| 摘要 |
PURPOSE:To obtain an ultrasonic type flowmeter which makes stable measurement possible in spite of abnormality in long-time detection by resetting a voltage holding means holding the voltage conversion signal from a transmitter-receiver by an abnormality signal at every constant time. CONSTITUTION:The voltage-converted DELTAT/V conversion signal 13 from the transmitter-receiver of an ultrasonic flowmeter is integrated by an operational amplifier 15 at the time constant determined by a resistance R1 and a capacitor 16 via an electronic switch 14, is applied with the bias of a reference electric power source 17, and is inputted to a voltage control oscillator (VCO)8 controlling the generation timing of the transmission pulses of an ultrasonic wave transmission circuit. When inputted with a reception abnormality signal 19, the switch 14 goes off, and causes the value of an integrating circuit to be held. An electronic switch 22 connected in parallel with the capacitor 16 is turned on by the output of a counter circuit 20 counting pulse signal inputs 21 by the signal 19. If the flowmeter is constituted in this way, the integrating circuit is reset by the output of every constant period of the circuit 20, granting that abnormality signals are inputted for a long period of time and therefore the drift of the integrating circuit is corrected. |
