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.

已知基于活塞-汽缸系统测量最高7 MPa气压的机械标准，其相对不确定度约为1 ppm（参考文献^1）。）。实验实现中的挑战在于确定特殊压力平衡的有效区域并考虑压力畸变。目前，在所需的不确定度水平下，只有约0.1 MPa的机械压力标准与采用独立方法进行比较以排除系统不确定性的来源。在此，基于氦气的电学测量，进行高达7 MPa的这种独立的交叉检查。通过从头算的最新进展，可以通过测量介电常数来获得压力。通过使用氦的极化率和维里系数的理论值，可以确定电容的变化，从而可以确定最高7 MPa的压力。此方法的相对不确定度低于5 ppm，并且可以用作与机械压力标准互补的新的主压力标准。这回答了一个长期存在的问题，即是否可以制定基于电容测量的压力标准²。