作者：王安然¹, 蒋延付², 郑博文³, 赵伟国¹, 黄峰¹, 沈平平¹

作者单位：1. 中国计量大学计量测试工程学院，浙江 杭州 310018;
2. 杭州山科智能科技股份有限公司，浙江 杭州 311121;
3. 台州市计量设备技术校准中心，浙江 台州 318000

关键词：超声波流量计;电容积分法;时间脉宽转换;周期偏差

摘要：

针对传统超声时差法在飞行时间测量中存在的问题，提出一种基于电容积分的间接飞行时间测量方法。该方法同步产生激励信号和参考信号，对参考信号和整形的超声回波信号比较后得到对应占空比的脉冲信号，采用恒流源积分电路得到稳定的电压，再通过AD转换获得飞行时间。为解决信号周期偏差对飞行时间测量的影响，设计脉宽调制和移相电路，并通过校正电路的设计，避免小流量测量出现较大的误差。然后，对设计的电路进行仿真，验证对信号周期偏差问题的解决。最终电路应用于超声波流量计样机的测量误差优于1%及重复性优于0.2%。

A transit-time measurement method for time difference ultrasonic flowmeter based on capacitance integration
WANG Anran¹, JIANG Yanfu², ZHENG Bowen³, ZHAO Weiguo¹, HUANG Feng¹, SHEN Pingping¹
1. College of Metrology and Measurement Engineering, China Jiliang University, Hangzhou 310018, China;
2. Hangzhou Seck Intelligent Technology Co., Ltd., Hangzhou 311121, China;
3. Taizhou Measuring Equipment Technology Calibration Center, Taizhou 318000, China
Abstract: In order to solve the problems of traditional ultrasonic time difference method in flight time measurement, an indirect measurement method based on capacitance integration is proposed. In this method, the excitation signal and the reference signal are generated synchronously. After comparing the reference signal and the shaped ultrasonic echo signal, the pulse signal of the duty information is produced. The stable voltage is obtained by using the integration circuit of constant current source and the flight time is calculated by AD conversion result. The pulse width modulation method and phase-shifting circuits are designed to solve the influence of signal period deviation on the measurement of flight time. The correction circuit is designed to reduce the large error in the small flow measurement. Then, the circuit is simulated to verify the signal period deviation. Finally, the experimental results of the circuit show that the measurement error is better than 1% and the repeatability is better than 0.2%.
Keywords: ultrasonic flowmeter;capacitance integration method;time to pulse width conversion;period deviation
2021, 47(8):44-50  收稿日期: 2020-10-29;收到修改稿日期: 2020-11-23
基金项目:
作者简介: 王安然(1996-),女,浙江金华市人,硕士研究生,专业方向为流量计量测试和智能化仪表
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