| There are a number of flowmeters in control and measurement industry. One of these flowmeters, Electromagnetic flowmeter (EMF) , has been widely used in instrument industry because of its unique features. Conventional EMFs are powered by 220V AC, which obviously does not suit for today's instrument design trend, namely reducing energy consumption of devices. In order to satisfy this new trend for instrument industry, portable and low power consumption EMFs are implemented in this study.The battery-powered EMF differs from conventional EMF in hardware implementation as well as software design. In hardware implementation, high performance integrated circuit is used in the amplification circuit to overcome the challenge of the amplification and A/D ( analog-to-digital ) conversion of weak signals with strong disturbing signals. Double-integrating A/D conversion with high accuracy is utilized in the EMF to eliminate noise caused by sharp pulse and AC interference. The excitation mode of the EMF is chosen as triple low-frequency exciting square wave, which has excellent zero stability and anti-interference ability as well as low energy consumption. The control core of the EMF is a microcontroller unit ( MCU ) . An 8-bit microprocessor, PIC16F877 made by MICROCHIP Inc. with...
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