| 摘要 |
An ultrasonic Doppler flowmeter in which the transmitting and receiving transducers are located in a head that is secured to the outer surface of a pipe through which the fluid to be measured flows. The head includes a thermistor responding to the temperature of the head to temperature-compensate the flow indication of the flowmeter. The Doppler-shifted received frequency is added to the transmitted frequency and the envelope of the resulting signal detected and amplified. The Doppler signal is shaped and used to switch on a current source for a fixed time interval at a rate dependent upon the Doppler frequency. The thermistor located in the transducer head varies, in accordance with temperature, the magnitude of the switched current. The switched current is integrated and used to supply the signal to the output meter. |
