Kollmorgen Corporation

Eric D Park

Talmage Mathis

Erann Gat

An optical fluid sensing apparatus comprising a sensing tip having a conical configuration with a coating, such as a thin layer of polytetrafluoroethylene (PTFE), on the outer surface of the tip element itself. At the sensing tip, emitted light is either refracted back into a detector fiber optic cable or is lost, depending upon the relationship between the indices of refraction of the sensing tip and coating to the substance surrounding the sensing tip, i.e. the fluid or air being sensed. In order to obtain the proper relationship between the sensing tip and the fluid, the index of refraction and the bevel angle of the tip element are carefully selected in relation to the indices of refraction of the coating and the fluid to be sensed. As a result, when fluid surrounds the tip light is dispersed into the fluid and lost. When no fluid is present, however, the coating sheds any remaining fluidand the light is internally reflected and refracted back into the detector fiber optic cable. Light reflected and refracted back into the detector fiber optic cable is carried by a return fiber cable to a photodetector for sensing and signal processing.

Fiber optic fluid sensor using coated sensor tip

An error detection system is provided for a two-state fiber optic sensor. An amplified photodetector signal is sampled by each of an ON-OFF threshold detector, a disconnect threshold detector and a slope detector. The ON-OFF threshold detector monitors whether the detector signal is above or below an ON-OFF threshold value corresponding to the parameter being sensed and activates an appropriate sensor output. The disconnect threshold detector monitors the constant low level detector signal corresponding to low level light received by the detector even when the thresold detector is in the OFF state, and triggers an error signal should the detector signal fall below a disconnect threshold value. The slope detector monitors the rate of change of the detector signal. Where the detector signal changes rapidly, such as during normal sensor switching, the slope detector permits the detector signal to pass to a latch, which retains in memory the last detector signal which changed rapidly enough to trigger the slope detector and produces an output corresponding to the ON-OFF status of the last detector signal in memory. A slowly changing detector will not trigger the slope detector. Where the outputs of the ON-OFF threshold detector and the latch differ, a comparator triggers an error signal.

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Blacksburg, VA, United States of America

Eric D Park