METHOD OF SETTING MOIRE FRINGE TRANSDUCER READING HEAD SKEW ANGLE AND INPUT STAGE AMPLIFIER GAIN AND BALANCE

摘要

1427085 Setting skew angle of moire fringe transducer photo-electrically BENDIX CORP 30 July 1973 [28 Aug 1972] 36090/73 Heading G1A A method of setting the skew angle of a moire fringe transducer reading head 10 including a grating (not shown); photo-cells 14, 16, 18, 20 each producing a cyclically varying electrical signal in response to fringe movement relative thereto; differential amplifiers 26, 28; D.C. potentiometers 30, 32 for setting the D.C. level of output signals from the amplifiers; variable resistors 34, 36 for setting the amplitude of the amplifier output signals at a predetermined value; comprises the steps of:-adjusting potentiometers 30 or 32 to obtain a zero D.C. level at test point 1 or 2; adjusting the reading head grating skew angle relative to the mesh scale grating for maximum A.C. amplitude at point 1 or 2 and to achieve one light and one dark area across the reading head grating width; adjusting potentiometers 30, 32 for zero D.C. level at points 1, 2; adjusting resistors 34, 36 for a predetermined A.C. amplitude at points 1, 2; adjusting the reading head skew angle until the A.C. signal across points 3, 4 at the outputs of square wave generators 44, 46 corresponds to that which would exist for two signals of the predetermined amplitude and being exactly in phase quadrature. Since the inputs to the square wave generators are also fed to inverting amplifiers 40, 44 there results altogether four signals of relative phase, 0 degrees, 90 degrees, 180 degrees and 270 degrees and of zero D.C. level.