A basic instrumentation system consists of a transducer, conditioning amplifier, and analog digital converter connected (in general) by analog and digital transmission lines.

The measurand is the physical quantity measured by the instrumentation system. It can be electrical such as voltage, current, resistance or capacitance as well as non-electrical such as temperature, light intensity, distance, speed, angle, etc. The measurand is converted into anelectrical signal by a transducer, amplified and conditioned, converted into a digital form and transmitted to the data acquisition system.
It is not always possible to place the transducer, the signal conditioning amplifier, the analog digital converter, and the data acquisition systemin one place. Thus they have to be connected by the transmission lines.