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Temperature controllers ensure safety and take off your work
Temperature controllers are controllers that use a temperature sensor to measure the current temperature . . A control unit initiates a control circuit in the event of deviations from the desired temperature range . This allows a temperature curve to be monitored and optimized. For example, temperature controllers are used as thermostats on heaters.
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How do temperature controllers work?
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Which temperature controllers are available?
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What was to be taken into account when selecting temperature controllers?
How do temperature controllers work?
Controllers determine differences between actual and setpoint values and then specify a value for the control variable . For example, a temperature controller can be set so that°° it does not take any action at room temperature at values between 18 C and 22 C, but initiates a heating or cooling when it is below the temperature.
Temperature controllers are installed in control circuits that set a specified temperature as a control variable x to a setpoint w and keep it as constant as possible there . This is done by moving a manipulated variable that causes a change in the control variable, i.e. the temperature.
In terms of construction, temperature controllers consist of a temperature sensor, an actuator and an actuator
- The temperature sensor measures the current temperature.
- The actuator changes the actuator if deviations from the setpoint value (control difference e) occur and the temperature controller counteracts accordingly.
- The actuator is used to initiate any necessary countermeasures by connected components in the control circuit.
Temperature controllers often combine sensors and control units in one component. This is then connected to heating or cooling systems in the control circuit, which implement the temperature changes up to the setpoint and actual values. Devices other than the following components, such as warning lights or signal loudspeakers, are also conceivable, which draw attention to the critical temperature status.
In operation, temperature controllers are often based on a mechanical interaction of a temperature-dependant liquid expansion and a microswitch that is triggered by this. The microswitch can have different positions and can also be used as an electrical switch.
In most cases, the control process of temperature controllers is implemented by electronic controllers. At the output of the temperature controller, control circuits are attached, which control subsequent devices and components in such a way that the temperature is optimized by their operation or deactivation.
By the way: Nowadays only rarely analogueue control processes are used. There are exceptions at particularly high temperatures or at stock plants.
Which temperature controllers are available?
Themostats
Temperature controllers consist of a temperature sensor and a control unit. The sensor measures the current temperature, the control unit compares it with the set values and initiates any necessary countermeasures. Temperature controllers are available in simple versions with fixed values and as adjustable models, which permit an extended range of applications.
Universal controller
Universal controllers are programmable temperature controllers . They are used for process controls with variable parameters. So-called unit signals are processed at the input and output of universal controllers, which is why these models are compatible with devices from other manufacturers and function in a common control loop.
Temperature monitor:
Temperature monitors monitor compliance with the setpoint temperature. They are coupled to electronic control circuits that activate or deactivate other components to influence the temperature if the temperature falls below or exceeds the permissible temperature range. For example, temperature limiters are used in irons. Its function is to shut off the heating elements by disconnecting the circuit when the set maximum temperature is reached. Temperature monitors are also used in the food sector to ensure temperature specifications during processing and storage.
temperature limiter;
Temperature limiters are used for safety purposes in devices and systems. An electronic switch is coupled to the temperature sensor on the limiter. It can be an NC or NO contact that triggers at a certain temperature threshold.
Info: It is important to know that temperature limiters do not return to their initial position on their own . The control circuit remains in this position until maintenance work has been carried out if a safety temperature limiter has tripped once.
Indoor Thermostats
Room thermostats are temperature sensors with control units for optimizing the room temperature in buildings.
Built-in thermostats
Built-in thermostats are used for simple temperature control, for example in building technology for controlling heating processes. They are available in analogueue and digital versions. In some cases, digital thermostats can be conveniently controlled on the computer.
Moisture regulator;
Humidity controllers have additional sensors for measuring the humidity. They are used where not only the temperature but also the air humidity is to be optimized. For example, there are humidity regulators in greenhouses, in storage rooms or for drying basements. In these cases, they control when air humidifiers or fan heaters are automatically put into operation.
What was to be taken into account when selecting temperature controllers?
When selecting a suitable temperature controller, the question arises first of all, at which temperatures it is to be used: There are many temperature controllers for the usual room and ambient temperatures, models with wide play downwards for applications such as in cold stores and for research purposes, and also temperature controllers for extremely high temperatures, for example in metal-working furnaces.
In addition to the desired temperature range, the tolerance for the tripping behavior in some applications also plays a decisive role. For example, in research laboratories or in temperature-sensitive manufacturing processes, fluctuations of less than 0.5° C are already a disaster. Temperature controllers, which are supposed to do real precision work in such scenarios, are much more expensive.
The temperature sensor as a sensor must be designed in such a way that it can be fitted as precisely as possible at the desired location. For this purpose, there are different types of sensors, among others, which also measure correctly in liquids or in inert gas atmosphere.
In general, you should pay attention to the mounting options offered before choosing a specific temperature controller. Often there is a measuring line between the sensor and the measuring station with a temperature controller display. An extension is especially required if the control unit cannot or should not be installed directly at the measuring site.
The operating voltage must first be observed for electronically controlled control circuits. Not only the specification in volts is relevant, but also whether it is a temperature controller for direct voltage (DC) or for alternating voltage (AC).
The processing functions that the control unit of the temperature controller itself can perform differ considerably from one device to another:
- 2-point controllers can only assume, on or off two switching states. In theory, they do not have a time response unless otherwise established within the switching environment. Two-point controls are built into an iron, among other things.
- Universal controllers are programmable temperature controllers, which also communicate smoothly with devices from other manufacturers via unit signals.
- In between, there is a wide range of devices that can be configured for individual purposes.
The question also arises as to the type and number of outputs for the transmission of the analogue or digital signals of the temperature controller to the following components, such as heating and cooling elements. Suitable connections are required for the integration of the temperature controller into a control loop. Only a few models still work with analogue inputs and outputs, most of them are now electronic . Complex electronic temperature controllers can have several relay or transistor outputs, for example.