Key Takeaways: Moist Air Density Importance: Essential for buoyancy corrections in mass calibration; air density determines the upward force acting on weights and standards. Core Formula: Typically calculated using the CIPM-2007 formula (or the simplified approximation) to determine the density of ambient air. Required Variables: You must accurately measure three ambient conditions: Air Temperature, Barometric […]
Key Takeaways: Test Uncertainty Ratio (TUR) Definition: The variation in measurements of the same measurand under *changed* conditions (e.g., different operators, different days, or different equipment). Definition: The ratio of the span of the tolerance of a measurement quantity to the expanded uncertainty of the measurement system. The 4:1 Rule: Historically, a TUR of 4:1 […]
Introduction Emissivity is a source of uncertainty that affects IR temperature (i.e. radiation thermometry). It should be included in uncertainty budgets for blackbody calibrators and IR Thermometers. However, many ISO/IEC 17025 accredited laboratories have not included emissivity uncertainty in their budgets because their lab personnel did not know how to evaluate it. Furthermore, […]
Key Takeaways: Local Gravity Calculations The Problem: Gravity varies by latitude and altitude; using standard gravity (9.80665 m/s2) can lead to significant measurement errors. Impact on Mass/Force: Essential for deadweight testers, force transducers, and high-precision weighing where local acceleration is a variable. Calculation Methods: Can be determined via local geological surveys (most accurate) or mathematical […]
Introduction Did you know that air buoyancy is a significant contributor to uncertainty in measurement results? It affects the results of many tests and calibrations if you do not apply air buoyancy correction. Especially, measurements where a weight is involved, such as mass, force, pressure, and torque. Many labs are not taking this […]
Each month, I write one or two articles and post them on my blog. My goal is to appeal to my readers and gain new subscribers. If not, what reason would I have for a blog! Last year (i.e. 2014) was a good year for me. It was a busy year! However, I still made […]
Assessing Conformance to Specifications When a client requires a statement of conformance to predetermined specifications, there are several cases where the uncertainty in measurement has an influence on the statement of conformance. To properly assess conformance, add(subtract) the estimated expanded uncertainty to(from) the measurement result and determine which of the four following scenarios apply. […]
Quantifying UUT resolution uncertainty can vary significantly depending upon a device’s design, functionality, and operation. The resolution of a digital device may not be evaluated in the same manner as an analog device or artifact. Additionally, the resolution of similar devices may vary depending on how it is used. This makes the evaluation of resolution uncertainty […]
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