Diaphragm Gauges ASME Grade A-1% Accuracy

Marsh low-pressure diaphragm gauges are universally known for their dependable performance and accuracy, with ASME Grade A-1% accuracy for ranges above 30″ of water.

Available ranges include vacuum and pressure in inches of water, ounces per square inch and millimeters of mercury.  The units incorporate a unique bronze diaphragm element and solid safecase design, allowing for accurate low-pressure readings in support of a variety of applications.

How Marsh diaphragm gauges work:

Diaphragm gauges are sensitive instruments used in low-pressure applications typically not exceeding 10 psi. The diaphragm capsule is an elastic metal sensing element comprised of two thin wall diaphragms whose sides are soldered together to make the capsule. Whenever air or gas enters the intake port (gauge connection), it travels into the diaphragm capsule. As vacuum or pressure is applied to the diaphragm capsule, the walls of the capsule expand and contract in response to the change in pressure. This change is then transferred to a rotation rod and arm that rest on the outside of the capsule. The rotation rod is connected to a geared movement through a linkage system. Connected to a shaft, this system then drives the pointer over a dial marked in appropriate pressure or vacuum units for repeatable, high-precision accuracy.



  • Unique bronze diaphragm element design
  • ASME Grade A-1% accuracy above 30″ of water

Available ranges include:

  • Vacuum and pressure in inches of water
  • Ounces per square inc
  • Millimeters of mercury


  • ¬†HVAC systems
  • Low-pressure gas burner systems
  • Any OEM or industrial application where low pressure measurements to a high degree of accuracy are required