Pressure equalisers

Mechanical deadweight testers or primary standards are often the most accurate reference instruments for pressure measurement. Their working principle is based on the physical principle of pressure = force/surface area.
The mass pieces mounted on top of the piston-cylinder system are the source of a specific force. By creating a certain (opposite) pressure inside the pressure equalisers, equilibrium is achieved: pieces of the mass, including the freely moving piston in the piston-cylinder system, float, resulting in a very precise pressure at the test port.