PRESSURE ONLINE H LOGO.png

บทความ เกจวัดแรงดัน

Temperature switches in machine building: Which kind suits?

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. Depending on 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 electronic switch. With this particular instrument, you can 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 therefore continuous temperature monitoring aswell.
Furthermore, switches of this 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 may 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, typically,150 �C, that is sufficient in most of applications, however. As a way to fulfil their tasks, electronic temperature switches need, in addition to a power source, yet another contactor since their transistor only switches suprisingly low power.
digital pressure gauge 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 employed for industrial applications. They cover ? depending on the version ? temperatures up to 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 is not 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.
Regarding price and performance, the switch solution described here is positioned 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 wide range of applications. These instruments may also switch with low voltages up to 250 VAC, sufficient reason for this they can 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 limited temperature range (max. 200 �C), since the plug connection is quite near 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 can be found on the WIKA website.
Also read our articles
Overview: So how exactly does the IO-Link work?
Safety temperature limiter for plants safe to use

Recent posts