A signal conditioning circuit is all that takes signal from real world through its sensor and create
a voltage or current change according to the target physical change.
A calibration process is needed to relate between voltage output and actual physical change.
The voltage change is now needed to feed to a micro controller for further study or display or
simply to actuate any mechanical arm or in even simpler case to switch or regulate another circuit.
The ad conversion is one of the important thing in automation or control Engineering. In older circuit ADC0804 or such devices used but this can be done by a micro-controller today as there
are micro-controller with built in ad conversion is available now.
All you need to know to write the proper code for it.

A1KITS

Solution for all micro controller is found on net
lets try in this blog with a different view.