| 摘要 |
PURPOSE:To measure the flow rate accurately at a high SN ratio, by varying an exciting current in response to a flow speed, and obtaining the speed from the variation. CONSTITUTION:An electromotive force corresponding to the flow speed of fluid is generated at detecting electrodes EDa and EDb in a pipe P and applied to an amplifier AMP1. A one polarity pressure signal e1 is compared with a reference voltage es in a comparator amplifier CA1 through a resistor R1. Based on a differential output e2, a current I is imparted to an exciting coil CL so that the differential output e2 becomes zero through a comparator amplifier CA2 and a transistor Q. AT this time, a dividing circuit DC receives a signal corresponding to the exciting current I from an inverted input terminal (-) of the comparator amplifier CA2 and outputs an output signal corresponding to the flow speed which is obtained from the inverse number of the value of the signal I. Since the SN ratio at a low flow speed becomes high, the flow rate can be measured accurately. |
