Pressure switches
Reliable switching behaviour and excellent repeatability thanks to pressure switches
Top repeatability thanks to pressure switches and pressostats
In many industrial processes, pressure switches monitor the pressure and control downstream devices according to customer-specific requirements. A pressure switch or pressostat actuates an electrical switching contact as soon as the pressure exceeds or falls below the specified limit value in the process. Depending on the requirements, pressure switches with mechanical or electronic switching contacts, with or without display and various setting options are used.
Mechanical pressure switches have no local display and no analogue output signal and stand for excellent repeat accuracy and reliable switching behaviour. They do not require a power supply at all and are therefore also used as a safety-relevant component because of their fail-safety.
The simple yet robust pressure switches are suitable for monitoring heating and ventilation systems, compressors, pressure chambers, pipe sections and tank levels as well as for hydraulic applications. They are also available in Ex versions for potentially explosive areas and in SIL-tested versions for safety-critical systems. Combined with diaphragm seals, these components are used in hygienic areas in the food or pharmaceutical industries.
TRI-MATIC's pressure switch range includes measuring ranges from -15...0.5 mbar to 0...600 bar, factory preset or user selectable switching points and repeatability of up to 1 %.
Pressure switches for hydraulic and pneumatic systems
How does a pressure switch work? A pressure switch converts a change in pressure into an electrical switching signal. On the pressure side, a diaphragm or piston absorbs the system pressure and acts against an adjustable spring preload. When the defined switching point is reached, a contact opens or closes, thereby triggering a control or alarm function. In hydraulic applications, pressure switches protect pumps, cylinders and valves from overload, whilst in pneumatics, for example, they monitor the operating pressure of compressors. TRI-MATIC supplies both mechanical pressure switches (FEMA and TRI-SWITCH series) and electronic variants such as the DS 200, which features programmable switching points and high long-term stability.
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FAQ
In a hydraulic system, the pressure switch is connected directly to the pressure line. A diaphragm or piston absorbs the oil pressure and pushes against a pre-tensioned spring. As soon as the set switching point is reached, the mechanism actuates an electrical contact (normally open, normally closed or changeover). This signal can switch off a pump, activate a valve or trigger an alarm. The hysteresis – that is, the difference between the on and off switching points – prevents unwanted chattering of the contact in the event of pressure fluctuations.
In many industrial processes, pressure switches monitor the pressure and control downstream devices according to customer-specific requirements. As soon as a preset pressure is reached, a pressure switch or pressostat opens or closes an electrical switching contact.
Pressure switches are used wherever a specific pressure value is required to trigger a switching action:
- Hydraulics – overload protection for pumps and cylinders, pressure limitation in presses
- Pneumatics – compressor control, monitoring of compressed air networks
- Water and cooling technology – flow monitoring in cooling circuits, dry-run protection
- Process engineering – pressure limitation and alarms in chemical or pharmaceutical plants, filter monitoring (using differential pressure switches).
The appropriate design depends on the medium, pressure range and required protection class. If you have any questions, the TRI-MATIC advisory service will be happy to help.
A mechanical pressure switch operates using a spring and a contact. The switching point is set via an adjusting screw. This design is tried and tested, cost-effective and requires no auxiliary power. An electronic pressure switch uses a pressure sensor (e.g. a thin-film sensor) and integrated electronics. The advantages:
- Programmable switching points – adjustable at the touch of a button or via IO-Link
- Wear-free operation – no mechanical contact, therefore virtually unlimited switching cycles
- Higher accuracy and long-term stability
- Optional analogue output (4–20 mA) in addition to the switching output
TRI-MATIC offers both variants: the mechanical FEMA series and TRI-SWITCH MINI, as well as the electronic models DS 200 and TRI-SENSOR SWITCH.
Hysteresis (also known as the switching differential) is the pressure difference between the make point and the break point. If the pressure rises to the upper switching point, the contact closes. However, it only switches back once the pressure has fallen by the hysteresis value. This deliberate difference prevents the pressure switch from constantly switching back and forth in response to small pressure fluctuations. In mechanical models, the hysteresis is determined by the design and is partly adjustable; in electronic pressure switches such as the DS 200, it can be freely programmed.
Pressure measurement from TRI-MATIC
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