| 摘要 |
PURPOSE:To reduce the temperature errors in the titled device, by controlling the set value of a counter to a specified value with respect to the frequency of a fixed oscillator in a forward mode, controlling the frequency of a variable oscillator to a specified value, and measuring the flow rate from both frequencies. CONSTITUTION:An oscillator 131 generates a constant frequency and an oscillator 15 generates a variable frequency. The frequencies are supplied to a pulse generator 27. A transmitter 35 drives transducers 41 and 43 through a switch 45. The received wave is given to a variable time difference frequency detecting circuit 591 through a receiver 55. The output of the crucuit 591 is fed back to a control circuit 311 and an oscillator 15. In the forward mode, the control device 311 controls an N setting device 313 and controls the set value of a counter 61 to a specified value. Then the frequency of the oscillator 15 is controlled so that a specified relationship is obtained with respect to the set value of the counter 61 which is set in the reverse direction mode. A CPU315 measures the frequencies of the oscillators 131 and 15, computes the flow speed of the medium to be measured, can obtain the flow rate, and can compensate the errors due to temperature change. |
