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PressCal Software - Compare with Calibration Certificate

Some users note that the effective area shown on the deadweight tester's calibration certificate is different than that shown in PressCal. That is correct because the effective area on the calibration certificate is at 23 degrees Celsius, and in PressCal it is at 20 degrees C. That explains the difference in effective area.

The below images show how to compare calibration certificate results to PressCal calculations. See the link at the bottom of this article to view/download the same text and images in a pdf file.


Piston cylinder information in the calibration certificate
Effective area at 23 degrees Celsius and zero pressure


Piston cylinder information in PressCal
Effective area at 20 degrees Celsius and zero pressure

Thermal Expansion on the calibration certificate of 1.10E-05 is split in PressCal for the piston and the cylinder, and each are 5.5E-06.

Surface Tension on the calibration certificate is given in the resulting mass value. PressCal calculates this from the diameter of the piston-cylinder. Buoyancy and head correction values are different for similar reasons.


Pressure verification list in the calibration certificate

Pressure verification in PressCal at 6000 psi

The difference is 0.030023 psi, or 0.00009 % of reading, or 0.9 ppm. This is 88 times less than the measurement uncertainty specification of a 0.008% of reading (80 ppm) deadweight tester so the difference is negligible.


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