Encoder

Its so that you can use the phase of the signals to interpolate the position much more accuratly, as well as to use that information to tell you which direction the encoder is being turned.

The Index marker also allows you to determine the position of the encoder at start up or in absolute position with out having to turn the encoder through the zero reference etc...

John.

Dear Sir,

thank you for your kind reply, but am i thinking correct, that such kind of signals are being used as 1x, 2x, 4x, and etc....by the way i am known that the reference signal is being used for the reference mark to initiate the counting. Thank you.

Then why did you ask if you knew everything already????

Hmmmmmmm most questioners ask a question and are never seen again, this one replies that he knows it all any way!!!

Can't win.... John

You are so right!!!!!

At least its a new slant on CR4.....

If you and Andy were 1/2 as smart as you think you are, you would have noticed that your reply was NOT from the person that asked the question...

If you were only half as dumb as you really are you might have realised that all guests are effectively the same person.......

But only people with reasonable intelligence and manners get a CR4 Nom de Plume.....so that they can be identified and stand up and be counted for their opinions....

....you stand little chance on either score!

Generally speaking we mostly ignore guest opinions as simply not worth anything as there is no character backing the opinion up.

That is not the same as that we try and help guests, but once one of your sort arrives on the scene, we lose interest quickly!! The water gets too dirty....

Start taking the pills as soon as you can, it will help in the long run.....

Dear Sir,

It was not my intention to to make the water diry, i asked the question because i was confused and i was not being alleviated in my area with the answer, i was still confused that how that works....i mean 2x,4x...how is that working? that is why i have asked this question to your kind of esteemed person on CR4.

The answers have been posted as well, did you read through them all? Safety in all areas is part of the reason for the extra outputs.

I can only say that I have worked for a company that used many of these motors, the quality from some manufacturers is awful, they work fr a week and then the encoder disk is loose, it was only lightly glued in place.....finding that motor in a complicated robotic system, sounds easier than it was........later with improved firmware it got better, but not good.

I estimate that these manufacturing errors cost us about $400,000,000 over a 2 year period....our supply department would not believe us at first, it took a year for them to react and find a new supplier.....

....or the manufacturer that produced chips for us that had loose bits of silicon and metal rattling around inside the hermetically sealed chips, that depended on how the board was orientated before insertion as to how good the chip would work or not? By lying them flat on one side, we found that a sharp hit or two on the board would give us weeks of problem free usage. Lay them on the other direction and you could hardly get the unit to power up!!!! 10 boards the same type, maybe only 2 with the problem, getting tooled up at another supplier cost 8 months alone.....

Dead components are easy to locate, digital chips that "change their mind" or motors where the encoder is "mostly" in the same place - occasionally are not!!! 2 years of problems, $800,000,000 or more effective problems for us and our customers.....

1. The encoder will probably work ok with just one output, but in secure applications such as a petrol pump the second, (and third) outputs provide a functional check. With just one output, if it failed the pump would continue to deliver fuel without counting the delivery and the motorist would get free petrol!

2. The second output is also used to detect reverse rotation which could cause serious damage in some machine applications.

3. The more outputs you have the more accurate the positional output will be so your rotary encoder should be chosen with this in mind.

A is one phase, B is another in quadrature (90 deg phase shift) A- is inverted A, b- is inverted B. I is index (one pulse per rev) I- is inverted I.

You can tell direction by where in one cycle of A that B changes state or vice versa. The basic encoder resolution is increased to 4X either single phase.

Sequence for one direction is:

A = 0, B = 0; A = 1, B = 0; A = 1, B = 1; A = 0, B = 1; A = 0, B = 0; etc.

The complementary outputs (A-, B-, and Z-) are used to wire the signals in a differential fashion for increased noise immunity, as opposed to single ended.

In a differential set up the signals are compared to each other A to A-, in a single ended set up, the signals are compared to ground.

Here is a blog post on preferred wiring for rotary encoders that mentions this:

http://quantumdevices.wordpress.com/2009/02/26/preferred-wiring-methods-for-optical-encoders/

Quadrature is the counting of pulse edges as opposed to the pulses themselves. Since the A and B channels are out of phase you get a two rising and falling edges for every direct read point of resolution.

This should not be confused with interpolation where the signal read directly from the encoder disk is chopped up into a higher number of counts.

Quadrature and Interpolation are different.