| 摘要 |
PURPOSE:To determine an AC frequency for measurement automatically by detecting the quantity of variation with a measurement signal of every frequency and obtaining the frequency corresponding to the least quantity of variation automatically. CONSTITUTION:Electromotive force is generated in fluid L which flows in a measurement pipe MP with an alternating magnetic field generated by the excitation of exciting winding EC and detected by electrodes P1 and P2 to generate detection signals corresponding to the flow velocity. The signals are amplified by amplifiers A1 and A2 and sampled individually through serial resistors R1 and R2 and switches S3 and S4 controlled by a control circuit CF and respective instantaneous values are held in capacitors C1 and C2 and supplied to a differential amplifier DA through buffer amplifiers B1 and B2. The difference between both signals is calculated to obtain a measurement signal indicating the flow velocity, and the signal is converted by an A/D converter (ADC) into a digital signal, which is supplied to the control part CF. Then, the control part CF corrects and multiplies the output of the ADC by the sectional area of the measurement pipe MP to calculate the flow rate of the fluid L. |
