Temperature monitoring or control devices are essential in any temperature control loop. These units will indicate actual temperatures and by setting a required temperature the controller will switch a device on or off viz element, fan, actuator, valve etc.
Temperature controllers are split into 3 groups namely digital, analogue or percentage.
Digital controllers use microprocessors to store and correlate data thus are extremely fast , accurate and highly repeatable. They are also programmable thereby being flexible in their functionality to improve control performance and accuracy around setpoint.
Analogue controllers use simple electronic components and are limited in their functionality, yet serve a vital role in many temperature control applications where accuracy is not essential. These devices generally use simple relay outputs to switch processes on or off.
Percentage controllers are devices which have no input signal from a temperature sensor. They limit the output voltage by using a simple electronic circuit, and by merely increasing or decreasing the voltage output, one determines the necessary heat required for an element to perform its task.