| As the requirements of multi-channel, wide range and high precision of time-intervalmeasurement in many engineering applications, the precision multi-channel time-intervalmeasurement and range extension methods were studied, a precision multi-channeltime-interval measurement system was developed, and also made the system a error analysisand calibration, tested the performance of the system. The main work of this paper can besummarized as follows:Based on studying the principle of precise time-interval measurement, researched usesampling propagation delay state and pipeline pretreatment methods achieve multi-channelmeasurement. After analyzing the measuring principle of time to digital conversion chip, putforward a measuring scale expansion method, in time to digital conversion chip’s internal startretrigger mode, without additional hardware cost, use interrupt extend internal retrigger startnumber to extend measuring range.Under analyzing the function and performance of the system, got an overall design,divided the system into virtual instrument control unit, microprocessor control unit and timeinterval measurement unit, and also carried out profile design for each unit. On the basis ofanalyzing the function and performance of the system’s hardware, the microprocessor controlcircuit, the time interval measurement circuit and other hardware circuit was designed andimplemented. On the basis of analyzing the function and performance of the system’s software,the virtual instrument control software and the microprocessor firmware program was designedand implemented.On the basis of analyzing the measurement error sources, proposed3σ criteria to eliminategross error, using positive and negative testing method to calibrate system error, using timeinterval average method to optimize random error, the emphasis is the calibration of channels’time delay, after calibration, the deviation between channels is superior to90.45ps.After studying comparative and fixed time interval measuring methods, set up testplatforms to compare the accuracy and stability of the developed system and SR620counter,and tested the system’s measurement accuracy and stability of various channels for differentorder interval. Results show that the system is as accurate as SR620counter, but can bemeasuring with multiple channels, for nanosecond scale interval measurement, the accuracy canreach10.9ps, the stability (standard deviation) can achieve44.86ps, for microsecond level timeinterval measurement, the accuracy can reach14.8ps, the stability can be79.57ps, for millisecond magnitude interval measurement, the accuracy can reach17.0ps, the stability canbe81.56ps.Final results show that the developed time interval measurement system can be measuringfor8channel signals on the same time, the least significant bit (LSB) of each channel is81ps,the measurement resolution can be50ps, and the measurement range is100s. |
