| 摘要 |
PROBLEM TO BE SOLVED: To inexpensively and reliably measure the speed of fluid by applying two or more ultrasonic frequencies into the fluid containing a scattering body through a pipe wall. SOLUTION: In a microprocessor 17, a high-frequency signal is generated by a high-frequency generator 108 for sending to a two-band bandpass filter 11. In this case, a high-frequency TxHi converter 101 converts the electric energy of a filtered signal into ultrasonic energy, and an ultrasonic beam passes through a pipe wall 105 and is reflected in all directions by a scattering body 106 is fluid 107. The reflection ultrasonic energy is converted into an electric signal by a high-frequency signal reception converter 103 and is inputted by an FM mixer 14, a Doppler fluctuation frequency is subtracted from an incidence frequency for obtaining a Doppler vibration frequency, and measurement is made by an A/D converter 16. Then, the processor 17 is changed to a low-frequency generator 19, a generated low-frequency signal passes through a passage at the low-frequency side of the pipe wall 105 and is measured by the A/D converter 16 as well as a high frequency. The speed of a fluid is measured according to the differential Doppler vibration frequency of the two. |
