| 摘要 |
PURPOSE:To measure a flow rate stably without any variation in span by delaying a synchronizing signal corresponding to the delay of an exciting current even when the exciting current is delayed and moving the timing of its switching. CONSTITUTION:A reactangular-wave exciting signal is impressed to the input terminal (+) of a comparator 20 from an exciting signal generator 19 and a reference voltage proportional to the exciting current is impressed to the input terminal (-). Then, the comparator 20 turns on and off a switch circuit 21 to generate the exciting current corresponding to the exciting signal. A magnetic field which is proportional to the exciting current is impressed to fluid to be measured and a signal voltage is developed at the output terminal of an amplifier 14. A comparator 31, on the other hand, compares the reference voltage with the mean value of the reference voltage proportional to the exciting current as a threshold value to generate a delayed synchronizing signal. This delayed synchronizing signal is delayed corresponding to the response lag of the exciting current by the exciting signal. Then a synchronous rectifying circuit 24 rectifies the signal voltage synchronously with the delayed synchronizing signal as the reference voltage and sends an output signal. This output signal is smoothed 25 and outputted through an amplifier 26 and an output circuit 27.
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