What is a temperature controller, the working principle of a temperature controller, and the differences between temperature controllers

What is a temperature controller

Simply put, a thermostat is an instrument used to control temperature. The thermostat obtains input signals from temperature sensors and outputs the output signals to connected control components such as heaters or fans.

The principle of temperature controller

In order to achieve mechanical automation and accurately control process temperature without human operation, it is necessary to equip the temperature control system with an intelligent temperature controller. The characteristic of an intelligent temperature controller is to receive input signals from temperature sensors such as thermocouples or RTDs, compare the actual temperature with the desired control temperature (also known as the set value), and finally transmit the output signal to the control element. The controller is a part of the entire control system, so when selecting an appropriate controller, the entire system should be analyzed.

When selecting a controller, the following factors should be considered:

1. Required output type (T: thermocouple R: thermal resistance L: linear signal)

2. Required control algorithms (on/off, proportional, PID)

3. Output type (S: Transistor C: Current V: Voltage)

4. Number of channels (4000:4 channels 3000:3 channels 2000:2 channels)

Differences in temperature controllers of different types

There are three basic types of controllers: switch, proportional, and PID. According to the controlled system, operators can use one of the types for process control.

On/Off Control

A switch controller is the simplest type of temperature control device that can perform switch control operations. The output of such devices is either on or off, with no intermediate state. The switch controller will only switch outputs when the temperature exceeds the set value. The controller is installed using standard rails, and the wiring uses highly reliable plug-in terminals, making it very easy to install and maintain in engineering. Combining local control buttons and circuit status indicator lights, debugging is very simple and convenient. The controller reserves an emergency signal (such as fire protection) interface, which can ensure the fixed requirements for special lighting equipment in emergency situations.

Proportional control

Proportional (P) control is a control method,

Proportional control is the simplest control method. The output of its controller is proportional to the input error signal. When there is only proportional control, there is a steady-state error in the system output.

PID control

The PID controller can achieve very strict control, but the PID algorithm needs to be tuned. PID self-tuning temperature control can achieve this function. This type of controller introduces integral and differential control, also known as PID control, on the basis of proportional control. This controller combines proportional control with two other adjustment mechanisms to help the device automatically compensate for changes in the system. Integral and differential adjustments are expressed in units of time, also known as "reset" and "rate" adjustments, respectively. Proportional, integral, and differential terms must be adjusted or "tuned" for specific systems through repeated trial and error. Among the three types of controllers, PID controllers have the highest accuracy and stability, making them most suitable for systems with relatively small masses and systems that are highly sensitive to changes in energy during the process. For systems with frequent load changes, as well as systems that require automatic compensation through controllers due to frequent changes in set values, available energy, or controlled mass, it is recommended to use such controllers. Weierna High Tech provides multiple controllers that can automatically adjust themselves, namely self-tuning temperature controllers.

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