how to convert 24vdc to 0-20ma

hi good people, i have been asked to look at a motorized valve which is controlled by a temperture controller, the valve has a 24v to the motor all the time and the output of the temp/controller connects up to the 10v or 20ma it can do both( only one is used) so the temp controller modulates the valve? what i am after is the contoller has been changed but it is different it is a relay output how can i covert 24v to 0-10v or 0-20ma so i can use the relay controller? thanks stu

Sometimes it's possible to drive a motorized valve with pulses forward or reverse instead of using an analog signal. The controller in this case would have two pulse outputs.
Is your controller like that or is it one with only one relay output?
If it's not the former then you may have to purchase a different type.
Roy

Not going to happen with a relay output. That's probably a controller designed for electric heaters not a proportional valve. Invest in the correct controller.

Using the on/off output signal from the new controller will turn the proportional valve into an on/off (open/close) valve,
but maybe that's the whole idea?
You can use a smaller value for the bottom resistor to suit your needs: The valve will open less when controller output is on.

Give us the make and model of your valve and controller we will be able to advise you further.
Roy

hi i have found a manual on the web for the valve
http://www.york.com.pl/pdf2/HVAC_Control_Products/silowniki/obrotowe_%20do%20zaworow%20regulacyjnych%20(4_6_8_16Nm)/M9109/jezyk_angielski/PB_M9109-xGx-5_EN.pdf

and the controller is a west 6100 part number P6100-2100-02

I'm not 100% positive, but reading the manual:

http://docs-europe.electrocomponents.com/webdocs/02c0/0900766b802c0643.pdf

It appears that you should add the linear vdc/ma output module. That should give you 4-20ma control over your valve which is what it needs.