Basics About Temperature Controllers

General Considerations

For accurate control of the process temperature without constant operator involvement all industrial thermal process relay upon a controller. The controller gets is inputs from contact temperature sensors like thermocouple, RTD or from a non-contact temperature sensor like an infrared temperature sensor. The controller transmits an electrical signal (current or voltage) to a power switch device which can be a simple relay, a solid state relay or a SCR (Silicone Controlled Rectifier).

Remember: The temperature controller is just one part of the entire control system, so it must be selected accordingly.

The basic types of temperature controllers are:

  1. On / Off control This units turns the power on and off when the setpoint is crossed. This type of controller is adequate when the process temperature is not very critical and/or larger masses need to be heated. (like immersion tanks)
  2. Microprocessor control (PID control) This is a generic term for a control feedback mechanism widely used in thermal control systems. A PID controller attempts to correct the error between a measured process temperature and a desired setpoint by calculating and then outputting a corrective action that can adjust the process accordingly. A widely used PID controller is Ogden's ETR 9090.