| 摘要 |
PURPOSE:To exactly measure the liquid quantity by ultrasonic wave in an electric hot-water heater. CONSTITUTION:An ultrasonic sensor 5 for transmitting/receiving an ultrasonic wave is provided on the covering part of a vessel 2, and the time until the transmitted ultrasonic wave is reflected by the water surface 7 and returned is counted. Accordingly, the time being proportional to the liquid quantity can be counted by the ultrasonic wave, and even if the water surface is not stable, the time counting is executed by a prescribed number of times, and its mean value is derived, therefore, the liquid quantity can be measured with high accuracy. |
