My whole circuit is a humidity sensing/control circuit. I have got a sensor that senses humidity; however its output is capacitance (the capacitance across its terminals changes with change in humidity). The challenge with it is the range of the capacitance change is very small (about 200 Pico farads). Secondly, this capacitance has to be fed to a microcontroller. The microcontroller only accepts voltage signals as its inputs (or so I think). The controller is PIC 16F877A. I was advised to convert the capacitance to voltage using a weihn bridge then amplify the resulting voltage using LM744.
I have done this but I am not making headway with both the weihn bridge circuit and the amplifier. Can anyone help with values of components I can use and help with the circuit design?
I have done this but I am not making headway with both the weihn bridge circuit and the amplifier. Can anyone help with values of components I can use and help with the circuit design?