Importance

Loading Importance Indicators...

Abstract

An improved method and apparatus for measuring the length of an open pipe includes a sound transducer placed in spaced open air communication with the interior of the pipe at a selected end. A logic circuit is employed with the transducer for producing a square wave sound pulse that is directed at the pipe's selected end. An oscillator provides an ambient temperature modified count in accordance with the time required for the pulse to travel the length of the pipe and return. For compensating for error tending to be introduced because of the spacing of the impedance reflective surface at the far end of the pipe, a standoff device establishes such a distance between the transducer and the selected end of the pipe as to effect an adjustment in the duration of the oscillator count that corrects for the error. In another embodiment a microprocessor is employed with the transducer to produce two successive square wave sound pulses to effect an adjustment in the count of an oscillator clock to avoid a false reading due to the above-mentioned spacing of the reflective surface. The amplitude of the greatest peak of the first pulse is measured. The gain of an amplifier is then adjusted to make a timer stop, modified in accordance with ambient temperature, during the reception of the echo from the second pulse when 40% of the amplitude of the peak echo is obtained.

Loading the Abstract Image...

First Claim