Excitation

Excitation is the external electrical voltage and/or current applied to a transducer for its proper operation (often referred to as the supply current or voltage).

Active transducers can be excited using a controlled current or voltage. The choice between voltage and current excitation is generally at the discretion of the designer. In data-acquisition systems, it's not uncommon to see constant-voltage excitation used for strain and pressure sensors, while constant current excitation is used to excite resistive sensors such as RTDs or thermistors. In noisy industrial environments, current excitation is generally preferable due to its better noise immunity.

There are two major factors in selecting an excitation source that will enhance overall system performance. First, resolution: the magnitude of the excitation should be sufficient that the minimum change in the variable being measured produces an output from the transducer that is large enough to overcome the noise and offset in the system. Second, power level: if the sensor is resistive the designer must ensure that the self-heating effects of excitation current flowing through the transducer do not adversely affect the measured results.