Metrology

• How to Calculate Test Uncertainty Ratio

Test Uncertainty Ratio Definition Test Uncertainty Ratio or TUR is a common term used in calibration. It is the ratio of the tolerance or specification of the test measurement in relation to the uncertainty in measurement results. According to the ANSI Z540.3 Handbook, the official definition is the ratio of the span of […]

• How to Calculate Emissivity Uncertainty

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, […]

• Local Gravity: How to Calculate Yours in 3 Minutes

Introduction In Metrology, knowing your local gravity is important if you are performing comparison measurements that involve forces that are influenced by gravity. Established at the third General Conference on Weights and Measures in 1901, the standard gravity on Earth is 9.80665 m/s2, or 32.174 ft/s2. However, standard gravity only applies to an object […]

• How to Calculate Air Buoyancy Correction with Examples

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 […]

• Top Posts of 2014

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 […]

• Conformance to Specifications and Statements of Conformance

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. […]

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• UUT Resolution Uncertainty For Different Types of Test Equipment

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 […]