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Should I pour a ground plane under a hall-effect switch?

Derek
Mastermind 9802 points


Hello,

   I have a wireless device that has 2x C cells beneath the board, and needs to be sensitive to a magnet above the board. Should I pour a ground plane beneath the Hall Effect sensor, or will that decrease its sensitivity?

  • 0
    TI__Mastermind 20985 points
    Is the PCB between the Hall sensor and magnet?

    Having GND planes between the magnet and sensor has a minor attenuating effect. I measured a -12% difference in the field at the sensor after passing through two 1.5oz copper planes (e.g. 5mT versus 5.6mT). So if you have the flexibility, I would avoid placing metal in between, but if PCB routing would otherwise be difficult, doing so shouldn't be a problem.
  • 0 in reply to RE
    Mastermind 9802 points
    The BCB is below the Hall sensor. The magnet is about 2mm above the hall sensor. There's no metal inbetween the sensor and the magnet.

    Will the ground pour beneath the Hall sensor help or hurt sensitivity?
  • 0 in reply to Derek
    TI__Mastermind 20985 points
    Ok I see. Pouring a copper ground plane below the surface-mount Hall sensor should make an insignificant difference, if any. Pure copper isn't a ferromagnetic material, and it shouldn't significantly affect magnetic fields. On the contrary, factors like sensor-to-sensor variation in BOP, magnet variance, and mechanical variance should be top considerations.

    Best regards,
    RE