Two metals connected to one another, which have different thermal expansion. Due to this difference in expansion, a bimetal strip bends or a bimetal disc cracks when the limit temperature of a material is reached.
When a predefined ambient temperature is reached, two metals firmly connected to one another cause this pane to suddenly jump over. The resulting force is used to suddenly separate or close an electrical contact.
- Bimetal switches are purely mechanical switches that react to changes in temperature and switch an electrical contact. A bimetal switch can be used directly in an application to regulate, monitor or limit temperatures. Depending on the switching capacity, no further components are necessary. The „sensing“ of the temperature and the electrical circuit or control are contained in one compact component.
- Sensors are passive components that are integrated via an electronic control and determine the temperature by changing the resistance. Here the sensor only has the function of „sensing“ the temperature and converting the temperature into a resistance value. The actual evaluation and regulation is carried out by a corresponding electronic device. This must be available or purchased separately.
- Bimetal switches are suitable when simple control or limitation of the temperature is to be carried out, since only a single component is required here. As a rule, the use of a bimetal switch is therefore much cheaper than the combination of sensor and electronics.
- Sensors are suitable when very high demands are placed on the accuracy of the temperature detection, or when several temperatures have to be recorded. Temperature sensors are relatively small and can also be used where space is limited.
- A controller is a switch that keeps a temperature within a certain range. This is determined by the response temperature and the differential (difference between switching on and off).
- A protector is a switch that detects a disruptive temperature range and temporarily switches the circuit off or on. Like the controller, the protector automatically switches back to its starting position after it has cooled down accordingly. The differential is significantly larger than that of the controller.
- Both versions are only available as „openers“. This means that a circuit is interrupted when the set response temperature is reached.
- A limiter switches off a circuit when the set response temperature is reached. The circuit remains interrupted until a reset pin or reset button is pressed. So an “action” is required that prompts the user to address the problem that has arisen. This is one of the first safety levels if an impermissible temperature is reached, which indicates a malfunction in the application. After pressing the reset button, the limiter is switched to continuity again and the application can continue to be used, provided the triggering error has been eliminated.
- A fuse switches off the circuit permanently when the set response temperature is reached and cannot be reset. A thermal fuse is usually used when the resulting temperature indicates a critical error and the application should be switched off permanently.
- Closer contacts are generally used when a set ambient or surface temperature is reached, a circuit has to be closed in order to switch on a signal transmitter or a fan. (Example: PC fan is switched on if necessary)
- Controllers are then used to keep a temperature in a certain range or to detect a slightly incorrect temperature in a first stage and to interrupt further operation for the time being to allow the system to cool down. When the switch-back temperature is reached, the application is automatically restarted.
Bimetal switches are tested and certified for switching cycles. A shelf life over a pure period of time cannot be defined, as this depends very much on the ambient and operating conditions.
- A switching-cycle is the first switch (opening or closing of the circuit) and switching back to the initial state.
- A circuit is a one-time change in the switching status.
- The transfer of the temperature depends on the switch type. There are contact switches such as the 03EN series or the S01 series, in which the temperature-sensitive bimetal disc lies directly on the switch base. With these switches, the temperature is mainly recorded from the floor. For this reason, a good connection between the surface to be monitored and the switch base is important.
- With switch types such as the MQT or UP, the temperature-sensitive bimetal element is in the middle of the switch and therefore these models react to the effects of temperature on all sides.
Basically, the switches can be integrated into the circuit using a plug or a stranded wire. But our strength also lies in the fact that we assemble the switches according to your wishes. We also supply complete cable harnesses with switches or fuses.
Most switches have retaining clips or screw-on brackets to screw them directly to a surface. There are also switches with threaded bolts for screwing in or pipe clips for mounting directly on pipes up to 7/8 inch in size.
We have explained the structure in detail in the configuration card for the different series.
There are switches such as the 03EC series that are specially certified for DC voltages up to 48VDC.
Most switches are approved and certified for 230VAC.
The 43X series is suitable for 480VAC.
Since a circuit is closed or interrupted directly with the bimetal switches, moisture plays a central role. Basic switches normally have no moisture protection and it is important to ensure that no moisture gets on the switch or the switching contacts during use. However, there are special series that offer temporary protection against moisture (e.g. dew or condensation). This is documented in IP protection classes or based on IP protection classes. However, special immersion sleeves must be used for permanent use in or under water.
Bimetal switches are generally referred to as Klixxon. The origin comes from the American company Texas Instruments which called their TXE series „Klixxon“. The term has been adopted into common parlance over time and has also established itself among other manufacturers.
Bimetal switches are safety products. Therefore, detailed advice is the cornerstone for successful use in your application. There are very different facts to consider. We are happy to help you with all questions relating to thermal protection in your application. As a rule, we ask about the following topics: the exact task of the switch, current and voltage, fastening and heat transfer, environmental influences
In the case of safety-relevant applications, tests under worst-case conditions are absolutely necessary in order to really get a reliable solution. We therefore always recommend a test with functional models!
We have many series in different configurations in stock and can usually manufacture customer-specific switches at very short notice. Sometimes, however, special components are also necessary. Then you have to inquire about our current delivery times.
We deliver and supply small and medium-sized quantities in batches from 1 piece to 20,000 pieces