When The Instrument Developed FPGA Carry Chain Based Precision Measurement

Time-interval measurement has a huge influence in the speed test of warhead and fuse speed setting. And the high precision time-interval measuring device can assure that the results of the speed and fuse speed setting test are accurate and reliable. Therefore, based on the current situation in the study of time-interval measuring method and time-measuring instrument, the methods which use a fast carry chain has solved the problem of large-scale time delay and low precision calibration in FPGA. Capture module, rough-time measurement module, thin-time measurement module and encoder module are designed in the selected high-capacity FPGA as well as other function modules and realizing test and calibration methods based on FPGA carry chain.For improving efficiency of time measuring instrument, through a detailed analysis of the characteristic and accuracy of pulse counting method and carry chain delay line method, combining the rough-time measuring and thin-time measuring method was realized by structuring a carry chain delay line in FPGA. In the study of solving solutions for the delay line calibration and large latency problem, counting technical index of measuring instrument the designed instrument combined the two methods into the overall program. In order to complete the high-speed and reliable time measuring instrument for data processing and control while fully utilize the on-chip resources within the FPGA, prepared software programs based on the Nios â…¡ processor. After the development of the instrument, analysis of acquired data in the calibration measurement, obtain the exact delay time of the delay line and the nonlinear index of the delay unit. By using the phase-locked loop phase shift function on chip, the controllable time interval generator is made to evaluate the performance of time measure instrument.A large number of experiment results showed that this time measuring instrument can achieve the resolution with high accuracy of100ps in the range of1ms. This instrument also has characteristics like automatic calibration of delay line, high reliability, high speed of processing, and easy operation.