APPARATUS FOR LEVEL DETECTING USING A MULTI SENSOR FOR DIFFERENTIAL PRESSURE

摘要

A level detecting apparatus using a multi sensor for a differential pressure is provided to avoid an erroneous detection caused by a fluid flow or impurities by measuring the measurement pressure of a chemical solution in a sealed bath or tank and a variation pressure of the inside of a bath or tank in a semiconductor or LCD(liquid crystal display) production process. A first sensor(70) is connected to a solution level detecting tube on the bottom of a sealed tank(10) containing a chemical solution, detecting a pressure variation value proportional to a solution level of a small amount of nitrogen gas supplied through the tube. A second sensor(80) detects a varied pressure value of the tank by external influence. A level detecting unit(90) stores data that the chemical solution in the tank is converted by a program according to its level and compares differentially amplified data with the converted data to detect the level of the chemical solution in the tank wherein the differentially amplified data is obtained by differentially amplifying a difference between a pressure variation value proportional to the solution level detected by the first sensor and a variation pressure value of the tank varied by the external influence detected by the second sensor. A remote panel(100) displays an alarm signal when the level detection value of the chemical solution exceeds a control condition. A network computer(110) monitors the operation process of the level detecting unit.