I was perusing a few sites today and was surprised that so many offer the wrong source of the definition for a Quadrature Encoder.
The offenders all gave a variation of below. Many that should know better.!!
e,g:
"The name quadrature comes from the. four possible output states of the encoder sensor
Rather than just a single pulse indicating a slotted or striped track in a codewheel, quad encoders use a pair of tracks to go through four distinct phases. . .quad means four."
Simply not true.
The original meaning of the term Quadrature in this context meant that the two waveform's are displaced by 90°.
In fact the early Quadrature encoder simply used the two A & B signals and did not use the x4 method.
Another example of wrong dissemination of information/terminology.
Al.
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CNC, Mechatronics Integration and Custom Machine Design
“Logic will get you from A to B. Imagination will take you everywhere.”
Albert E.
The first quadrature scales I was involved in used a incandescent lamp for the reading head, they use just the two A/B pulses, one for resolution, the other for direction.
The reading of high resolution gratings is still done by the using the Moiré effect, effectively enlarging the grating resolution many times.
Al.
CNC, Mechatronics Integration and Custom Machine Design
“Logic will get you from A to B. Imagination will take you everywhere.”
Albert E.