From what I have read, when placed within a magnetic field, a current will flow in both sensors.

My goal is to use this kind of sensors to guide a robot thanks to an existing automower loop wire, such as suggested in DIY Perimeter Wire Generator and Sensor.

I am thus wondering what is the difference between a Hall effect sensor and an inductive one such as the one described in the link above?

1 Answer 1


First they physically work differently. In the Hall effect sensor the electrons flowing through a plate will be deflected. Thus there will be a voltage perpendicular to the current, which can be measured. The voltage will be proportional to the magnetic field strengh. So you can sense a magnet, that is near the sensor, even if it doesn't move.

For the inductive sensor you have a guiding wire, that has an AC current flowing through it. This also means, that a magnetic field ist constantly building up and collapsing again around the wire. This change of magnetic field will induce an induction voltage in a nearby wire loop (the actual sensor). The frequency of that voltage is the same as of the guidance wire and the strength depends on the distance between the wires. So you are not measuring the magnetic field strength directly, but you measure how much it is changing (mathematically you differentiate).

Two different measurement methods which can be used to do the same thing. To guide a robot over a predefined course I would use the induction method (as long as the situation allows laying out wires), since it can be made less susceptible to noise. For that you can filter out all frequencies except of the used guiding frequency with a LC circuit. Or even better (though maybe not important) a lock-in amplifier. The hall sensor is an analog device, which can be very noisy.

  • Thus, regarding the robot guidance over a guiding wire, both sensors can do the job but measurements from the inductive one are less noisy?
    – floflo29
    Sep 24, 2019 at 7:38
  • 1
    Yes and no. I cannot say, which one is better as, as long as you are not using additional hardware. Both of them can be distorted by noise. But when you filter out all but the used induction frequency, the noise to signal ratio gets way better. For both methods you would have to test the needed current/guiding wire layout, since the magnetic field strength or it's change must be strong enough to measure it with the given sensor. I haven't build such thing myself, so I only can talk about the theory here
    – chrisl
    Sep 24, 2019 at 9:54

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