I need to read 3 channels of 4-20mA and output 3 channels of 4-20mA to control a process. Im looking at the NI-9203 and NI-9265. These are separate modules. Can I somehow use them together so that the Current Output Module will output a signal based on what the Current Input Module is reading. I'm new to using DAQ's so forgive my ignorance.
Yes you can do that with those modules, they are just input and output.
You will have to write a program that reads the input module and then determine the proper output. It also depends on how critical your process is to determine if you can use a CompactDAQ or CompactRIO to run your program. That also goes along with how fast the output signal responds to the input signal. So there are many more questions that will need to be answered. I would get in touch with your local NI Rep and explain specifically what you are trying to accomplish. Then get to programming!