Overview

Strain gauge based transducers should be calibrated by applying the appropriate load to the transducer and measuring the resulting output. Strain gauge pressure transducers should be calibrated by applying pressure. Strain gauge load cells should be calibrated by applying dead-weight loads or hydraulic piston loads monitored by a proving ring or reference load cell. Strain gauge torque transducers should be calibrated by applying dead-weight loads to a torque arm or by using a torque wrench calibration machine.

When strain gauges are attached to equipment to determine stress levels and distributions, the ideal calibration method is to load the equipment at a known stress level and stress distribution and to monitor the output of the installed strain gauges. In many cases, this method is not practicable, and the user must rely on the shunt calibration method. Shunt calibration is carried out by placing a large value resistor in parallel with one of the arms of the strain gauge's Wheatstone bridge to simulate a reduction in the resistance of that arm and a resulting unbalancing of the bridge. This is a simulation of the applied load, and the resulting strain gauge output is calculated from the known characteristics of the gauge and the measurement system. Since this method is a simulation, it can never be considered a true calibration since there is no standard used as a reference. The method is suitable for the majority of strain gauge applications where the user wants to demonstrate that the operation of the equipment produces...