This is a special instrument to measure and control the liquid level of melted glass in glass furnaces. It is characterized by high measurement resolution, small fluctuation of level control, simple operation, and high stability and reliability. This instrument has many functions such as digital display of relative height, LCD real-time display of level variation curve, manual/automatic switch-over, interrupted and continuous feeding output, upper/lower limit alarm indication, sound-light indication, and self-testing, etc. It is an ideal level detecting and control instrument for the glass industry.