Design And Developing Of Ultrasonic Heat Meter

Heat Meter is used to measure and show the energy that is released or absorbed by water flow passing through the heat exchange system. It consists of three parts, flow sensors, temperature sensors and heat calculator, and is mainly applied to measure heat energy in residential units, warming buildings, district heating stations, heat exchange stations, thermal power stations and the centralized heating system. According to the "Building Energy Conservation" 9th Five-Year "Plan and the 2010 plan" ,issued by China's Ministry of Construction in 1995, household measuring and charging system of China's domestic centralized heating systems will be fully implemented in 2010. After 10-years reforming process, the reformation of towns heating system has entered the mass-production time of metering facilities and the sprint stage of its installation and debugging. However, the main body of present domestic heat meters is still mechanical-based production, which has high demands on water quality, large loss of pressure, easy abrasion of mechanical parts and other shortcomings and it doesn't meet the demands of market. Whereas, ultrasonic heat meter is a kind of high-performance heat meter, it has the advantages of high-precision, low-demand on water quality, low-loss on pressure, and high-reliability. Then, the experts and some relevant departments regard it as a new generation of heat measuring instruments that to be developed vitally.This dissertation is going to develop a kind of ultrasonic heat meter, it measures flow by time-difference ultrasonic and measures temperature through charging and discharging of a capacitor. The work principle and composition of heat meter are systematically analyzed. It also researches the water flow measurement principles of time-difference ultrasonic flow and temperature measurement principle during capacitor charge and discharge as well as their respective methods of achievement. The two key modules of flow measurement and temperature test of heat meters are reunified to the very problem of time measurement. The high-precision time measurement is gained by the help of a high-precision timing chip. This system makes fully use of the selected time-chip, which has the advantages of full-function and low power consumption. So, according to the points above, this heat meter prototype has the characteristics of high-precision, low-cost, low-power consumption and so on.The first chapter of this dissertation, based on a large number of domestic and foreign heat meter literatures, introduced research background and present situation, classification and characteristics. The composition and structure of ultrasonic heat meters, its measuring principle and the development of the status both at home and abroad are emphasized. Then, the subject of this research is illustrated.In the second chapter, ultrasonic flow detection technology was systematically analyzed. It focuses on ultrasonic flow measuring principle that adopts the time-difference method in this issue. By analyzing the factors that impact measurement accuracy, the design notices are put forward, the time measurement technology is studied, and then the design method of this system is identified.Chapter three introduced the temperature measurement principles and the heat algorithm, determined a temperature measurement program by platinum resistance sensor with assistant of charge and discharge capacitance. The mathematical model of heat energy algorithm and software achieving methods are also explained.In the forth chapter, the specific design elements of ultrasonic heat meter table was introduced. It includes the design of ultrasonic transducer, the selection of temperature sensor, the mechanical structure of pipe and install methods of sensors.The fifth chapter introduces the key technology of this issue. It includes the hardware circuit design of the second meter of ultrasonic heat meters and its related software achievement methods.In the sixth chapter, the performance of the heat meter prototype is tested through experiments. The corresponding testing experiments were done respectively to flow sensors and temperature sensors, and then the parameters of the prototype were determined.