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Shunt Calibration

Shunt calibration (Rcal) is a method for determining the full-scale output of a pressure transducer by electrically simulating a full-scale load. Either a shunt resistor is applied to the transducer circuit, or voltage is applied to an ancillary circuit designed to generate a full-scale output. That output can then be measured precisely to calibrate your control system’s reading of the pressure transducer.

Shunt Cal works on piezoresistive strain gauge-type pressure transducers. Four of these small gauges, which convert changes in mechanical strain and compression (due to pressure changes) into changes in electrical current, are connected in Wheatstone bridge formation. At minimum pressure the strain gauges produce minimal current; at full-scale pressure the gauges allow peak current flow.

For simple, unamplified signals, Shunt Cal simulates maximum compression by placing a known resistor in parallel with one of the strain gauges (i.e., shunting the gauge), which drives the output to 80% of maximum. For transducers with input and output conditioning, an ancillary circuit designed to generate a full-scale output is powered up. Either way, Shunt Cal allows you to validate the full-scale output of the transducer.

There are two primary purposes for using Shunt Cal: one, as noted above, is calibrating your control system equipment that will be communicating with your transducer; the second is confirming that your transducer is functioning properly.

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