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September 10, 2011


george storm

Shouldn't a coil sold for this purpose specify the alignment?

John Dunn

I agree! However, my discussion with the manufacturer was fruitless in that regard.

David Archer

Putting a coil external to the coil will not provide information about the orientation of the field internal to the coil. Any pickup on the external coil will depend on the total flux internal to the coil, which will be very insensitive to orientation. If you want to measure the orientation of the field inside the coil, you need a pickup inside the coil.

If the coils were wound in the same sense, but a different angle depending on direction, this slight effect would cancel out, and the maximum field would be along the axis. The contamination will be the equivalent of a single turn with a current equal to the current component along the longitudinal axis of the cylinder. It may be that there is not an issue, it does depend on the details of how the coil was wound.

Joe Leikhim

So, assuming the manufacturer calibrated the coils relying on the assembly's central access, their own calibration data would be skewed in the direction of under reporting the magnetic flux created by the coil. Time to select a new vendor!

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