To meet the high precision requirements of time interval measurement of signal processing system for time grating sensors

a signal processing system based on TDC-GP21 chip is proposed. FPGA is used to control high precision measurement pattern of TDC chip to count integer part of time pulse

and the decimal part of time pulse can be measured precisely using gating circuit delay. In this way

time value is measured more precisely and the measuring resolution of the time grating sensors is improved; calibration measurements are employed to compensate the measurement results

thus the measuring errors are reduced. The experimental results show that the original measurement precision of the time grating sensors with 72 pairs of poles reaches

± 1″ and the resolution is enhanced to 0. 036″ at range of 0°

360°.