what are normal gauss readings

[RedHouse]

The only real benefit of measuring poles when a pickup is installed is when you're trying to profile another pickup w/o removing it from it's host instument, but then, that's not developing your pickup.

Simply placing the sensor under the string will measure poles on a strung guitar, if you're not able to remove the pickup it's the next best thing (hardly optimum) but even under those circumstances I loosen the strings in order to pull them away from the sensor when making my reading.

Nobody (instrument owners) minds if one turns a tuning key to slack-off a string during measurement, but back to the development notion, I don't know who does their tone development after the pickup is made, measuring the gauss at string height after you make your pickup seems backasswards.
(2 me)

[David Schwab]

Pushing the string aside is not difficult to get rid of the string effect. With small neos on top of high permeability ferrite, the difference can be 45% (using a .046). It is not clear to me how much the field is actually increased, or if the accuracy of the sensor might be affected by the magnetic material against its backside.

Mike, aren't those ferrite rods only permeable at very high frequencies?

[Mike Sulzer]

Mike, aren't those ferrite rods only permeable at very high frequencies?

It is kind of the reverse. The high permeability of this material is useful only at low frequencies (audio and somewhat above) because the losses in the material will become important at higher frequencies.

In general, materials do not lose permeability at low frequencies. Low frequencies require higher permeability material because induction is an increasing function of frequency. Go to a high enough frequency and empty space is adequate.

Power transformers (60 Hz) use lots of iron. UHF does not.

[David Schwab]

It is kind of the reverse. The high permeability of this material is useful only at low frequencies (audio and somewhat above) because the losses in the material will become important at higher frequencies.

But they use them as RF chokes and ferrite rod antennas.

[Mike Sulzer]

But they use them as RF chokes and ferrite rod antennas.

Ferrites are used at lower rf frequencies (AM band, etc.), and those ferrites have lower permeability than the one I am using for pickups.