FP-AO-210 to replace analog potentiometer?

Question

I have an old machine with 0-5V knob-style potentiometers for heat control. I wish to parallel into the potentiometer with Fieldpoint modules. Can I do this with a FP-AO-210 (0-10V output)? Of course I would only utilize 0-5V. I would use the 1601 Network interface, and power the NI system with the same power off the machine as to have the same ground. The machine has 24VDC. I need the signal isolated from the voltage output of the FP-AO-210.
I would then turn the potentiometer to zero position, and let the Fieldpoint system (in conjunction with my computer) controll the machine.
Any thoughts or suggestions with my application? Thank you in advance for your time.

Answer 1

If your existing control is truly configured as potentiometer, i.e. one end is 0V, one end is 5V and the 'load' on the wiper is not significant relative to the output impedance of the FP-AO then what you have suggested _might_ work. You won't, however, have isolation between the FP-AO and the machine it is controlling. Depending on your isolation requirements a better approach might be to use some digital outputs from an FP-DO to drive some opto-isolators and then a digital potentiometer. As an example, Dallas Semi has some stuff like: http://www.maxim-ic.com/quick_view2.cfm/qv_pk/2780
This has the advantage that you can get good isolation and the controlled machine can function at the previous setting without the FP controller being active. Lots more details will be required before you can engineer a solid solution, however, and the detail may make all of the above irrelevant. Hope this helps.
Matt