Precision Instrument Correction reposted this
Calibrating a few AKO Torque transducers in our lab today, I was thinking of something interesting to post and figured this could be it. Things that a lot of users of torque wrench’s and torque instrumentation commonly do is miss use the terms inchpounds, in.lbs, and closer to the true unit of measure, lb.in, but this is still wrong. The proper unit of measure here is lbf.in, or pound-force.inch, the critical thing here is force. Torque is not a calculated value derived from mass and length but rather force and length. When us as calibration technicians or metrologists are performing calibrations in the lab, missing the step of calculating your applied mass into force, this can and will cause a tremendous amount of uncertainty to your measurement, and ultimately an incorrect measurement. #metrology #torque #force #caibration #torquecalibration #uncertainties
NIST 811 covers many definitions and torque is always force x length. Excellent post. Now if we could only get AKO and other manufacturers to start using the right units 😂. https://www.nist.gov/pml/special-publication-811 And I challenge anyone to find an example of a manufacturer using Metre Newton - Meter Newton.
Semantics aside, torque is the force generated by mass x length. NIST now uses a system akin to a Kibble balance to realize torque. That does not alter the fact that a weight acting on an arm is the practical realization of the force. “Following the 2019 redefinition of the kilogram in the International System of Units (SI), realization of torque no longer needs to be traceable to physical mass and length artifacts using a calibrated weight suspended from a known lever arm.” From NIST https://www.nist.gov/noac/technology/mass-force-and-acceleration/torque-realization#:~:text=The%20device%2C%20known%20as%20the,torque%20in%20the%20horizontal%20plane.
Simply use the SI for traceability purpose and you do not have to think about pounds and inches. 🙂
ASTM E2428 is Great reference for calibrating torque transducers, including uncertainty elements when using a dual radius arm.
Laboratory Manager at Precision Instrument Correction
10moHenry Z.