All sensing and control applications use shunt-based current sensing which is prone to resistive loss, amplification noise, and high-side, low-side polarity limitations. Why can't we just use Hall-effect ICs which seem easier to use?
I haven't looked lately but for all of my career the answer to that was:
- not good at low currents
- susceptible to external magnetic interference
The one good use for those is in the feedback type of current sensors such as made by LEM, but those are very expensive.
Two major advantages of a series resistor over a Hall-Effect IC are simplicity and reliability.
Simplicity. The resistor is a very common part, readily available from a large number of suppliers at much lower cost.
Reliability. The resistor is very simple and thus a very reliable component. When it fails, the resistor will almost certainly go open circuit and disconnect the load. The HE IC will not.