Polydecade decimal to digital encoder

Claim 1

A converter for encoding the decimal digits represented by the successive stages of a multi-stage meter into binary coded form, each stage of said meter including a rotatable shaft which is angularly displaceable on a 10:1 ratio with respect to the higher adjacent shaft to record decimal readings of measurements effected by said meter, said converter comprising: means establishing a plurality of point light sources; a plurality of point light sensors in one-to-one optical path registration with said point light sources; a plurality of encoding wheels, one each of said wheels being mounted for rotation upon each of the said shafts of stages of said meter said shafts being intergeared in a 10:1 ratio, the plane of said wheels intercepting the light path between said sources and sensors in registration therewith, and said wheels being provided with slots extending along circular tracks on said wheels, whereby groups of said sensors are illuminated in accordance with the angular position of said wheels to provide signal outputs from said illuminated sensors; at least four said light sensors being associated with each of said encoding Wheels, said sensors being spatially distributed with respect to said slots such that a distinctive four-bit digitally encoded output may be provided for each of the ten angular positions about said wheel corresponding to decimal readings from 1 to 10, the group of said sensors associated with each of said wheels numerically exceeding the number necessary to provide said four-bit output defining said angular positions and including paired sensors in lead-lad arrangement; ane decoder logic means connected to receive the outputs from two groups of sensors and provide said four-bit digital output signals each group in binary excess three code representative of the said angular positions of said wheels in accordance with the said enabled outputs from said sensors, said decoder logic including means to generate an ADVANCE/RETARD command signal in accordance with the sensor output readings derived from the said wheel associated with the least significant digit (LSD) of said meter, and said apparatus including means for selecting one or the other of said two groups of four bit signals the outputs from four among each said group of sensors, minimizing the possibility of ambiguous readings at said higher decade.