square wave input to lvdt and what are the demodulation techniques for square wave?

If it is an + square wave just add a diode and a cap.
If it is an AC square wave add a bridge rectifier and a smaller cap.
LVDTs NEED sinewave excitation if you want a chance of linear outputs.

The standard methods usually use a phase-sensitive detector, but Analog Devices do the AD598, which does the excitation and demodulation for you.

iceng1 year ago
The linear variable differential transformer
generates a voltage proportional to displacement of an iron rod
this makes the device a great electronic measuring stick for motion
like a water tank or a plant growth or a sub conscious smile.