Differential Gauges and Switches

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Filtertechnik are proud to be an official distributor of US-made Differential Pressure Plus products. Differential Pressure Plus Inc. has been designing and manufacturing differential pressure switches, gauges and status indicators in Branford, CT, since 1991. The vast majority of applications involve water and fuel filtration, however, differential pressure gauges can also be used in applications such as:

  • Liquid levels in tanks.
  • Monitoring of flow rates.
  • Balancing valves.
  • Monitoring pump life and performance.
  • Monitoring scale/sediment buildup in heat exchangers and other critical equipment.
  • Leak detection.

Differential pressure is one of the most adaptable, yet underused tools in the industry and we want to change that.

The product range can be split into two groups, low cost differential indicators and precision differential gauges. The precision range of units can be supplied as a switch only, a gauge only or a gauge and switch combined.

Differential pressure measurement can be achieved by two different methods, diaphragm and piston. Below is a quick guide to the pros and cons of each method.


These gauges measure pressure drops using a precision machined metal piston encapsulated in a PTFE seal. This creates a similar seal to a hypodermic needle. Despite the accuracy to which these seals are machined, there is still a small amount of leakage that occurs around the piston. This is why a piston gauge should not be used for liquid level applications or leak detection systems. Instead, they are recommended for filtration systems and flow rate applications.

Advantages of Piston Gauges

  • Lower costs
  • Higher temperature capabilities
  • Higher-pressure ratings
  • Higher differential pressure ranges


This type of gauge utilizes a rubber diaphragm to measure pressure. This creates a perfect barrier through the gauge and allows for zero leakage. Because they create a perfect seal, they are best suited for liquid level applications and leak detection systems. As the diaphragm size increases, the sensing area also increases. This is why larger diaphragms are used on low pressure ranges, such as in the 400 DGC unit.

Advantages of Diaphragm Gauges

  • No flow through the gauge
  • More sensitive measurement
  • Lower pressure ranges available
  • Can have a zero centre dial
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