| 摘要 |
PROBLEM TO BE SOLVED: To provide a small oxygen content meter intended to be installed in an apparatus, which improves responsiveness to gas concentration change and reduces a failure risk of a control electronic circuit.SOLUTION: An ultrasonic gas concentration meter 5 uses one ultrasonic vibrator 4 performing two operations of transmission and reception to measure a time required for an outgoing ultrasonic sound to be reflected from a reflection plate 6 provided with a certain distance, and includes an ultrasonic vibrator of 100 kHz or greater so that residual vibration of the vibrator is decreased before the time when an ultrasonic sound reflection wave arrives. The ultrasonic gas concentration meter further performs measurement by programming of a microcomputer so that reception waveform processing is not executed until residual vibration caused by ultrasonic emission stops and so that only a reflection wave is determined to measure propagation time, thus obtaining an accurate propagation time. The reception waveform is amplified 1,000 times or more with an amplifier, is all-wave rectified, and is thereafter used as a trigger signal for acquiring propagation time. Thus, an electronic circuit configuration is achieved which can perform measurement with reduced measurement error. |
