The Development Of Magnetic Modulator Based AC And DC Current Comparator

Precision current measurement is one of the foundation and core issues in the field ofelectromagnetic measurement. As a high accuracy ratio device, current comparator playsan extremely important role in current measurement. Existing current comparator can onlybe used to complete AC or DC measurement and hardly to meet the growing measurementrequirements. Therefore, the development of magnetic modulation based currentcomparator which can acopmlish either AC or DC measurement has strong theoretical andpractical significance.After analysing the basic principle of magnetic modulator and current comparator,three-line method and the Fourier series expansion are applied to give the sensitivityformulas of current comparator. A new kind of magnetic modulation based AC and DCcurrent comparator has been given, and the magnetic modulator, power amplifier, specialincentive source and differential demodulation circuit have been researched in detail. Theprototype of designed current comparator has been completed.The inherent and outside noise caused by the affiliated circuit have been discussed,and the magnetic and capacitive errors of the current comparator have also been analyzed.After that, the method of reducing the noise and error of the magnetic modulation currentcomparator have been given.Virtual instrument system has been designed to test the performance of the designedcurrent comparator. The measurement results show that DC linear error of the currentcomparator is about1×10-4, standard measurement uncertainty is better than2×10-5, thebandwidth of alternating measurement is no less than100kHz.