4–101 Instrumentation Amplifier with Alarm Strain gauges measuring the deflection of a sintered metal column are connected to a Wheatstone bridge. The output of the bridge is balanced when there is no strain producing 0 V output.

As the column is deflected, the bridge produces 150 μV=Ω

change caused by the strain gauges. The maximum possible defection would result in a 4-Ω change. Design an instrumentation amplifier that can take the voltage created in the bridge and send it to a 0 – 5 V ADC, where no deflection produces 0 V at theADCand maximum deflection produces 5 V. To avoid loading, send the output of the bridge to a very high input resistance differential amplifier. The columns being tested are brittle and can shatter violently if the conditions cause the strain gauges to change by more than 3:9 Ω. For safety, connect the output of your instrumentation amplifier to a comparator circuit that will trigger an alarm when the strain causes the resistance to change by 3:75 Ω. The alarm needs to be triggered by 15 V.