Sites that mislead.

Thread Starter

MaxHeadRoom

Joined Jul 18, 2013
20,649
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 term Quadrature in this context originally 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.
Max.
 

Reloadron

Joined Jan 15, 2015
5,424
The term Quadrature in this context originally 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.
That's how I have always interpreted it and how I learned it. That interpretation got me through about 40 years so that's my story and I'm sticking to it. :)

Ron
 

Thread Starter

MaxHeadRoom

Joined Jul 18, 2013
20,649
I was first introduced to them via Ferranti-Packard linear scales that had a incandescent lamp for emitter, every time you replaced a lamp, the quadrature signal had to be realigned using Lissajous figure on a D.B. 'scope.
I got my hands on an a course manual for them that explained in detail the necessary use of the Moiré effect in order to read a 5μm scale resolution.
Never forgot it.
Max.
 

MisterBill2

Joined Jan 23, 2018
6,008
I was first introduced to them via Ferranti-Packard linear scales that had a incandescent lamp for emitter, every time you replaced a lamp, the quadrature signal had to be realigned using Lissajous figure on a D.B. 'scope.
I got my hands on an a course manual for them that explained in detail the necessary use of the Moiré effect in order to read a 5μm scale resolution.
Never forgot it.
Max.
I have noticed that not all of the information presented on the internet is always correct. Perhaps others have noticed that as well. This seems to be such a case, or perhaps the words used have different meanings to different folks..
 
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MisterBill2

Joined Jan 23, 2018
6,008
That may be so, the thing I object to is when the (Re)definition is stated as the new truth in a technical web site, not just as a post in a forum.
Max.
That happens very frequently on the internet, even more than a month ago. Not everything posted is correct.. Yes, I am repeating myself, I do that sometimes.
 

be80be

Joined Jul 5, 2008
2,041
The problem is Quadrant doesn't mean mean 4 nor dos quad mean 4
But anything quad has has to be 4 cause most phones these days are quad core lol.

So in short people today cant see Quadrature Encoder meaning spots on a wheel read by just 2 points to see which quadrant
your going to the next one, or the one before the one your in

Maybe I should add to this quad means more then one but today it means 4 to most.
So anything starting with quad has to be 4.
Wrong a Quadrature Encoder has just a A and B
 
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BR-549

Joined Sep 22, 2013
4,938
Well, to any normal person, the word/term "quad" means 4. That's means most would think quadrature, would mean 4. Geeks and engineers are not normal people, quit fooling yourselves.

Specifically, quad means 1 of 4. And in angular notion, 1 of 4 also. Which is described as 90 degrees. It means the area of 1/4 square or 1/4 round.

In some functions, a "quad" can measure and/or control the whole system.
 

MisterBill2

Joined Jan 23, 2018
6,008
In referencing signals, for those who are engineers, "quadrature always means a 90 degree phase difference. That is entirely different from "quad", meaning 4.
And if you think THAT is confusing, just look at the nomanclature rules of organic chemistry for things that change meaning depending on which is more common. (chlorate, chlorite, chloride, chlorous, for example.)
The problem comes from folks who have no clue about things not letting total ignorance slow them down at all. Then the engineers get called in to fix things.
 

Thread Starter

MaxHeadRoom

Joined Jul 18, 2013
20,649
Well, to any normal person, the word/term "quad" means 4.
Where I have come across the confusion by some on more than just a few occasions is where they have obviously gained the definition of the term from these 'Misleading' sites as in post#1,.
When reading a component specification list for example, and come across a requirement for a 1k/rev Quadrature encoder.

For those that are aware of the true definition they know that the encoder manufacturers specification for a 1k/rev quadrature encoder is that it has two pulses 90deg apart and if needed can multiply these basic Quadrature pulses by X1, X2, or X4 .
Where those that have the wrong concept of the definition is that they will often assume the term 'Quadrature' in the spec, refers to the basic pulses x4 and will order a 255 pulse/rev encoder where they wrongly assume that the "quadrature" refers to the x4 feature.
This often occurs on sites such as CNC DIY forums etc.
All down to the 'Alternative Facts' sites!:confused:
Max.
 

cmartinez

Joined Jan 17, 2007
6,936
Quadrature simply comes from the fact that the wave forms are 90° (a Quadrant) apart.
Max.
There was a time in which I thought that the word quadrature was derived from the word square. And that that in turn was referring to the type of wave output by those devices. Other position tracking devices, such as resolvers, have sine wave outputs instead, and the word quadrature is not normally used on them, even though they too have two signal outputs with a 90° phase displacement. Also, there are three-channel quadrature encoders out there, (with one channel having a single pulse in its entire rotation, defining the 0° position of the encoder), so that proves the four-state definition wrong.
 

Thread Starter

MaxHeadRoom

Joined Jul 18, 2013
20,649
Other position tracking devices, such as resolvers, have sine wave outputs instead, and the word quadrature is not normally used on them, even though they too have two signal outputs with a 90° phase displacement. Also, there are three-channel quadrature encoders out there, (with one channel having a single pulse in its entire rotation, defining the 0° position of the encoder), so that proves the four-state definition wrong.
Actually the typical quadrature encoder starts out as two optically detected sine waves and are squared up after detection before outputing, in some cases, such as those made by Heidenhain do not square the pulses up and will use the two signals in a arctangent manner for absolute measurement.
This is also how a resolver is often used to obtain high resolution from a low resolution device.
Max.
 
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MisterBill2

Joined Jan 23, 2018
6,008
In addition to"squaring up the sine wave pulses from the sine waves, a company named "Hartridge" has an arrangement to get many additional steps per single sine wave, on their encoders. Very expensive but at the time a breakthrough. I had the misfortune to work on some of those systems. A ROYAL PAIN indeed.
 

BobaMosfet

Joined Jul 1, 2009
1,108
The root of 'quad' is 'qua', which is latin from the 1600's. Quad was first used in the 1800's. 'qua' translates as 'which way' one could argue that could be a colloquial original use for an intersection of streets, in which the most common was 4... so I think no matter how you slice and dice it, quadrature refers to something broken into parts. With the advent of 'quad' in the 1800's, it was solidified to a meaning of 4 parts. So 360/4 = 90, etc.

Thanks Max... this was fascinating. I never thought about the origin of quadrature before, it just made sense it referred to 90-deg. phase shift.
 

Berzerker

Joined Jul 29, 2018
615
Fake internet, Fake news
You mean I can't always trust what's posted on the internet,,,,Surprise, Surprise
I'm with djs ! My heart is broken, my life is shattered! Now what will I do, where will I go to get the answers I so desperately Need and must have!
Oh yea there's always books/colleges. just look at our youth today they're turning out just great.....safe spaces, animal petting therapy, free speech as long as you agree and say exactly what they tell you say and agree with and say.
I've never trusted what I read on the internet!
 
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MisterBill2

Joined Jan 23, 2018
6,008
THAT "quad" meant a 4-barrel carburetor. "409" was the displacement of the engine. Of course I realize that this had been an attempt at humor.
 
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