It’s something [mircemk] demonstrates, with an Arduino-powered magnetic field strength meter that uses a UGN 3503U Hall effect device. The circuit is extremely simple, comprising the sensor, an ...

might be specific to the sensor too. the ones im using puts out a signal between 1 and 4 volts. the adc expects 0 to 5. so you lose some resolution. you could do away with this with a double ended ...