| Electromagnetic flow-meter, which is based on Faraday's law of electromagnetic induction, is a velocity-type flow-meter. On analyzing the development status and trend of the electromagnetic flow-meter technology at home and aboard and considering the sanitation, safety, conductance, installation and the density of the milk bought every time, a high precision measurement system is designed based on the electromagnetic flow-meter.First, research the characters of the signal which is outputted from the electromagnetic flow-meter sensor. Then design a high-powered signal-processing circuit and make use of a 16-bit analog-to-digital ship, which communicates with the ARM through SPI and improves the accuracy of the electromagnetic flow-meter. Second, design a square waveform exciting circuit with high accuracy and low power consumption, and the environment has low influence on the result of the A/D conversion. So the stability of measure system is improved. Third, adopt some anti-interference technologies, including the hardware and software aspects. For different interferences different anti-interference measures are taken action, which make the anti-interference ability, precision, stability and the measure extension of electromagnetic flow-meter improved. Fourth, analyze the characters of the signal when the air bubbles flow through the pipe or when the pipe is empty and design a method to process the signal when the air bubbles flow through the pipe and an alert circuit for detecting the empty pipe. Fifth, A 32-bit embedded chip is applied in this system. In the process of the software design, we obey the law that the software should have the characters of modularization, framework, reusability, so the software can be used recurrently. Finally, design and finish the PCB board and do experiments and analyze the results of the experiments. |
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