Developed Fpga-based High-precision Chronometer

High precision time-interval measurement plays a great role in fragment velocity measuring, blasting network and muzzle fuze velocity loading. Traditional time-measuring instruments cannot satisfy the requirements of modern high precision time-interval measurement due to lower measurement accuracy and resolution. According to this, after introducing the present research status of high precision time-interval measurement methods and time-measuring instruments in detail, a time measurement method based on phase modulation was put forward and time-measuring instrument was developed.Combined with pulse counting method, the paper stated measuring principle of phase modulation method, analyzed its measurement accuracy and demonstrated technical indexes, overall plan of time-measuring instrument. Basic components such as LM324 and LM339 were used to design signal regulate circuit, so that targets signals could be converted into square wave pulse with 3.3V amplitude and steep edge. In order to realize time-interval detection and measurement, Cyclonelll EP3C16Q240 FPGA from was chosen to build hardware circuit, including start and stop signal integration, multi-phase clock generation. MSP430F149 single chip was chosen as timing control and data processing unit, avoiding level change between FPGA and single chip, reducing the instrument consumption. At the same time, single chip calculated the count value to get time-interval result. Digital tubes driven by MAX7219 were used for display circuit, so that time-measuring instrument could expand its expansion conveniently; Use precise programmable pulse generating circuit to test the performance indexes of the instrument, and compared its results with pulse counting method. The test results shown that without raising the crystal frequency, the instrument has realized the resolution of 250ps with characteristics of high accuracy, high speed, simple structure, low cost and so on.