| 摘要 |
PROBLEM TO BE SOLVED: To provide an electromagnetic flow meter capable of measuring the flow rate in the forward and reverse directions by reducing the stabilizing time for the forward-reserve switching, without deteriorating the measuring accuracy of and A/D converter. SOLUTION: An electromagnetic flow meter comprises and exciting means 3 for applying an alternating magnetic fieldϕperpendicularly to a fluid flowing in a measuring pipe 1, a pair of signal detecting electrodes 2a, 2b for detecting a resulting signal electromotive force 5a, a synchronously rectifying amplifier 5 for amplifying an output 5a from the electrodes 2a, 2b synchronously with an exciting current 3a of the exciting means 3, and A/D converter 6 for converting the synchronously rectified output 5b into a digital signal 6f, and a flow calculating means 7A for obtaining the flow rate F based on the A/D converter output 6f. The flow calculating means 7A comprises a means 72 for comparing the calculated flow rate F with a flow rate threshold, and a means 73 for inverting the exciting phase of the exciting means 3 for applying the alternating magnetic fieldϕaccording to the comparison result.
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