Single coils : Changing DCR ...

[Strat76]

Hi Everybody,
I found that the DCR of the pup changes one hour or two after it has been wound.
For example, I take the DCR of the coil just after the winding (around 5.68K) and one hour after the DCR drops to 5.5K.
Is there any explanation ?
Does anybody find that as well ?

Thanks
Fabrice
ps : I hope you understand ;-) My English is not very good.

[copperheadroads]

If you are soldering the leads then measuring the DCR its because the soldering heats the wire & increases the dcr

[big_teee]

Also let it set an hour at room temp, check it.
That is the temp I judge them by, 70-75f.
Now put it in the refrigerator for an Hour and take it out and check it.
Your 5.8k may read 5k.
Now heat it in the sun for a while.
It may read 6.5-7k.
It's that way when you take a pickup out of the wax pot.
It will read way high until it cools.
Good Luck,
Terry

[Strat76]

Thanks for your quick answer.

No I didn't solder the leads. It is just after the winding. I measure the DCR just after the winding. After I had several pups wound, (it takes one hours or two) I measure the DCR again. Right after, I solder the leads and wax them.
So the pups are exactly the same. Nothing changed between the two measurements. Just a pause of one hour.

Yes I know that the temperature affects the DCR. Of course.
But I wondered if anybody noticed the same thing.

The only explanation I have is, as I guide the winding by hand, the friction can increase lightly the temperature of the coil.
And by consequence, increase the DCR after the winding.

[pdf64]

The change you've got is ~3.3%.
I think copper temperature coefficient is ~0.4% per degree C.
So a change of <10 C would do it, and that could happen via heater from the winder, friction, heat from hands as being handled to take off the winder.

[Strat76]

Yes it seems very plausible.

But once gain, I am sure that I am not the only one who found that ... It's very strange because I had never heard or read something about that.

Maybe others pickup makers don't measure the DCR of the pickup after the winding. Don't know ...

;-) anyway thanks for your answer.

[David Schwab]

It happens to every one of us. They read higher right after they are wound because they are warmer.

To test this out, take a pickup and read the resistance, and then stick it in the freezer for a few minutes, take it out and read it again.

This is why most winders wind by the number of turns, and not the DC resistance. I make note of about what each one of my coils should read on the meter so after they are wound I can tell if there's a problem, but I wind by turn count and not resistance.

[Strat76]

It happens to every one of us. They read higher right after they are wound because they are warmer.

To test this out, take a pickup and read the resistance, and then stick it in the freezer for a few minutes, take it out and read it again.

This is why most winders wind by the number of turns, and not the DC resistance. I make note of about what each one of my coils should read on the meter so after they are wound I can tell if there's a problem, but I wind by turn count and not resistance.

Nice, It's becoming clear for me

Thanks

[jason lollar]

we did a blog article on this
Lollar Pickups Blog » Blog Archive » Temperature and Guitar Pickup DC Resistance
I never take any resistance readings I am going to document untill they sit overnight after winding. The friction from tensioning the coil changes the resistance too much- even a couple degrees difference in air temp is measurable.
When someone asks me to make them a pickup with .2K difference in DCR i tell them to blow on the pickup for 30 seconds to a minute and they will have it- or stick it in thier pocket for a couple minutes or just hold it in your hand for a short period of time.

[Strat76]

Thanks a lot for these answers ... Now, I know that I have to take the DCR the day after ..