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New primary method for the measurement of pressure developed


Scientists from PTB have implemented a novel method for pressure measurement – quasi as a byproduct of the work on the "new" kelvin – and have reported about it in Nature Physics. The method is based on measuring the density of the measuring gas helium by means of a capacitance measurement. The degree to which gas between the electrodes changes the capacitance of a highly stable, special capacitator is measured. As this method only refers to one universal property of helium gas, which is expressed via the dielectric constant, it is a primary method.

One of the newly developed high-precision pressure balances

For the first time in practice, PTB has thus succeeded in realizing a groundbreaking theoretical approach which had already been formulated by Mike Moldover of NIST (the U.S. national metrology institute) as early as 1998.

The new pressure measurement method can be used to check the most accurate pressure gauges, for which PTB is known as the world leader. Checking such instruments was formerly possible in the range of up to 100 000 pascals only; now 7 million pascals are feasible. A comparison between mechanical and electrical pressure measurements has thus been carried out for the first time with a relative uncertainty of less than 5&nbsp:· 10−6