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Capacitive grating sensor can be used to measure the length, as its capacitance changes with the shift difference. There are several measuring systems consisting of capacitive sensor, but all their basic principles are capacitive differential sensing. The structure, principles and characteristics of capacitive sensors are introduced in this paper. Especially, we designed a high-resolution electronic length measuring system based on Capacitive Grating Sensor. And the measurement error of the system and the reason are analysed. For this system, the measuring range is from 0 to 500mm, the resolution is 1um, the indication error is 5um, the measuring speed is 1m/s. Accurate measurement on account of large displacement is achieved with the system.

A photoelectric hybrid coupling current transformer has a lot of obvious advantages over a traditional electromagnetic current transformer. It is very valuable in practical application for the electricity protection and signal measurement of power system. This paper will introduce the design of a new type of Rogowski coil, integral and filter circuit, the realization of A / D timing and Manchester decoding with CPLD. The test results have proven that the proposed system design can perform the expected functionality of photoelectric coupling current transformer. It can better meet the power system’s requirements in the high-speed data processing, large data quantity and complex operation. It also has merit of being simple in structure and easier for modification. It is worth of further investigation.