Technical Blog

What is a Differential Pressure Switch?

Differential pressure switches are part of our product portfolio, but what is a differential pressure switch?

A differential pressure switch is an electro-mechanical device which is used for sensing a difference in pressure between two points.

How does a Differential Pressure Switch work?

When connected to two pressure sources, the differential pressure switch can be used as an alarm to make or break a circuit as the pressure rises or falls beyond the preset value. The internal diaphragm within the differential pressure switch deflects under pressure to make the contact; this could be either a SPST or SPDT contact. The set point can be factory preset or field adjustable.

Differential pressure switches tend to be used for energy saving or preventative maintenance, for example; monitoring air filters for blockages. As the filter clogs or blocks up, the pressure on the high side will rise and once at the activation point, the pressure switch will change state.

The diagram below shows this application in action.

Applications for Differential Pressure Switches

Some of the more common applications for differential pressure switches are;


  • Air proving
  • Fans
  • Ventilation flow
  • Air filter health/status
  • Exhaust ducts
  • Cleaning and purification
  • Dirt and dust filter loading
  • Combustion exhaust venting
  • Exhaust/flue airflow blockage
  • Flue gas
  • Air conditioners
  • Heating/venting blower fan
  • Gas pressure


Differential Pressure Switches from Variohm

Differential pressure switches are part of our pressure switches range and can be viewed on our website. They are from our supplier DesignFlex who are part of the World Magnetics Group.

We have differential pressure switches that will activate from as low as 7Pa, our range has both SPDT and SPST contacts available.

The PSF102 differential pressure switch which is featured in the drawing above comes with many standard ports and mounting options. It has a dependable long life and gold contact points. It offers high resolution and high accuracy field adjustments. See the data sheet for the PSF102 Differential Pressure Switch for full product details. 

Article published on: 28/03/2017