Regarding absolute encoders

I know absolute encoders are basically sensors which can tell position. I've looked it up and they do that by using a scheme call gray code.
But what I don't understand is how and where they are hooked up. It'll be cool if someone shows a picture of a encoder "in action" (if that's physically possible)

Here is an AMCI duracoder connected to an Allen Bradley ML1500 16 digital input card. The encoder is 10 bit and uses gray code. The gray code is handled by the ML1500 which has a gray code to integer function. The card is a standard input card as it was fast enough for the application (response time = 1ms).

The is a shaft driven device that provides postion feedback for a power press.

Hey JohnW, appreciate it. But I was thinking more on how it is hooked up physically and not electrically.

This may be a language or semantics issue but physical equates to electrical.

NOTE: Depending on brand, model etc the wire color may vary, you need the manual for the specific encoder.

NOTE: Not all absolute encoders use gray code, just as many (if not more) are binary.

Take a look at this page: http://www.patchn.com/absolutencoder.html

Let me rephrase my question: Where do you physically mount an absolute encoder?

What turns the shaft? Why do I need to know the exact angle of the shaft?

Sorry I'm pretty new to this

it depends on application. you can attach encoder to just about any rotating object,
regardless how it is powered (motor, watter, wind, hand...). it can be mounted everywhere
just like incremental encoder but this is usually mechanical problem and not something we
would worry much about. absolute encoders are more expencive, units with parallel
output like yours require more wiring etc. which makes long cable runs less practical.
incremental encoders are cheaper but in most application (position measurement) they will need
homing. where homing is not practical or possible, you have to use absolute encoder.
to convert value read by encoder to meaningful engineering units you need to do scaling.
before you can do scaling, you have to convert raw value from gray to decimal binary.
scaling will have to take into account any gear ratios, number of encoder pulses per
revolution etc.

Why do I need to know the exact angle of the shaft?

Click to expand...

Let's say that the encoder is coupled to a ball screw and the ball screw has a pitch of 10 mm.

If the encoder has a resolution of 100 counts per turn, then each incremental count from the encoder is equal to 0.1 mm linear travel of the ballnut.

I did miss the point, but with this being a PLC website...

With an absolute encoder it is best to fit it to the machine so that the ratio between the machine movement that needs measuring and the encoder is 1:1, this means that on power up the encoder position reflects the actual position of the machine, otherwise there is no point in using an absolute encoder.

I generally get a mechanical engineer to fit them. I say what motion I want to measure and leave it up to them.