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Ultrasonic distance meterDocument Type and Number:United States Patent 5442592 Abstract:An ultrasoni

Ultrasonicdistancemeter DocumentTypeandNumber:UnitedStatesPatent5442592 Abstract:Anultrasonicdistancemetercancelsouttheeffectsoftemperature andhumidityvariationsbyincludingameasuringunitandareferenceunit.In eachoftheunits,arepetitiveseriesofpulsesisgenerated,eachhavinga repetitionratedirectlyrelatedtotherespectivedistancebetweenan electroacoustictransmitterandanelectroacousticreceiver.Thepulsetrains areprovidedtorespectivecounters,andtheratioofthecounteroutputsis utilizedtodeterminethedistancebeingmeasured. A.BACKGROUNDOFTHEINVENTION Thisinventionrelatestoapparatusforthemeasurementofdistanceand, moreparticularly,tosuchapparatuswhichtransmitsultrasonicwaves betweentwopoints. Precisionmachinetoolsmustbecalibrated.Inthepast,thishasbeen accomplishedutilizingmechanicaldevicessuchascalipers,micrometers,and thelike.However,theuseofsuchdevicesdoesnotreadilylenditselfto automationtechniques.Itisknownthatthedistancebetweentwopointscan bedeterminedbymeasuringthepropagationtimeofawavetravelling betweenthosetwopoints.Onesuchtypeofwaveisanultrasonic,oracoustic, wave.Whenanultrasonicwavetravelsbetweentwopoints,thedistance betweenthetwopointscanbemeasuredbymultiplyingthetransittimeofthe wavebythewavevelocityinthemediumseparatingthetwopoints.Itis