摘 要

随着科技的发展，工业的自动化程度愈来愈高，流量的测量也越加重要。不论是对石油、天然气管道内流量的检测，还是食品加工过程中饮料的灌装，都需要用到流量计。现在最主流的流量计就是超声波流量计了，它的实用性很高，在测量液体流量时，可以不用接触式被测的液体。这样不仅减少了探测装置接触液面对流体流速的影响，还有利于对危险的液体如酸、可燃气体、可燃液体的测量。其次，便于安装与拆卸，可以将探测装置安装在管道外侧，简单快捷，成本较低。最后利用高强度的超声波，超声波流量计可以对河流等大型场所进行测量。

本论文的课题是的是时差法超声波液体流量计设计。设计内容是通过单片机控制超声波换能器，来测量超声波在被测液体中转播的时间逆流与顺流的时间差，在根据时间差被与测液体流速的关系式求出被测液体的流速，最后再得到流量。

本文详细说明了超声波的特点，以及为什么用超声波来检测液体流量的原因。最后在查找了时差法原理和单片机程序的基础上，设计了时差法超声波液体流量计。本文设计的流量计主要用于常温（20℃）下圆形管道内各种清洁液体流量的检测，通过修改超声波在被测介质中的传播速度参数可以改变流量计的测量对象。

关键词：超声波，时差法，流量计，单片机

Abstract:

With the development of science and technology, the automation degree of industry is getting higher and higher, and the flow measurement is becoming more and more important. Flowmeter is used in the detection of flow rate in oil and gas pipelines and in the filling of beverages in food processing. Now the most mainstream flowmeter is the ultrasonic flowmeter, which has a high practicability. When measuring the flow of liquid, it can be used without touching the measured liquid. This not only reduces the influence of the liquid surface on the velocity of fluid flow, but also facilitates the measurement of dangerous liquids such as acid, flammable gas and flammable liquid. Secondly, it is easy to install and disassemble. The detection device can be installed on the outside of the pipeline, which is simple, fast and low cost. Finally, using high-intensity ultrasound, the ultrasonic flowmeter can measure large places such as rivers.

The topic of this paper is the design of ultrasonic liquid flowmeter based on time difference method. The design content is to measure the time difference between countercurrent and downstream when the ultrasound is transmitted in the measured liquid by controlling the ultrasonic transducer with a single chip computer. The velocity of the measured liquid can be calculated according to the relationship between the time difference and the velocity of the measured liquid, and then the flow rate can be obtained.

In this paper, the characteristics of ultrasonic wave and the reason why ultrasonic wave is used to detect liquid flow are described in detail. Finally, based on the principle of time difference method and the program of single chip computer, an ultrasonic liquid flowmeter with time difference method is designed. The flowmeter designed in this paper is mainly used to measure the flow rate of various clean liquids in circular pipes at room temperature (20 C). The object of flowmeter can be changed by modifying the propagation speed parameters of ultrasonic wave in the medium under test.

Key words: Ultrasound, Time Difference Method, Flowmeter, Single Chip Microcomputer

目录

摘要…………………………………………………………………………………2

Abstract……………………………………………………………………………3

第一章 绪论…………………………………………………………………………7

1.1流量计概述………………………………………………………………………7

1.2测量技术的发展历史……………………………………………………………7

1.3测量技术的发展现状……………………………………………………………8

1.4超声波液体流量计的介绍………………………………………………………9

1.4.1超声波流量计的定义……………………………………………………9

1.4.2超声波流量计的原理……………………………………………………9

1.4.3超声波流量计的特点及应用……………………………………………9

第二章 时差法超声波液体流量计的原理………………………………………12

2.1超声波的介绍…………………………………………………………………12

2.1.1超声波的物理特性……………………………………………………12

2.1.2超声波传播时的波形…………………………………………………13

2.1.3超声波的传播特性……………………………………………………13

2.2超声波的传播速度……………………………………………………………14

2.3超声波流量计的检测原理……………………………………………………15

2.4流量的计算……………………………………………………………………16

第三章 时差法超声波液体流量计设计…………………………………………17

3.1超声波换能器…………………………………………………………………17

3.1.1 超声波换能器的划分…………………………………………………17

3.1.2超声波换能器的原理与结构…………………………………………17

3.1.3超声波换能器安装方式………………………………………………19

3.2硬件系统设计…………………………………………………………………20

3.3时差法超声波液体流量计电路的设计………………………………………21

3.3.1超声波发射电路………………………………………………………21

3.3.2超声波接收电路………………………………………………………22

3.3.3按键调节电路…………………………………………………………23

3.4误差分析………………………………………………………………………23

第四章 软件设计…………………………………………………………………25

4.1系统流程设计…………………………………………………………………25

4.2程序设计………………………………………………………………………26

4.2.1主程序…………………………………………………………………26

4.2.2 按键处理程序…………………………………………………………26

4.2.3数据显示程序…………………………………………………………26

4.2.4超声波时差读取程序…………………………………………………27

4.2.5结果显示………………………………………………………………27

总结致谢……………………………………………………………………………28

参考文献……………………………………………………………………………29

附录…………………………………………………………………………………30

第一章 绪论