Hall Sensor

Current sensing is easy to underestimate. An ADC reads voltage, not current. To measure current, the system must first convert current into something measurable.

The first model is: current must be transformed into voltage, magnetic field, or induced current before electronics can measure it.

Shunt resistor: current -> voltage drop
Hall sensor: current -> magnetic field -> Hall voltage
Current transformer: AC current -> magnetic flux -> induced current

These are not three interchangeable implementations of the same idea. They have different physics and tradeoffs.

Hall sensors appear in door contacts, limit switches, speed sensing, brushless motor commutation, magnetic encoders, and current sensors.

They are often thought of as “small switches that trigger when a magnet gets close”. That is usable, but incomplete.

The first model is: a Hall sensor detects magnetic field, not the object itself. Position, rotation, or current can be detected only if they reliably change the magnetic field at the sensor.