Agrowtek SXL Optical Liquid Level Control KitDetect & Control Fluid Levels With These Compact, Rugged, & Economical Infrared Liquid Sensor Kits Electronic optical liquid sensors are durable, have no moving parts and are easy to maintain. SXL sensors can detect fluid levels in tanks, flow in pipes, or leaks in drip pans when liquid touches the sensor tip. Wide voltage range and high current capacity makes the SXL sensor practical for TTL logic, industrial PLC or direct relay control applications.