Our last blog, Device Resolution and the Impact on Consumer Risk, described why best practices should be followed for conformity assessments rather than drafting individual test protocols and standards. How should manufacturers and calibration laboratories correctly calculate both uncertainty and risk on equipment? Risk, Conformity Assessment, and the Decision Rule ISO/IEC 1702:2017 addresses how to […]
If a device's uncertainty has too coarse of a resolution, then you need a device that does not subject the conformance decision to higher risk. This blog will present examples that demonstrate why best practices should be followed for conformity assessments rather than drafting individual test protocols and standards. Best practices are outlined in guidance […]
In looking at various equipment, it seems the force equipment in the test and measurement industry specifically has mainly specified tolerances as a percent of full scale. Several crane scales, tension links, hand-held force gauges follow this trend when determining accuracy or tolerance. There are a few manufacturers who use % Indicated Value (IV). My […]
Figure 1 Graph Showing Method 5 Acceptance Limits Several organizations and publications reference or insist on maintaining a 4:1 Test Uncertainty Ratio (TUR) without understanding the level of risk that they may be subjecting themselves to. The general thought is as long as the lab performing the calibrations has standards at least four times better […]
Various calibration laboratories are using hydraulic, screw, and other force calibration machines where it is difficult not to overshoot a test point. By talking about overshooting a test point we are referring to loading past the desired point and then letting the creep in the hydraulic system naturally decrease the force point. Overshooting the force point […]
Most calibration laboratories will say a device is "In Tolerance" without considering the uncertainty of their measurement process. This equates to you not using a calibration laboratory that has standards to meet your needs and accounts for measurement risk properly. Most ISO/IEC 17025 accredited calibration labs that use secondary standards have Calibration and Measurement Capability […]
Calling an instrument “In Tolerance” is about location, location, location. It’s also about the uncertainty of the measurement, but a bad location is going to raise the Probability of False Accept (PFA) significantly. The probability of false accept is the likelihood of a lab calling a measurement “In Tolerance” when it is not. The location we […]
Metrological Traceability, Measurement Uncertainty, and Measurement Risk About a year after turning 40, I bought a pair of reading glasses. After another year, I started noticing a decrease in my overall vision and figured I needed to visit an eye doctor. I went to an ophthalmologist to have my eyes tested, and the doctor said […]
Bad Measurements Happen! Technicians are Fallible! The Wrong Equipment is Used! Almost everyone has had problems related to bad measurement practices—some of which have resulted in serious devastation. There was the BP oil refinery explosion in Texas, the Hubble telescope with improper focus, the Space Shuttle explosion, a Stealth Bomber crash, Cox Health’s overdosing of […]
