Electrical Simulation
Calibration techniques simulate a physical load on a bridge-based sensor by placing a known resistor across one arm of the Wheatstone bridge. This shunt calibration provides a quick and repeatable method to verify the gain and linearity of the signal conditioning electronics. This approach does not require the application of actual physical forces to the transducer.
Resistance Calculation
Precise formulas determine the value of the shunt resistor needed to simulate a specific strain level. The calculation uses the gauge factor, the nominal resistance of the bridge arm and the desired simulated strain. This calculated value ensures that the resulting voltage output matches the expected physical response.
Verification Procedure
Operators activate the shunt switch to connect the resistor and record the change in output voltage. This change is compared to the baseline value established during the initial laboratory calibration of the sensor. Any difference indicates drift in the conditioning amplifier or the sensor excitation voltage.
Temperature Sensitivity
Thermal changes can affect the value of the shunt resistor and the bridge completion resistors. Using high-stability resistors with low temperature coefficients minimizes these errors during field testing. This stability is verified through periodic laboratory testing to ensure that the shunt calibration remains a reliable reference for field measurements.
Engineers must account for cable resistance when calculating the simulated strain, as long lead wires can introduce errors in the calibration results.
