A new double frequency exciting mode for the electromagnetic flowmeter

A new double frequency and rectangular waveform exciting mode is proposed, as to overcome the disadvantage of the current mode. The designed waveform is made up of two kinds of frequencies, the high frequency of 75Hz and the low frequency of 6.25Hz. The high frequency is used to reduce the interference from flow noise. The low frequency is introduced to keep the stabilization of zero. The design is established by using the FPGA and DDS technology. A 10-bit D/A converter and WCS circuit are adopted to change the voltage signal from FPGA for a current one. The design consists of a power amplification circuit as well, which has a function of magnifying the output current and boosting the ability of load. The characteristics of the new exciting mode are analyzed in details, and the design of the hardware and software is introduces. The experimental result indicates that once the new exciting mode is established, the error of differential inference and orthogonal inference can be reduced greatly. Besides, the measurement accuracy is improved at the same time.