The System Design Of Hot-film Wind Speed Transmitters

A wind speed transmitter has been designed, using the measurement theory of thermal anemometers, the least-squares fitting algorithm and a sensing and signal processing circuit, to overcome the shortage of home-made anemometers such as large in size, high power consumption, signle function and so on.The low power design methodologies are used in the system design process. Microcontroller and signal processing chips with low power consumption are selected. The static power consumption of the transmitter is 3.5mA. The modular design methodology is also used during the design. The communication with the host PC based on Zigbee is designed, and makes the transmitter have a broad market prospect in the field of wireless network.The wind transmitter designed in this thesis could synchronously measure and asynchronously display the wind velocity and temperature. There are multiple-range / units for the wind velocity and temperature during the measurement, and the output mode could be 0 ~ 10V standard voltage output mode or 4 ~ 20mA current output mode. The measurement data could be uploaded to the host PC through the communication interface. NEC uPD78F0513A MCU is the kernel processor. Sensor probe module, ranges/units set module, the external EEPROM memory module, LCD display module, 4-20mA V/I conversion module and 0-10V voltage converter module is responsible for wind speed / temperature data acquisition and signal adjustment, range / unit setting, calibration data storage, measurement data processing, display, and transmission, respectively.The design has been introduced in detail in the thesis. The domestic and international research of anemometers is overviewed in Chapter I. The development trend of wind speed measurement system has been analysed. And design requirements and main contents of the research are also described in this chapter. The thermal anemometer measurement principle and basic measuring circuits are elaborated in Chapter II. Then the system hardware circuits are given in Chapter III, and the software system is described in Chapter IV. The system calibration method is introduced in Chapter V, and the performance of the system is given in Chapter VI. At last, the conclusion of the paper and a prospect about the improvement and perfection of the instrument is given in Chapter VII.