How It Works: Light sent down into the glass rod is reflected back as long as the liquid surface level is below the glass rod. As soon as the liquid level reaches the glass rod the light is scattered away from the glass rod and the sensor detects this and gives an output. The level sensor is normally mounted on a bottle cap (GL45). It consists of a ground glass rod and electronics for detecting fluid on the rod end. The level sensor is powered by 5VDC and the output is a TTL.

When the liquid level is below the glass rod the output is high (+5 VDC), and when the liquid reaches the glass rod the output is low (0 VDC). A visual and acoustic alarm is built into the level sensor which signals light and sound through an LED and a buzzer when the liquid reaches the glass rod.