Differential Pressure Gauges

Differential pressure gauges are precision instruments designed to measure the pressure difference between two separate process points. Unlike standard pressure gauges that reference atmospheric pressure, differential pressure gauges connect to two process ports simultaneously — a high-pressure inlet and a low-pressure inlet — and display the net difference between them. This makes them indispensable in applications where the relationship between two pressures carries critical process information, such as determining filter condition, calculating flow rate, or inferring liquid level in a closed vessel.

The sensing element at the heart of a differential pressure gauge is typically either a capsule or a piston type. In capsule designs, two flexible metallic diaphragms are welded together to form a sealed chamber; the pressure difference across the capsule causes a proportional deflection that is transmitted mechanically to the pointer. Piston-type sensing elements use a spring-loaded piston that moves in response to the differential pressure, offering robust performance in higher-pressure or more demanding process environments. Both designs translate the mechanical displacement into a clear, readable dial indication.

Differential pressure gauges serve a wide range of industrial applications. In filter condition monitoring, they are installed across filter housings to indicate the pressure drop caused by particulate build-up; a rising reading signals that the filter element requires cleaning or replacement. In flow measurement, they are paired with primary elements such as orifice plates, venturi tubes, or flow nozzles — the differential pressure generated across the restriction is directly proportional to the square of the flow rate, enabling accurate flow indication without powered instrumentation. For liquid level measurement in closed or pressurised vessels, the gauge is connected between the bottom and top of the vessel, with the differential reading corresponding to the hydrostatic head of the liquid column.

Construction options are available to suit a broad spectrum of process conditions. Body materials include stainless steel for corrosive or hygienic environments and cast iron for general industrial service. For applications subject to vibration, pulsation, or rapid pressure fluctuations, a glycerin-filled dampening option is available; the viscous fill fluid cushions pointer movement and significantly extends service life. Process connections are offered in both top-entry and side-entry configurations, providing installation flexibility across different pipework layouts and panel-mounting arrangements.

Scale options cover the full range of common differential pressure units, including millibar (mbar), bar, and kilopascal (kPa), with ranges selected to match the specific application requirements. Standard dial sizes of 100 mm provide clear readability in most industrial settings. Accuracy is typically ±1.6% of full scale, conforming to EN 837 or equivalent standards. The combination of robust construction, flexible configuration options, and reliable sensing technology makes these gauges a versatile and cost-effective solution for differential pressure measurement across process, utilities, and HVAC industries.