What Is the Traditional Approach to Measuring the Sensor?
2019-06-25
The traditional approach has been very much a similar one—a preamplifier stage with a high input impedance to mitigate against sensor leakage effects and with high input common- mode rejection, followed by a 3rd or 4th order band-pass filter, a sample-and-hold stage, and finally an similar-to-digital conversion.
A typical similar front-end approach is shown. The sensor output signal is firstly amplified by an instrumentation amplifier. It is crucial to amplify the interested signal as much as possible, but also to avoid the amplifier output saturation by the unwanted dc common-mode voltage.
This usually limits the gain of the first stage instrumentation amplifier to no more than ×10. A band-pass filter stage further removes dc effects and reamplifies the signal into to a sample-and-hold circuit—it is this difference signal, representing flow rate—that is then sent to a digital converter.