resistance readings

[halfintegerspin]

so i have just wound my first pickup.  when the coil was wrapped i measured 6.22k, about where i wanted it... i then 'charged' the magnets in the questionable manor suggested by stew mac: Nd-magnets... i then measured the resistance again, and noticed it went up... does this make sense?  it didnt go up much, like 0.05k, but is this normal?  i have no idea what the field strength is... if this is normal is there a way to estimate the filed strength based on the resistance hike?  sorry for the overly sciencey question... i try and avoid those...

 

[mayfly]

In theory the magnets should not change the impedance of the pickups - unless there was something that was exciting the magnetic field (like a vibrating string near by).  Then all bets are off.

The other thing it could be is measurement error.  What sort of meter is this?

 

[Patrick from Davis]

With the thin wire used in pickups you might be able to knock the reading around with a temperature change, like holding it with your hand.  I know that Germanium transistors are annoyingly sensitive to this, but I have never checked to see if this is the case with a pick up.
Patrick

 

[TroubledTreble]

Yes the coils are quite sensitive to temperature. The different reading may also be just how well of a connection the test leads are making. The difference you mentioned is nothing to be concerned with.

Congrats on winding your own! You could have just turned down a very long road that leads to the never ending quest to wind the next one even better and the search for "that" sound.  :cool01:

Magnetizing the alnico can be a little tricky. It is important to not let the neo to touch the alnico. Just stick a piece of thin cardboard between to keep them apart. It is best to fully magnetize/charge them then take some away if you want. There are several ways to do that. It is not possible to guesstimate the field strength. The field strength is measured in Gauss. Each type of magnetic material is capable of a different amount. More importantly there is a maximum amount they can hold. The only way to measure the field is to use a Gauss Meter.

Have fun!

 

[halfintegerspin]

thanks for the responses... the meter is a Protex 506... something from my lab, so i imagine it could be totally awesome, or total junk... it looks like a nice meter though. 

the temperature thing makes a good bit of sense... i was charging the alnico by placing a Nd magnet on a folded notecard and moving it along the length of the pickup... this of course would heat up the whole thing as it was in my hand...  i remeasured them today and the reading is lower that it was two days before, so yeah, this corresponds with the drop in temp where i live... good call.  :icon_thumright: