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Pressure Balance High-Pressure GB

CPB 5000 HP

WIKA Operating Instructions Pressure Balance High-Pressure Version 2.3

2.3.2 Temperature (Piston/Cylinder) .

The effective cross-sectional surface of the piston/cylinder system depends on the temperature.

The effect depends on the material used and is described by the temperature coefficient (TK).

In the event of deviations from standard reference conditions (typically 20°C), the following formula

must be used to make a correction:

()()

TKtt

pressureTrue

ferenceAppl

⋅−+

⋅=

valueNominal

Example:

Reference temperature: 20°C

Temperature during use: 23°C

TK: 0.0022%

()

barbarpressureTrue 99340.99

2.220231

100

⋅−+

⋅=

−

Without the correction, measurements would all be "off" by 0.007 %.

2.3.3 Ambient conditions .

The effects of ambient conditions

 air pressure

 room temperature

 relative humidity

should always be taken into consideration if the highest level of accuracy is required.

Fluctuations in ambient conditions change air density.

The air density affects the pressure through the buoyancy of the weights:

⎟

⎠

⎞

⎜

⎝

⎛

−⋅=

densityWeight

densityAir

Weight 1 weightNominal

The air density is typically 1.2 kg/m

The density of the weights (non-magnetic steel) is 7900 kg/m

A fluctuation of 5% in the relative humidity causes an additional uncertainty in the measurement of

about 0.001%.

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