The calculable cross-capacitor laboratory is responsible for the establishment and maintenance of the primary standard of capacitance unit in the electromagnetic metrology.
In 2017, NIM’s new vertical calculable cross-capacitor with a movable guard electrode applying electrical compensation approach was established. Its standard uncertainty to reproduce the Farad of capacitance unit is 1.0×10-8, which achieved a new capability to reproduce capacitance unit against all other similar apparatuses in the world. Adopting this new calculable cross-capacitor, NIM participated in the key comparison of 10 pF capacitance standards and 100 pF capacitance standards (CCEM.K4-2017) with the pilot lab of BIPM and other 6 NMIs including METAS, NIST, NMIA, NPL, PTB and VNIIM. The final comparison report was published in BIPM KCDB in 2018, it shows that NIM’s comparison results for 10 pF and 100 pF capacitance achieved a good agreement with KCRV (key comparison recommended value), which obtains the international mutual recognition.