Sensor Calibration for Fastener Testing

System vs. Shunt Calibration

When setting up a readout instrument or data acquisition system to read an RS Technologies torque or load sensor, it is important to have the shunt calibration resistor and the associated Auto Cal value available for use in matching the transducer to the data acquisition device. Learn more about performing a System Calibration or a Shunt Calibration based on the location and parameters of your test.

Strain gaged load and torque sensors will typically require calibration prior to use. Calibration of these devices matches the data acquisition equipment (DAC) to the performance of the load or torque sensor. One method, called System Calibration, connects the sensor and DAC and applies a known load or torque to the sensor. The gain or span of the DAC is adjusted so that when a load or torque is applied in the laboratory or field, the displayed and/or recorded value will be accurate.

Often, when it is not possible to apply a known, certified load during calibration when the devices are being used in the field or on an assembly line, a useful method called Shunt Calibration is available. This method takes advantage of the electrical design of a strain gage transducer such that when a precision resistor of a specific impedance is temporarily connected to the +Power and +Signal of the sensor, a signal offset is produced. This signal offset is converted into engineering units and is provided on the Calibration Certificate as a Shunt Cal value or Auto Cal value. This Auto Cal value can then be used to adjust the gain of the DAC and scale the output of the sensor to the readout using hardware or software adjustments. This is the method of calibration used for most of the RS Technologies strain gaged torque and load devices.