With measurement chain, we refer to the set of stages of a measuring instrument, which process the information detected by the physical quantity (object of study), to then present a result: i.e., the measurement. The main stages of a measurement chain are three:
- the first stage consists of a sensor and/or a transducer in contact with the physical quantity to be detected (also called the primary sensitive element). In measurement chains that include more than one transducer, crosstalk effects can occur, and the cause of this effect is to be found in capacitive and inductive couplings that can occur in the transducers themselves, in the connection cables, and finally, in the block of manipulation;
- the second stage consists of an intermediate signal processing system or signal conditioner which converts the information coming from the previous stages into a form such as to adapt to the acquisition system. Typical operations performed by the conditioning circuit are noise filtering, linearization of the transfer function, conversion, and amplification of the signal generated by the transducer. The output signal from the measurement chain can be analog or digital. The power supply provides the electrical power necessary for the operation of the various electronic devices used in the measurement chain. The sensor is not powered when it draws the indispensable power for information from the outside world as it happens for thermocouples and piezoelectric sensors;
- the third stage is represented by the terminal instrument which indicates the result of the operations carried out by the previous stages, which provides the operator with the value of the measurement.