> When I mentioned low mass, I was referring strictly to a compass like
> device, that would indicate a slightly different direction as the
> large steel vehicle interacted with the Earth's magnetic field.

Consider "reluctor" as per electrons motorcycle ignition.

U laminations with coil and magnet in series. U facing towards
vehicle. As V passes magnetic fieldi s somewhat closed. How well and
how close needed  TBD.


        R
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