2 Bit Binary Encoder with Sync
This
encoder is designed to be read by three sensors and counts those encoders in a
binary pattern. Like the Quadrature Encoder this can be used to figure out if
the encoder is turning clockwise or counter-clockwise.
The sync pulses in the inner ring give you a signal to use that identifies when the best time to "sample" the encoder sensors. Thus you would put a sensor on that ring and when its output indicated "black" you then read the other two encoders to return a binary number between 0 and 2.
The image above is being shrunk by your browser to be 100 pixels across, its native resolution is 600 pixels so if you print it on a 600 DPI laser printer it will be a 1" encoder and at 300 DPI a 2" encoder.