Mechanical standards for measuring gas pressure up to 7 MPa based on a piston–cylinder system are known with relative uncertainties on the order of 1 ppm (ref. 1). The challenges in an experimental realization lie in determining the effective area of special pressure balances and in accounting for the pressure distortion. Comparisons of the mechanical pressure standard with independent methods to exclude sources of systematic uncertainty are currently available only around 0.1 MPa at the required uncertainty levels. Here, such an independent cross-check is performed up to 7 MPa based on electrical measurements of helium gas. Enabled by recent progress in ab initio calculations, pressure can be accessed through measurement of the dielectric constant. By using theoretical values for the polarizability and the virial coefficients of helium, the change in capacitance and hence the pressure can be determined up to 7 MPa. The relative uncertainty of this method is below 5 ppm and can serve as a new primary pressure standard complementary to the mechanical pressure standard. This answers the long-standing question whether a pressure standard based on capacitance measurements could be devised2.
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The complete dataset of Fig. 2 is listed. The first six columns contain the left part of the figure and columns 10–16 contain the right part. Each column has an individual header further specifying the content.
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Gaiser, C., Fellmuth, B. & Sabuga, W. Primary gas-pressure standard from electrical measurements and thermophysical ab initio calculations. Nat. Phys. 16, 177–180 (2020). https://doi.org/10.1038/s41567-019-0722-2