Controllers receive different types of signals from measurement instruments. They make change in the current situation of the application based on the preset functions. Temperature controllers, humidity controllers and process controllers are common controllers in industry.
Indicators show different input signals including voltage, current, RTD, and TC signals and send 4-20 mA signals or active a relay to make change in system control. Panel Meter, Indicator, Counter, Timer, Digital Display Units are commonly used indicators in this category.