Analog Circuits
Ralph Morrison · 2016
This chapter deals with the general problem of analog instrumentation. The signals of interest are often generated while testing functioning hardware. Tests can take place over time, in a harsh environment, during an explosion, during a flight, or in a collision. The chapter also focuses on analog circuits that operate below 100 kHz. The availability of integrated circuits has simplified many aspects of analog circuit design. Instrumentation must often handle long signal lines, reject ground potential differences, and maintain circuit stability. The general problem of analog design is called signal conditioning, which includes gain, filtering, offsets, bridge balancing, common-mode rejection, transducer excitation, and calibration. Measurements of temperature, strain, stress, position, and vibration are an important part of many development efforts. In vibration analysis, the sensing transducer is often a quartz crystal. This crystal is electrically equivalent to a capacitor.