conversion

Problem I need 4ma going to a temp controller for a remote setpoint, and I do not have an analog output card. All that I have are 24vdc discrete outputs. This is a control logix setup. I am not wanting to spend the money for an analog card and I was wondering if you can convert a 24vdc discreet output to 4ma. I do not need a range of 4-20ma just 4ma
thanks
the newbie

If the 24VDC is well regulated, e.g minimal/ acceptable drift, just apply Ohm's Law and select the appropriate resistor. V= IR, R= V/I =24/ 0.004 = 6000 Ohms. Just wire this in series with the output and you should be set.

Not knowing any other particulars of this application, you may want to get a good resistor (0.1% tolerance and a low temperature coefficient) so resistance drift is not a problem.

What is the 4mA for?

You need to consider any other devices in the loop. The 6000 ohm resistor will drop the entire 24V across it, leaving nothing to drive what ever the 4mA is for.

Most likely you driving a 250 or 500 ohm load. So subtract that from the 6000.

hello world, I'm not sure what you are trying to accomplish but I doubt very much it will work. I can't imagine why you would want a constant zero setpoint on a controller (tht's what you indicate the 4 mA is doing.) Even if you really want that, I can't figure out why you would need a PLC to control it!

If you provide some application details and even specific component models some of the guys here may save you from a long trip down an dead end road.