Temperature switches in machine building: Which kind suits?

Super are employed in machine building along with 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 switch on a fan for cooling. According to 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 particular instrument, it is possible to change the limit values yourself and set several switch points. Electronic temperature switches can be utilized 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 this type could be fitted with digital communication (IO-Link). The advantages 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, normally,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 is the wide temperature range. Generally, expansion thermometers are employed for industrial applications. They cover ? with respect to the version ? temperatures around 400�C.
This instrument type offers the operator the chance 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 is not needed. Dial thermometers with switch contacts function without additional power supply and, furthermore, offer an on-site display. A further processing of the signal is not possible, however.
Regarding 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 are very compact, cost-effective and 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 provide 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), since 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 our articles
Overview: So how exactly does the IO-Link work?
Safety temperature limiter for plants safe to operate

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