MS Windows定时器性能分析及在定时-计数系统设计中的应用

MS Windows timer performance analysis and its application in the design of a timer-counter system

通过对MSWindows定时器性能的测试和分析,利用多媒体定时器精度分布的特点,采用"合成定时-选择计数"方法获得预定精度定时,在放射测量定时-计数系统中应用。

Objectives: To study the performance of MS Windows multimedia timer (MMT) and design a nuclear timercounter system making use of MMT correction mechanism discovered in the study. Methods: MMT uses callback function to provide preset timing period(PTP). Times between consecutive callbacks(TBCC) were acquired by coding in the callback function and statistically analyzed. Based on the result, a timercounter scheme using combined timing and selective counting(CTSC) was proposed, where a longer timing period(LTP) was achieved by the combination of N shorter timing periods(STP) and the total counts of the LTP was attained by multiplying the summed counts of the K STP whose TBCC was within a preset precision with normalizing factor N/K. The CTSC scheme was applied in a onesoftwaretimer, dualhardwarecounter nuclear timercounter system and tested. Results: In MMT performance tests, PTP of 20ms, 200ms and 2000ms were used. The frequency distributions of TBCC were symmetric, with 51.6% ~57.0% of the TBCC equaling to the PTP, 67.0% ~ 70.1% within PTP±2ms and 86~109ms maximum deviation, revealing a correction mechanism in the MMT to achieve overall precision. In the nuclear timercounter system test, the LTP was 2s and the STP was 20ms with precision of 2ms. 30minute counting rate curves were plotted for the two counters, each counting a stable electric pulse series. Though the curves demonstrated slight counting rate variations, the system performance was stable and satisfactory. That the counting rate variations of the two counters were independent in time and direction was observed. Tests with nuclear pulses produced expected results. Conclusions: Though MMT was found not suitable for high precision timing, MMT based CTSC scheme achieved adequate timing precision for nuclear timercounter system by making use of the discovered MMT correction mechanism.