Level sensors (AKA level sensor switch) activate when the level of liquid or other flowing substance contained in a tank, reservoir, drum or barrel reaches a predetermined setting. There are many different types of liquid level sensors, including a float switch, ultrasonic sensor, photoelectric sensor and others. Level sensors are typically used within closed vessels and open tanks in food and chemical manufacturing, pharmaceuticals, as well as in ponds & fountains and other commercial and residential plumbing, reservoirs and sumps. Items vary by dimensions, conduit size, compatibilities, mounting style, features and other considerations.