1. Department of Electrical Engineering, Tsinghua University, Beijing 100084, China
2. National Institute of Metrology,Beijing 100029, China
3. The Key Laboratory for the Electrical Quantum Standard of SAMR, Beijing 100029, China
4. China Jiliang University, Hangzhou, Zhejiang 310018, China
Abstract：The joule balance method is a quantized definition of the unit of mass research programme, in which the flux linkage difference measurement is a core part during the measurement process of joule balance, and its basic principle is the integral measurement of coil induced voltage over time. The joule balance is a method independently proposed in China to realize the quantized definition of the unit of mass. The flux linkage difference measurement is a core part during the measurement process of joule balance, whose basic principle is the integral measurement of coil induced voltage over time. When the original flux linkage difference measurement method based on the digital integration principle is applied to the synchronous measurement process of joule balance, it is difficult to overcome the intrinsic weakness of the data acquisition card so that it cannot achieve the 10-8 magnitude of relative standard uncertainty. Therefore, a new method based on the dual-slope integration ADC is proposed to achieve the analog integral measurement. With the continuously analog integrating measurement characteristic of the dual-slope integration based ADC, the measurement error introduced by the level holding sampling process in the original method is eliminated. The measurement dead-zone introduced by ADC digital quantization is removed by the successive triggered measurement of multiple parallel ADCs. The measurement dispersion introduced by the accumulation of time-varying noise is suppressed by the time-shared noise zeroing of multiple ADCs. The test results show that after applying the above method in the synchronous measurement process, the relative standard uncertainty of flux linkage difference measurement is suppressed from 10-6 to 1.7×10-8.
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2021, Vol. 42 
