Primary standards

Highest accuracy with Primary Standards from WIKA

Primary standards (often also referred to as mechanical dead-weight testers, pressure balances or primary pressure standards) are the most accurate reference instruments for pressure. Their functional principle is based on the physical principle of pressure = force/area. Mass pieces placed on the top of a piston-cylinder system are the source of a precisely defined force. By producing a certain (counter) pressure inside the primary standard an equilibrium is achieved: the mass pieces, including the free-running piston of the piston-cylinder system, are floating, which will lead to a very accurate pressure at the test port.

How Does a Deadweight Tester Work?

In a deadweight tester, the force is supplied by a mass in a gravitational field on top of a piston with a specific cross-sectional area that rotates within a cylinder. This piston cylinder system is manufactured to very tight tolerances for smooth, precision operation. The fluid (pneumatic or hydraulic) under the piston is pressurized so the piston and mass “float” in equilibrium. The pressure in the fluid is equal to the force exerted by the mass over the cross sectional area of the piston.

What is a Primary Reference Pressure Standard?

It's the primary instrument you are using as a reference to measure pressure in a standard way. They usually refer to instruments such as deadweight testers, pressure balances and piston gauges, which are traceable to SI units. Using any of these devices is essential to a fully equipped pressure calibration lab.


What is the Kn factor?

All piston-cylinder units and masses that can be mounted on Desgranges & Huot pressure balances are built around the nominal mass-to-pressure conversion coefficient Kn, named after the Danish physicist Martin Knudsen. The nominal effective area ...