| 摘要 |
A pulse generator (3) is controlled by a temperature sensor (5), which detects the temperature of the medium, in such a way that the output frequency (f3) of the said generator (3) exhibits the same dependence on the temperature of the medium as the square of the speed of sound in the medium. A measuring device (4) which is connected to ultrasonic converters (1; 2) and to the pulse generator (3) generates metering pulses, the frequency (f4) of which corresponds to the product of the output frequency (f3) and the difference in the transit times of the ultrasonic pulses received by the ultrasonic converters (1; 2). The output frequency (f3) is composed of a constant frequency (f1) and a variable frequency (f2) which depends on the temperature of the medium. Failure of the temperature sensor (5) does not interrupt measurement, but merely causes measurements to be somewhat less accurate. <IMAGE> |
