Differential pressure switch for monitoring filters, fans, or air flow in air conditioning and ventilation systems, tested according to the EU Gas Appliance Directive EU/2016/426 and DIN EN 1854
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The FD series is designed according to the special guidelines for liquefied gas technology. All parts in contact with the medium are made of stainless steel 1.4104 and 1.4571.
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This universal pressure switch can be used in general mechanical engineering and the printing machine industry, as well as in pneumatics and hydraulics. SIL 2 according IEC 61508-2
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Pressure switches of the DNS series are suitable for monitoring and controlling pressures in chemical plants, process engineering and any situation where the pressure of aggressive liquids and gases must be monitored. All components of the sensor system are made of highquality stainless steel (1.4571) and welded using the latest methods without filler metals. The pressure sensor is gasket free plasma welded. SIL 2 according IEC 61508-2
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Chemical version (switching housing with surface protection) Pressure switches of the DNS series are suitable for monitoring and controlling pressures in chemical plants, process engineering and any situation where the pressure of aggressive liquids and gases must be monitored. All components of the sensor system are made from highquality stainless steel (1.4571) and welded using the latest methods without filler metals. The pressure sensor is gasket free plasma welded. SIL 2 according IEC 61508-2
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FEMA negative pressure switches detect the pressure difference relative to atmospheric pressure. All data relating to the switching pressure ranges and thus also the scale divisions on the switching devices are to be understood as the difference in pressure between the relevant atmospheric pressure and the set switching pressure. The "zero" reference point on the scale of the unit corresponds to the relevant atmospheric pressure.
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FEMA differential pressure monitors are suitable for monitoring and controlling differential pressures, flow monitoring and automatic control of filter systems. A double chamber system with stainless steel bellows or Perbunan diaphragm detects the difference between the two applied pressures.
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Differential pressure, vacuum and overpressure switches suitable for monitoring neutral and slightly aggressive liquids and non-flammable gases. It can be used as a flow switch fitted across an orifice plate.
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Pressure Switches for Liquids & Gases – Safe Switching, Precise Monitoring
Mechanical pressure switches for liquids and gases switch reliably when thresholds are exceeded or not reached. Depending on the design, a diaphragm or piston actuates a microswitch (NO/NC/SPDT). Typical applications include hydraulics/pneumatics, pump & compressor control, pipeline/filter monitoring, as well as plant and building services.
Available with adjustable hysteresis, high IP ratings (up to IP67/69K), optional ATEX/IECEx approvals and media-resistant materials (e.g., stainless steel 316L, special alloys). ICS Schneider Messtechnik supports you with selection, sizing, material/seal choice, installation and documentation.
FAQ on Pressure Switches for Liquids & Gases
Answers on selection, switching range, hysteresis, media compatibility, IP/Ex ratings, connections, installation and maintenance.
Which media are these pressure switches suitable for?
| Media | Recommended design | Note |
|---|---|---|
| Hydraulic oil / water | Diaphragm/piston, brass or 316L | Use snubber/restrictor with pulsation |
| Compressed air / inert gases | Diaphragm version | Drain moisture/condensate |
| Aggressive media | Stainless steel 316L / special alloys | Select seals per media (FKM/EPDM/PTFE) |
How do I choose the correct switching range?
As a rule of thumb, select 1.3–2.0 × the working pressure. For spikes, size larger or add a snubber.
What is hysteresis and why is it important?
Hysteresis is the distance between the switch-on and switch-off points. It prevents chatter and increases service life. Many models offer adjustable hysteresis.
Which electrical contact variants are available?
| Contact | Designation | Use |
|---|---|---|
| Normally open | NO | Start/stop signals |
| Normally closed | NC | Safety/fault indication |
| Changeover | SPDT | Flexible switching applications |
What process connections are common?
| Connection | Standard | Typical application |
|---|---|---|
| G 1/4, G 1/2 | ISO 228 | General industry |
| ¼″ NPT, ½″ NPT | ASME | US / oil & gas |
| Hygienic (e.g., Tri-Clamp) | DIN/ASME | Food/pharma (often with diaphragm seal) |
What IP ratings and approvals are available?
Typically IP54–IP67/69K. For hazardous areas, variants with ATEX/IECEx (e.g., Ex ia/ib) are available.
How do I protect the switch against pressure spikes and vibration?
Use snubbers/restrictors, capillaries, or remote mounting. Mechanically decoupled installation increases lifetime.
Are there special requirements for high medium temperatures?
Yes. Use a siphon/cooling element; check materials and seals for temperature resistance. For steam, add proper thermal decoupling.
How is the switching point set?
Via adjusting screw (spring preload). After adjustment, verify with a reference pressure and document as-found/as-left.
What are typical applications?
- Pump/compressor control (min/max pressure)
- Pipeline/filter monitoring (Δp, clogging)
- Hydraulics/pneumatics (limits, protection)
- HVAC/building services (room/duct pressure)
What maintenance and test intervals are recommended?
As a guideline annually; for safety-critical applications semi-annually. Perform visual checks (leaks, cables), functional and leak tests.
Do you support selection and commissioning?
Yes. We advise on range & hysteresis, materials/seals, EMC/IP, provide documentation, and support installation/acceptance.