Channel Config: Shunt Calibration
Shunt calibration is used for strain gauges. It requires Wheatstone bridge conditioning for the channel, with a set of shunt resistors fitted. It is a live calibration that requires the strain gauge to be fitted during calibration.
Shunt calibration is a variation of DC calibration, for which the points are taken automatically: the system will activate in turn the various shunt resistors (to simulate different strain) and take a measurement. For each measurement taken, the simulated strain will be computed, based on the shunt resistance applied and other settings specified in the shunt cal tab.
Depending on the type of conditioning used (and therefore the number of shunt resistors available), the number of points taken will vary between 2 and 4.
- Gauge Resistance: the nominal resistance of the strain gauge. Value is in Ohms.
- Shunt Resistance 1: in Ohms, the resistance of the first shunt resistor fitted in the signal conditioner. A default value is filled in automatically, based on the conditioning fitted on the channel. This can be overridden.
- Shunt Resistance 2: the resistance of the second shunt resistor fitted in the signal conditioner (if there is one). 2 shunt resistors provide 4 shunt resistance values: resistor 1 alone, resistor 2 alone, both in parallel, and neither applied.
- Gauge Factor: the gauge factor associated with the strain gauge, commonly this is a value around 2.
- Cable Length (m): the length of the cable connecting the gauge to the conditioner. This is in metres and is optional and only required if line resistance is required in the calculations for the calibration.
- Ohms Per Metre: the Ohms Per Metre rating of the cable used to connect the strain gauge to the conditioner. This is optional and only required if line resistance is required in the calculations for the calibration.
- Young’s Modulus (from µε to “X”): the modified Young’s modulus to convert the value from the calibration equation from microstrain (µε) to the unit associated with the selected channel.
- Shunt Cal Item: the integer item number associated with this channel. This can be used to group channels together for calibration.