So, is 4-20mA straight from the analog pin kosher?
Do you suppose that a digital pot might work? The only reason I'd go this way is to keep the number of power supplies to a minimum.
QuoteSo, is 4-20mA straight from the analog pin kosher?No. Even if you filter a Arduino PWM analog output you will have obtained a programmable analog output voltage, not a programmable constant current output. 4-20ma current outputs require external components.
That's a little pessimistic - given you filter the output with a smoothing capacitor you can then pass this through a resistor to turn it into a current. However you will need to know the input voltage that the controller uses for its current-sensing input - I couldn't seem to find the full specs.