Temperature switches are employed in machine building and other industrial applications for limiting temperature. They monitor the temperature and react at a predefined point. To protect from overheating they either switch the gear or machine off or activate a fan for cooling. Based on the task accessible, temperature switches operate as either normally-closed or normally-open switches. Three switch types are considered for industrial applications:
Electronic switches
Example: Electrical WIKA temperature switch TSD-30
In which a higher accuracy is requested, the operator should resort to an electric switch. With this instrument, you can change the limit values yourself and set several switch points. Electronic temperature switches can be utilized beyond their actual function ? yet another analogue output (e.g. 4 ? 20 mA) enables further processing of the signal and thus continuous temperature monitoring as well.
Furthermore, switches of the type can be fitted with digital communication (IO-Link). The benefits of these are an even faster parametrisation along with extended diagnostics functions and integration into automated processes. Via an LED display, an on-site indication can also be provided.
The wide usability of the electronics is reflected in the purchase costs. It also sets limits on the operating temperature. Its maximum value is, normally,150 �C, that is sufficient for the majority of applications, however. So that you can fulfil their tasks, electronic temperature switches need, and a power source, yet another contactor since their transistor only switches suprisingly low power.
Dial thermometers with switch contact
Example: WIKA expansion thermometer with switch contact SB15
The outstanding feature of dial thermometers with switch contacts may be the wide temperature range. Generally, Natural are used for industrial applications. They cover ? depending on the version ? temperatures around 400�C.
This instrument type also offers the operator the possibility of selecting multiple switch points and setting them independently. It is also ideal for switching in the low-voltage range (250 VAC). Yet another contactor isn’t needed. Dial thermometers with switch contacts function without additional power and, furthermore, offer an on-site display. An additional processing of the signal isn’t possible, however.
With Agony to price and performance, the switch solution described here is situated in the mid range.
Bimetal temperature switch
Example: WIKA bimetal temperature switch model TFS35
Bimetal temperature switches have become compact, cost-effective and have been designed for a variety of applications. These instruments may also switch with low voltages up to 250 VAC, and with this they can manage with no additional contactor.
Bimetal temperature switches operate with lower accuracy. Working exclusively as switches, they neither offer a local display, nor do they enable any processing of the signal. Their compact design also only permits a restricted temperature range (max. 200 �C), because the plug connection is very close to the hot area.
Note
Further information on the TSD-30 electronic switch, on the SB15 dial thermometer with switch contact and on the TFS35 bimetal temperature switch are available on the WIKA website.
Also read Happy : So how exactly does the IO-Link work?
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