ADC OR ENCODERS?

[philipjoseph]

I need to control the position of three part in a machine (Angle, Head and Table).
Those positions need to have a small variation (less than 1/16).
Right now, that machine has a system with a motor, a shaft, a small reduction gear and a potenciometer (10k ohms) for every part ( Angle, Head and Table) and uses a lot of boards (very expensive) to control and adjust the speed of every motor according with the position.
The relation among the gears, shafts and potenciometers is arround 13 ohms by every 1/16" of movement.
I have two posibilities:
1.  I don't know if I can use the same potenciometers and read every one throught the ADC inputs.

2. Use three encoders to read the positions. If I can use the encoders,
what kind of encoders ?
What and how many PLC's?.
What configuration ?
do I need to use.

If none of those are good choose, I'm glad to recive the best one.

Thanks for all.

[support]

Potentiometer are good low cost solution if the 10-bit resolution (1000 locations) is enough for you. You can connect the potentiometer to the ADC inputs. A T100MD888 or T100MD2424 has 8 channels for you to use.

The PLC only has two encoder inputs maximum. These are quadrature type encoder. You third position still have to use a potentiometer. Encoder give accurate count to the rotations travelled, but can be quite expensive.