| 摘要 |
PURPOSE:To obtain a level detector which can detect the height of a liquid level of a chemicals bath 1 continuously with high reliability. CONSTITUTION:A frequency-variable oscillator 24 is provided and a speaker 19 for oscillating a sound wave and a microphone 21 for receiving a sound are fitted to the upper end of a tube 18 for detecting a liquid level. An oscillation frequency and a peak frequency of the intensity of a received sound wave are detected and the height of the liquid level is known by using the resonance of an air column of a so-called one-ended tube. Only by using one tube 18 for detecting the liquid level, the height of the liquid level can be known continuously and, besides, a detector of long lifetime and high reliability can be obtained. |
