A temperature switch is a device that monitors the temperature and opens or closes the corresponding switching contact when a predefined switching temperature is reached. To protect the machine from overheating, the temperature switch shuts down the machine or starts the cooling fan.
The temperature switch works like a typical electrical switch in 'on-off' applications. This device can be set to respond to a specific temperature. When the switch's measuring probe detects an increase in temperature, it opens or closes the electrical contacts. When the temperature decreases, the electrical contacts close or open.
There are several ways of classifying temperature switches. Considering the state before actuation, we distinguish between normally open (NO) and normally closed (NC) switches. We also speak of switches with automatic and manual reset. With regard to the type, we distinguish between:
Temperature measurement in these switches takes place via bimetal disc. They close when the nominal switching temperature is reached.
universally applicable
high stability even with vibration - can be used in compressors or motors
small dimensions
reasonable price
no additional contactor required for switching voltages up to 25 V
less accuracy
do not allow further signal processing
temperature range limited to 200° - the connector of the bimetal switch is located close to the hot area
high accuracy
independent switching of limit values
several switching points can be set
thanks to additional analogue outputs, can also be used for other applications, e.g. continuous temperature monitoring
can be equipped with IO-Link function
direct access to measurement results via LED display
price
temperature limitation to 150°C
need for a contactor in addition to the power supply
wide temperature range up to 350°C
two switching settings possible
allows switching of low voltages (250 VAC)
no additional power supply required
no additional contactor required
The thermostat can have a temperature switch function for protection against overheating or overcooling.
Temperature switches come in two design varieties. A NO (normally open) switch means that when it is actuated, the contacts are normally open. A NC (normally closed) temperature switch means that the contacts are normally closed.
NO closes the machine circuit when the switching temperature is reached so that, for example, a fan or a warning light can be switched on. The NC switch opens and closes the machine circuit. In both cases, when the temperature falls below the reset set point, the contacts return to their normal state so that the monitored equipment can start working again.
Temperature switches are used in numerous industrial and manufacturing processes. They are particularly used in:
food and beverage industry
pharmaceutical industry
automotive industry
Typically, temperature switches are found in heating systems, air heaters, water boilers and circulation pumps