Progress on flux measurement with Josephson system at NIM

A new record of magnetic flux measurement of 1 Wb with the type A uncertainty of less than 1 ppm was presented, which is an improvement over the result that was achieved with our previous magnetic flux measurement circuit with Josephson system. The flux difference measured between the rectangular pulse synthesized with the Josephson system and the flux under test (around 1 Wb) is less than 4 mWb, which significantly reduces the impact of the flux meter reading error on the measurement results.