| 摘要 |
PURPOSE:To simplify circuit constitution and to miniaturize an apparatus, by detecting a signal having frequency equal to frequency deviation generated in a reflected wave to form the same into a pulse and measuring the speed of a ball on the basis of pulses passing through a gate means for a definite period. CONSTITUTION:The apparatus is constituted of a transmitting means A for sending out an ultrasonic wave with predetermined frequency, a receiving means B for receiving the reflected wave from a ball, a frequency deviation detection means C for detecting a signal having frequency equal to the frequency generated in the reflected wave, a wave form shaping means D forming the output of said means C into a pulse, a gate means E, a count means F for counting the pulse and a display means G and the period for opening the gate means E is set to a predetermined value so as to make the displayed value almost equal to the value showing the speed of the ball. By this method, an operation circuit for calculating the speed of the ball becomes unnecessary and, because circuit constitution becomes simple, a small-sized light and inexpensive apparatus is obtained.
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