Temperature switches are used in machine building along with other industrial applications for limiting temperature. They monitor the temperature and react at a predefined point. To safeguard from overheating they either switch the equipment 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
Where a higher accuracy is requested, the operator should resort to an electronic switch. With this particular instrument, you can change the limit values yourself and set several switch points. pressure gauge 10 bar may be used beyond their actual function ? an additional 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 a straight faster parametrisation alongside extended diagnostics functions and integration into automated processes. Via an LED display, an on-site indication can 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, on average,150 �C, which is sufficient in most of applications, however. So that you can fulfil their tasks, electronic temperature switches need, in addition to a power source, an additional contactor since their transistor only switches very 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. In general, expansion thermometers are used for industrial applications. They cover ? based on the version ? temperatures around 400�C.
This instrument type also offers the operator the chance of selecting multiple switch points and setting them independently. Additionally it is 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. A further processing of the signal isn’t possible, however.
When it comes to price and performance, the switch solution described here’s positioned in the mid range.
Bimetal temperature switch
Example: WIKA bimetal temperature switch model TFS35
Bimetal temperature switches are very compact, cost-effective and also have been designed for an array of applications. These instruments may also switch with low voltages up to 250 VAC, and with this they are able to 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 limited temperature range (max. 200 �C), since the plug connection is very close to the hot area.
Note
More info 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.
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