A plastic housing protects the sensors and provides a robust connection to PC boards. The devices use an infrared LED/phototransistor pair to measure changes in the refractive index as an infrared signal passes through the tube and liquid. The sensor generates an output signal that can be read by external reference circuitry to describe multiple output states, such as: "fluid present," "no fluid present,'" or "no tube present," as well as specialized functions like bubble detection. This gives a reliable method of detecting the presence or absence of fluids in clear tubing without a break in the tubing or the need to make contact with the fluid. Operating temperature for the sensors range from 40 to 85°C.

Optek Technology, 1645 Wallace Dr., Carrollton, TX, 75006 (972) 323-2200, optekinc.com