| 摘要 |
PURPOSE:To prevent the invasion of disturbance noise, by taking out the change in the line voltage generated when an exciting current is changed over from an exciting wire supplying a current to the exciting coil of a measuring pipe from an exciting circuit to rectify the same and driving an amplifier by the obtained DC. CONSTITUTION:The measuring pipe 11 provided to an electromagnetic flowmeter main body 10 is excited by exciting coils 12a, 12b to detect the electromotive force induced in a conductive fluid from a pair of electrodes 13a. The electromotive force is amplified by the amplifier 21 of a pre-processing part 20 and subjected to required signal processing by the operational processing part 31 of a signal converting part 30 to output the signal proportional to a flow rate. The voltage change in the line voltage generated when an exciting current is changed over is taken in a transformer 23 from exciting wires 14a, 14b, which supply a current to exciting coils 12a, 12b from an exciting circuit 32, through a condenser 22 and rectified and smoothed by a rectifying and smoothing circuit 24 to obtain DC and the amplifier 21 is driven by said DC. The pre-processing part 20 is arranged in or in the vicinity of the same housing as the electromagnetic flowmeter main body 10. By this method, the invasion of disturbance noise to a high impedance circuit is easily prevented and highly accurate measurement is performed.
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