Depends on your project parameters but I used plenty of both DC and AC current transducers from CR Magnetics. Other companies make the same or similar including inexpensive versions off the boat from China. Here is an example of a CR5220 DC Hall Effect Current Transducer - 4-20 mA DC output from CR Magnetics. Using a shunt as you pictured I have used plenty of shunt amplifiers designed specifically for use with DC and AC shunt applications. Inor signal conditioners come to mind as well as others. Sounds like all you are looking for is a signal conditioned to take a signal off a shunt (0 to 50 mV) and give you a signal you want (4 - 20 mA) which you can scale for your application. Any of these solutions off the shelf turn key will avoid problems like Dick mentions above.Basically, I am having a hard time sourcing a DC current transducer that meets the project parameters.
by Duane Benson
by Duane Benson
by Jake Hertz
by Aaron Carman