how to achieve a 4-20mA input from a 24Vdc supply

Hi there,
I am a student who is busy with a wireless device which as an analog input. How do I achieve a 4-20mA input to apply it to the device's analog terminal. A diagram would really help.

Thanks

hi,
Do you mean you want to generate a 4mA to 20mA current source, or convert 4-20mA to a voltage.?

hi thanks for the reply. I actually want to generate a 4-20mA current source from a potentiometer if possible. I have two wireless devices, the one device is the main with inputs and the other device is the receiver where a Variable speed drive to connected to it. I want to connect a 4-20mA input to the main device and will in-turn vary the speed of the motor remotely via a pot. I do I achieve this?

hi,
This is a simple 4mA to 20mA current source.

Whats the input impedance of the load resistor the current is flowing thru.?

E.