| 摘要 |
PURPOSE:To reduce the influence of power source noises even in two-frequency excitation with a large time constant by performing excitation with an exciting current which has two frequencies, i.e. a low frequency as one of the even component of a commercial frequency and a high frequency shifting slightly from an integral multiple of the commercial frequency, and detecting a generated signal voltage. CONSTITUTION:An exciting means establish a magnetic field which has 1st frequency and 2nd lower frequency. A 1st demodulating means discriminates the signal voltage generated corresponding to a flow rate by the excitation of the exciting means according to its 1st frequency and outputs the signal voltage, and a high-pass filter filters the output. A 2nd demodulating means discriminates the signal voltage according to the 2nd frequency and demodulates it, and a low-pass filter filters the output. An adding means puts the outputs of the high-pass filter and low-pass filter together by addition. Then the value of the 1st frequency is set to a frequency shifting slightly from an integral multiple of the commercial frequency and the value of the 2nd frequency is set to an even submultiple of the commercial frequency.
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