[Al_The_Man]

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.

[PCW_MESA]

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.

Not only wrong about quadrature but also the number of tracks, its possible to use two tracks but its
normally a bad way to do it, Normal quadrature encoders use a single track and offset detectors/ Ronchi gratings

[Al_The_Man]

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.