calculate TUR? How to 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, […]
TAR versus TUR: Why TAR should RIP ASAP In our last blog, Examining the History of TAR and TUR, we examined several outdated, and to some extent wrong, practices, such as Test Accuracy Ratios (TARs) and requesting NIST traceable calibrations. Remember when they buried the word "DEF"? Maybe we, as metrologists, need to do that […]
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 […]
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 […]
Guide for Understanding Uncertainties on a Morehouse ASTM E74 Calibration Certificate Reporting the Expanded Uncertainty on an ASTM E74 Calibration Certificate 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 […]
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 […]
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 in the metrology community. We are hoping to simplify […]
The Importance of Considering Reproducibility in the Measurement Process Uncertainty - Intro 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). […]
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 […]
Load Cell Stability – How It Can Kill Your Uncertainty Budget Load cells are a combination of metal, strain gauges, adhesive, and more. Like humans, every measuring instrument is subject to aging. Load cells age from mechanical stress or fatigue, and over time this ensures that there will be some instability in the system. Some […]
Cosine Error Should be Considered in any Torque Measurement Process ISO/IEC 17025 When Calculating Torque Measurement Error Cosine Error should be considered A ‘vector’ is known as a quantity that is defined by its size and direction. Every time the effect of a known force is evaluated on a static or dynamic system, all applied, […]
