# NMI – Calibration of pressure measurement #SWI2006

In pressure measurement the value of pressure is determined by dividing the force

exterted on a piston by the effective area of the piston. The effective area of the piston

may differ from the actual area because of irregularities at the piston edge and because of

leakage through the thin cavity between the piston and the enclosing cylinder. The

associated uncertainties constitute the largest contribution to the overall pressure

measurement uncertainty.

The various metrological institutes each use a different method of calculation of the

effective piston area for a given piston-cylinder combination. The figure below shows the

results of a comparison study in which six sets of measurement data were given to each

of the six participating institutes (taken from doi:10.1088/0026-1394/42/6/S11).

The details of these methods of calculation can also be found in same reference.

The question for the Study Group Mathematics with Industry 2006 is

Can we compare the different methods of calculation? Which is best?

Can they be improved any further?