How to Generate 4mA to 20mA Analog Signal for ADC Testing Using 30V DC Power Supply

Dear Sir,
Please I need your support on how to generate an analog signal(4mA t 20mA) for testing purpose. I have an analog to digital converter board which I want to test based on the program I wrote. To do this I need an analog signal source which will be fed into the input of the ADC circuit but at the moment I have only a DC power supply(30V/3A).
I would be glad if somebody could give an idea on how to go about it. Thank you all for the usual support. Best regards.

Hi Olade,

I think your problem is quite similar to this one: 4-20 ma driver. Although your supply is 30 V, I think the idea is the same for the design. Kindly look at it.

I hope this helps,
Kevin