Question

A capacitive sensor is to be used to measure relative humidity (%RH) of
air. The sensor has an input range of 1–99% and a sensitivity of 0.34 pF/%RH. Assuming a
linear input-output relationship, design a suitable deflection bridge for converting the change in
capacitance to a change in voltage. The sensor supply voltage should be in 8–10 V.
Note: A capacitive bridge will need an a.c. supply voltage, but it is only the amplitude of
the bridge output which is of interest. Discuss how this can be exploited in order to simplify
data acquisition and analysis of measured data.
There are plenty of degrees of freedom, so motivate your design choices clearly.

Answer 1