A MINIATURE SEPARATION SENSOR FOR WIND TUNNEL MODELS

THIS PROPOSAL DESCRIBES A NON-CONTACTING SENSOR FOR MEASURING THE DISTANCE BETWEEN ARTICLES LOCATED IN A HYPERSONIC WIND TUNNEL. THE SENSOR SIZE IS 5-INCHES LONG X 0.1-INCH DIAMETER AND ITS RESOLUTION IS 0.002 -INCH. THE BASIC PRINCIPLE USED IS PHASE SENSITIVE OPTICAL RADAR: A LASER DIODE IS MODULATED AT 1000 MHZ AND LASER RADIATION REFLECTED FROM A TARGET OBJECT IS DETECTED. THE PHASE OF THE DETECTED MODULATION IS A LINEAR FUNCTION OF THE DISTANCE BETWEEN THE SENSOR AND THE REFLECT ING TARGET-ONE CYCLE OF PHASE FOR EACH 5.9-INCHES OF SEPARATION. OPTRA HAS DEVELOPED A ROBUST TECHNIQUE (HARDWARE + FAST ALGORITHMS) FOR MAKING SUCH PHASE MEASUREMENTS WITH A RESOLUTION OF 1/3000-CYCLE, OR DISTANCE RESOLUTION OF 0.002-INCH. IT IS PROPOSED TO USE OPTICAL FIBERS TO LINK THE SENSOR PROBE TO THE DATA-PROCESSING MODULE, SO THAT THE PROBE WILL CONTAIN ONLY PASSIVE ELEMENTS AND CAN BE MADE TO WITHSTAND HIGH TEMPERATURES. THE SPECIFIED RANGE OF THE PROBE IS 0 TO 1-INCH, ALTHOUGH WE EXPECT TO BE ABLE TO ACHIEVE A WORKING RANGE OF AT LEAST 0 TO 2-INCHES. IN ADDITION TO ITS UTILITY IN WIND-TUNNEL MEASUREMENTS, OPTRA EXPECTS THAT SUCH A SENSOR WILL FIND WIDE APPLICATION AS AN INDUSTRIAL SENSOR, PARTICULARLY IN PROCESS AND MANUFACTURING CONTROL APPLICATIONS.