Hall Plate : AC input behavior?

Question

Hi All,I have a basic question regarding Hall plates for a course I am taking.  (Iunderstand the basic operation of a Hall plate using a constant DC currentsource across the current pads to sense a perpendicular magnet field).However, I have a task of investing what is the behavior of a typical Hallplate if you apply AC constant current source instead of a DC constantcurrent.Can anyone comment on the behavior of this say applying 10Hz or 100Hz?Would you just see a periodic Hall voltage in response to your MF?  Would itstill be a linear relationship?   Would the output be usable? What would bethe typical highest input frequency this device could sustain?Will the resulting magnetic flux from your alternating current inputinteract with the magnetic field you are trying to sense?Since you typically use high input currents to sense small magnetic fields,I would think that any AC current input with a large magnitude would eitherdesensitize your sensor or possibly interact with the very device your aretrying to sense?Are there any applications where you could use an AC input current source?Or is this strictly a DC current driven device?Thank you for your input.Michael.

John Popelish · Accepted Answer

The Hall effect voltage is proportional to the current through the plate, and also proportional to th perpendicular component of the field passing through the plate, so it should work fine with AC excitation. The output is one polarity when the current is one polarity, and the other polarity when the current changes direction. This should hold true till the frequency gets so high that the plate dimensions are a significant fraction of a wavelength or the applied frequency.

Not much, since the applied current creates a magnetic field that wraps around the plate, and the Hall effect is dependent on the field passing through the plate. I guess there might be some effects at the edges where the wrapping field passes through. Are you analyzing the effect, mathematically, or experimentally?

The excitation current is usually limited by the resistance of the plate and the heat that resistance produces. These limits normally keep the magnetic field from the excitation quite low.

AC excitation allows narrow band amplification and phase locked detection, which rejects lots of noise and DC drift, so it could have applications for low level sensing.

Jasen Betts · Answer

I see no reason why it wouldn't still be linear, so long as thare's no ssemiconductor junctions, or other non-linear devices involved to foul things up.

if it did not there would be no hall voltage produced.

last week someome said that low AC voltages are easier to detect than low DC voltages.

Hall Plate : AC input behavior?

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