by Michael Bair and Tim Francis
Fluid pressure is a derived measurand (N/m2) that is realized primarily through manometers and piston gauges at the NMI level. Piston gauges are becoming more useful as primary standards due to the ability to characterize the effective area, the most difficult variable to measure in a piston gauge, with enough confidence and low enough uncertainty to support the needs of an NMI or private laboratories with the need to resolve pressure at the highest level.
Fluke Calibration has introduced a piston gauge to be used as a primary standard to realize pressure in both gauge and absolute modes from 10 to 500 kPa called a PG9607. All variables in the pressure equation for a piston gauge were addressed in the design of the piston gauge to ensure the lowest uncertainty in pressure that could be attained.
This paper discusses the design of the piston gauge and the projected uncertainties than can be resolved with a fundamental characterization.