Resistive variable output/Digital potentiometer output

Hello everybody,
I need to adapt and automate one old machine and for that case I need some kind of resistive variable output (preferable from 0 to 10kOhm). Does anybody knows is there PLC with that capabilities or some kind of convertor?

Any help would be appreciated!

Best regards,
Goran.

this should get you started

http://en.wikipedia.org/wiki/Digital_potentiometer

Please post a diagram of the circuit. Perhaps you can use the power source from the machine potentiometer to an isolated analog output card. Connect that output to where the pot variable arm would normally connect.

I know theory, but the problem is that if I do classical resistive ladder it will take at least 8DO and it is much and if change is really fast and often lifetime of digital outputs will be quite short. Also it OK when you want to change, for example, voltage output 0-10V, but from time to time I have some applications where I need to change exact resistance according to some input, so that is why I need some tested, from the shelf, solution.

http://www.sensorsportal.com/HTML/DIGEST/december_05/Potentiometer.htm

http://micronor.com/products.php?category=Products with 4-20mA Interfaces&offset=0

servo potmeter

The motorized pots are the direct answer to your question, but generally speaking, a potentiometer input is just a way of getting a variable VOLTAGE (aka potential, as in potential-meter or "poteniometer") on a circuit, and there are plenty of analog output voltage transducers out there. What I'm saying is that you might be over thinking this. For example if you must vary the resistance with a pot in a 10VDC circuit, then the circuit is really just USING the pot to change the voltage. Just change the voltage directly, foget the pot. Use a signal isolator if necessary. If it is a 120V or 240V AC circuit going through that potentiometer output, then just take whatever analog output your PLC provides and use it to feed into an SCR voltage control module, something like that. It's easier, no moving parts to wear out.