Reference primary standards

Pressure balances are high precision fundamental pressure standards that define the derived unit of pressure directly from the fundamental units of mass, length and time following the formula p = F/A.

The direct measurement of the pressure with a pressure balance combined to the know-how of Desgranges & Huot guarantee the best metrological specifications on the market.

• High-quality piston-cylinder units (high floating time and long-term stability)
• Cast aluminium case and robust sub-assemblies (minimum maintenance and overhaul services)

The CPB6000DP is designed for differential pressure calibra-tion and high static line pressure and consists of dual liquid lubricated gas type pressure balances.

A CPB6000DP balance is the combination of two CPB6000-PX balances:

• Integrated into one common case to facilitate operation and improve measurement.
• Built-in pressure controls are provided
• One side of a CPB6000DP can also be used as a CPB6000-PX for gauge pressure calibrations

Application

The pressure balances of the series CPB6000 are applicable in a very wide variety of pressure calibration and measure-ment tasks. Appropriate configurations are available for use in primary standards laboratories and as reference instru-ments on the shop floor.

Operating principle

The CPB6000DP consists of two piston-cylinder units. One piston-cylinder unit measures the static pressure in the system and the other one measures the differential pressure. For measuring the differential pressure, a piston-cylinder system with a minor manufacturing tolerance and a high repeatability is required in order to achieve a low measurement uncertainty.

The test procedure is as follows: First the same static pressure is generated at both piston-cylinder systems. Next, as many fine increment masses are applied on the piston-cylinder system measuring the static pressure until both pistons are in their middle floating position. Following this, both piston-cylinder systems are isolated from each other, and the masses generating the differential pressure are applied on the second piston. Both systems are now maintained in their floating positions with the help of the volume slide.

This procedure compensates for any diaphragm movement of the test item generated by the pressure. The exceptional intrinsic characteristics of the piston cylinders make it possible to provide and maintain a static pressure with high precision. The stability of the static pressure is much better than the measurement uncertainty of each of the two cross-sectional areas of the pistons.

• Contingent error on the equilibrium between the comparison and measuring piston.
• This term is a function of the static pressure.
• Uncertainty on the effective area and masses on the piston-cylinder system.