Temperature controller

Temperature controllers in automated processes

Temperature controllers are used to display and control the temperature in processes. Temperature sensors supply the measured temperature value to the control unit. The controller regulates the temperature according to the setpoint. Heating controllers, for example, switch on a heating device when the temperature falls below the setpoint and only switch it off again when the setpoint is reached. Cooling controllers work in the opposite direction. A cooling device is switched on when the setpoint is exceeded and switched off again when the temperature falls below the setpoint. Depending on the unit variant, a different control type is executed.

Temperature controllers play a crucial role in the proper functioning of various industrial and HVAC processes. These devices are designed to maintain a specific temperature setpoint, ensuring that equipment operates efficiently and safely. Temperature controllers are commonly used in applications such as refrigeration, food processing, pharmaceuticals and manufacturing.

Choosing the right temperature controller for your application is crucial, as an incorrectly sized controller can lead to appliance damage, wasted energy and reduced efficiency. In addition, temperature controllers should be regularly maintained and calibrated to ensure optimal performance over time. To summarise, temperature controllers are important devices that contribute to the smooth operation of various industrial processes.

Control types of temperature control

Simple basic tasks are controlled with 2-point control, while devices with PID control are used for very precise control tasks. Depending on the application, the temperature controllers are either installed in control panels or mounted in control cabinets on top-hat rails. If the settings and the temperature setpoint are changed frequently, it is advisable to mount them in a control panel to ensure good accessibility. Depending on the variant, the settings and the temperature setpoint on the unit can be protected with a password to protect access from unauthorised persons and to prevent faulty control.

2-point temperature controller

2-point controllers are ON/OFF controllers for simple control tasks. High accuracy is not required from these units. The decisive factor in selecting this variant is the reliable implementation of simple temperature control. When a threshold value is exceeded or undershot, the output is switched to control the heating. In addition, some temperature controllers offer a hysteresis function to keep the temperature within a required range. These controllers are ideal for simple temperature control and offer a cost-effective solution compared to more complex PID controllers. These devices are used, for example, in cold rooms or refrigerated cabinets such as freezers in supermarkets to keep the temperature permanently at the required level.

If the units have a timer for which the duration of the temperature control can be set, they are particularly suitable for use in ovens, for example. As product variants, the devices are equipped with additional functions. A buzzer linked to alarm values warns the user, for example, if the temperature exceeds or falls below the desired temperature range, whether the timer time has expired or whether there is a sensor defect. Hysteresis function and offset settings enable precise and also flexible adjustment. The control process is mainly switched with a relay if the switching cycle is not too high. With higher switching cycles, the output relay is heavily stressed and thus reaches the end of its service life earlier. In this case, the use of a solid-state relay is the appropriate solution, as there is no mechanical wear due to high switching cycles.

PID temperature controller

PID controllers (proportional-integral-derivative) control the temperature very precisely to prevent a constant deviation from the setpoint. The control mode of these units can be set to P (proportional), PI (proportional-integral) or PID. The special feature of these units is that they are self-learning. Feedback is given on the controlled value. The measured value is automatically compared with the ideal value and, if necessary, an appropriate adjustment is made. Over the runtime, the temperature control thus becomes more and more accurate. Furthermore, the controller can adjust to changed conditions with the help of the self-optimisation function in order to permanently achieve precise control.

The operation of the PID control algorithm is thus controlled by receiving feedback from the process at regular intervals. As a result, the control of the switching output is continuously corrected. Units that work with PID control have a high degree of accuracy and adaptability. Due to the fast control frequency, a solid state relay is often used at the control output, as mechanical relays might wear out in a short time. A PID controller that does not generate an output signal only checks the process sequence for errors if, for example, a 2-point controller performs the control. Furthermore, it is examined how often the error occurs and whether it occurs upwards or downwards.