| 摘要 |
PURPOSE:To arrange so that a stable measurement free from an error may be obtained, by transmitting a transmission frequency after changing it to a frequency of an extensive range periodically instead of making it a single frequency, and receiving the maximum value of the transmitted frequency. CONSTITUTION:A level gauge holding an ultrasonic transmitter part 1 and an ultrasonic receiver part 2 opposed to each other keeping a constant space l, is installed on a detected part for a surface measurement. Then a variety of standing waves (a), (b), (c)... are sequentially changed and transmitted at a constant period by means of a frequency modulation circuit 6. The maximum frequency is selected and detected from among received signals of these various frequencies by means of a rectification circuit 10. For this reason, even if these were a change in the frequency, a change in the receiving sensitivity does not occur through the mutual compensation of frequencies, thus obtaining a constant sensitivity on the average all the time and detecting the surface of a suspension. |
