I suspect that others are as confused about your question as I am because there's no answer after a couple days.
What do you mean by the 'range' of a PID Controller? Its input is its input (considered 0-100% by the controller), its calculated output is 0-100% unless configured to some limited output range, say, 0-75%.
Are you talking about some other 'range'?
What rating are you referring to for field equipment? Hazardous area rating? Some other rating?
If the PID output is 4-20mA then presumably the positioner or final control element input is also 4-20mA, so one uses either an I/S barrier or conduit and seal-offs for Explosion proof.
The input is usually 4-20mA or 0-100%. 0% being 4mA and 100% bringing 20mA. The controller is tuned in its Proportional band, Integralrate, and Derivative Rate. The controller will calculate the output of 4-20 mA output to the final control element of valve. The IS barrier and cable seals have nothing to do with the controller.