Strain Gauge and Wheatstone Bridge

This model shows how to model a strain gauge and measurement amplifier. The strain gauge forms one leg of a Wheatstone bridge, which is connected to a differential amplifier. A second op-amp is then used to both amplify and apply a low-pass filter to the measurement signal. The op-amps are modeled at a system level, with the user specifying parameters such as open-loop bandwidth, gain and maximum slew rate. In this circuit, the dynamics are primarily set by the low-pass filter. The op-amp bandwidth and maximum slew rate have little impact on the step response.

Model

Simulation Results from Simscape Logging

This code plots the actual and measured strain from the model of StrainGaugeWheatstone resulting from two tests. The first test sets the resistor and capacitor in the low pass filter to the maximum value of their tolerance ranges. The second test sets the values for those components to the minimum of their tolerance ranges. The plot shows the effects this has on the strain measurement.

Results from Real-Time Simulation

This example has been tested on a Speedgoat Performance real-time target machine with an Intel® 3.5 GHz i7 multi-core CPU. This model can run in real time with a step size of 50 microseconds.