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Thrubeams

Thrubeams, or thrubeam pairs, are photoelectric sensing devices packaged in two separate housings. One part, the light source, produces light and projects it as a narrow beam. The other half of the pair, the photodetector, is positioned some distance away facing the light source so it can sense the emitted light.

When the space between light source and photodetector is clear, the photodetector is brightly illuminated and electric current flows in the photodetector circuit. A target is detected when an opaque object blocks the beam path - the photodetector is darkened and conducts less current. An amplifying control monitors the flow of current in the photodetector circuit and turns a switch on or off when necessary. Because of this high contrast between light and dark states, a thrubeam provides highly reliable indication that a target is present.