| 摘要 |
PURPOSE:To remove the effect of the dielectric constant or conductivity of a fluid to be measured by a simple circuit, by using the control voltage of a voltage applying circuit, when the voltage at the input terminal of a voltage detection circuit is controlled to become zero, as a flow amount signal. CONSTITUTION:An exciting power source 20 allows a current If to flow to coils 18, 19 on the basis of the St from a timing circuit 21 to apply a magnetic field to a measuring pipe 10 while control voltage VC is applied to a semiconductive plate 13 to allow charge to move to the pipe axis direction of the pipe 10 at a moving speed Ve. Therefore, the electromotive force (e) corresponding to the difference between the relative flow speed (v) of the fluid to be measured in the pipe 10 and the moving speed Ve of the charge is generated at the input terminal of a voltage detection circuit 22. By this mechanism, the speed Ve is controlled by the voltage VC from a voltage applying circuit 25. The output of the circuit 22 is set to voltage VS by the switch 23 controlled by a sampling signal Sm and rectified synchronously by a rectifier circuit 24 and the rectified voltage VR is applied to the circuit 25 and voltage VC is controlled so as to set the electromotive force (e) to zero and converted to a flow amount signal Sq in proportion to the relative flow speed (v) through a voltage measuring circuit 26 and an output circuit 27.
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