Low gauge pressure comparisons between MIKES, Metrosert and FORCE Technology Range -2000 Pa to +2000 Pa: Report on EUROMET Project 921

MIKES (FI), Metrosert (EE) and FORCE Technology (DK) compared their low gauge pressures in 2006. The reference standards of the three laboratories for low gauge pressures apply dissimilar operating principles: a digital piston manometer at MIKES, a water column manometer at Metrosert and a diving bell-type standard at FORCE Technology. The comparison covered the range from -2000 Pa to +2000 Pa. The transfer standard was a Furness FCO510 micro-manometer. The stability of the transfer standard was not as good as expected. The results of MIKES and Metrosert were in a good agreement except at nominal pressures -20 Pa and +20 Pa where the absolute values for the normalised error En were slightly higher than 1. The uncertainties given for the Metrosert results at these nominal pressures were much lower than the accredited uncertainties at present. The results of MIKES and FORCE Technology in the range from -200 Pa to +200 Pa were in a good agreement, using the uncertainties given in the CMC tables. The results outside this range could not be assessed due to the instability of the transfer standard.