| 摘要 |
PURPOSE:To make it possible to measure a short distance, by estimating the rising point of a reflected wave from the point where the reflected wave, reference voltage and auxiliary reference voltage cross. CONSTITUTION:The signal by an oscillation time setting means 2 acts on an oscillation means 1 and first and second clocking means 11, 12 to start ultrasonic oscillation and the measurement of a time. Forcible oscillation is performed for a definite time after the start of oscillation and, after masking time, main reference voltage A and auxiliary reference voltage B are generated from main and auxiliary reference voltage generating means 9, 10. An emitted ultrasonic wave impinges against an object spaced apart, for example, by 10-50cm to be reflected therefrom and a signal is generated in an ultrasonic element 4 by the action of the reflected wave. This signal is inputted to first and second comparing means 7, 8 through an ultrasonic element reflected wave receiving means 5 and a reflected wave amplifying means 6 and the reflected waves cross voltages A, B. At this time, the outputs of the means 7, 8 are reversed to stop the measurement of a time of the clocking means and the time from the point of time when the reflected waves oscillated the element 4 to the point where the reflected waves cross the voltage A, B is measured. The rising point of the reflected wave is estimated by an estimated value operation means 13 to enable the measurement of a short distance. |
