Measurement uncertainty in torque calibration （测量扭矩校准的不确定性）.pdfVIP

Measurement uncertainty in torque calibration Luca G. Bochese, ASQ CQE, CRE (Boch - Milano), info@, Dr. A. Bochese ( Feanor - Tallinn), info@, Keywords: Torque, calibration, uncertainty, torque tools, torque testers Contents 1. Introduction - Abstract 2. Standard 3. Typical torque curve 4. Actual calibration procedure 5. Considerations on traditional calibration procedure 6. New torque calibration device 7. Calibration of the device 8. Calibration of reference torque tools 9. Calibration certificate 10. Measurement uncertainty 11. Acknowledgements 12. References 13. Acronyms 14. Slides 1. Introduction - Abstract Calibration of torque measurement instruments (mainly torque wrenches and torque testers), even if widely used in the automotive, aviation and building industry, has received much less attention than other types of instruments (i.e. length measurement instruments). Very few laboratories offer calibrations services for torque measurement instruments, compared to length measurement, pressure, etc. All car manufacturers have developed internal measurement systems to measure torque (i.e. braking systems, frictions, etc), but out of these laboratories the specific situation for torque calibration is still unclear. Since torque is given in Nm, the usual way to calibrate such instruments is to use a torque balance, set the torque tool at the target value (i.e. 40 Nm) and apply reference weights (N) until the requested KP (click point) is reached. The difference between the nominal KP (on the wrench) and the true KP (measured by the sensor on the torque balance) should be less than 4% or 6%, depending from tool type. This presentation focus on calibration of torque measurement and the comparison between this traditional method (torque balance) and a new calibration device, also used at the PTB Braunschweig - Germany. Experience shows that t