How do mechanical and electronic pressure switches work?
Mechanical pressure switches
A mechanical pressure switch converts fluid pressure into a mechanical movement that actuates a mechanical switch contact within the pressure switch device. The switch will have a pre-set or configurable mechanical adjustment of the switch point. A mechanical pressure switch will provide an electrical switch output signal whenever the switch is actuated without requiring any power supply.
Mechanical pressure switches are generally simple devices, either intended for low cost applications or built for reliability, depending on how often the switch signal has to be transmitted. Switches are designed either for low demand mode (very few switching cycles e.g. in safety applications) or high demand mode (frequent switching cycles e.g. in process control).
The hysteresis is usually not adjustable, thus the reset point for switching cannot be configured and is pre-set by factory setup. Mechanical pressure switches are often used to switch high currents, such as pumps and drives. However, mechanical contacts often face problems with switching very low voltage in PLCs and modern electronics unless more expensive gold-coated contacts are used.
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Electronic pressure switches
An electronic pressure switch provides electronic switch output signals, and very often produces an additional analogue output signal proportional to the pressure. Electronic switches are either factory programmed to the desired switch points or provide a programming interface by integrated display and buttons. They have an integrated programmable logic, which allows to adjust the switch points and output signal to the application specific needs.
Delay time, switch point, reset switch point, hysteresis or window function, normally closed or normally open, and many more functions can be programmed in modern electronic pressure switches. The local indication also provides a constant pressure reading and indicates if the switch outputs are active or not. Modern technologies, such as the use of IO-Link allows remote programming via the signal cable.
In the second part of this article you will soon find a recommendation when to use a mechanical or an electronic pressure switch. If you need any help in selecting an appropriate switching solution for your pressure, temperature or level measurement, your contact person will gladly be of assistance.
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