GB1329968A - Analogue-to-digital converters - Google Patents

Abstract

1329968 Analogue/digital converters SMITHS INDUSTRIES Ltd 2 Oct 1970 [2 Oct 1969] 48580/69 Heading G4H An analogue to digital converter for providing a digital representation of an input angular displacement # comprises an A.C. reference source 5, a synchronous resolver 3 for providing a signal having a magnitude dependent on #, a comparator 13 for comparing the magnitudes of the reference signal and the signal from the resolver to define an interval of time dependent on the magnitude of 0 and a counter 18 for providing a digital representation of the duration of the time interval. The resolver 3 has a rotor 2 carrying a winding 4 connected to the source 5, and a stator 8 having windings 9, 10 in which signals having amplitudes dependent on sin # and cos # are induced. One of the signals induced in the windings 9, 10 is fed via a changeover switch SW to a phase-sensitive demodulator 12 which supplies a D.C. signal to the comparator 13. The level of the D.C. signal determines the time interval during which a flip-flop 14 maintains a gate 17 open to supply the counter with clock pulses from a frequency multiplier 19. When the magnitude of # exceeds 45 degrees the counter overflows and an output to the switch SW causes it to select the cos # signal from the resolver. Outputs 21, 22 remove any ambiguity as to which quadrant # lies in. In a modification three phase stator windings of a synchro-control transmitter may be connected to a transformer.