How Do U Measure Uninstalled Pickup DC Resistance?

mike shaw

Member
Messages
2,213
You need a multimeter (DMM). Set the DMM to it 20k ohms setting and attach one probe to the 'hot' pickup lead and the other probe to the 'ground' lead or shield.
That's it!
 

tdarian

Platinum Supporting Member
Messages
5,037
Can the DC resistance of humbucker pickups be measured if they are installed in a guitar and soldered to the pots, etc? If so, does anyone have a resource or tutorial for doing so accurately?

I have a Fluke 87 V (that I've never used).:huh
 

Zexcoil

Vendor
Messages
5,725
It'll be a little off, but if you always do it that way and reference to the same pot values, you'll have at least a self consistent database.

I do not use installed values for my database, but I will regularly do spot checks (for instance just to make sure everything is working before I screw the pickguard back on and tighten up the strings! ARRRRRGH!!!)

Make sure all of the pots are on "10". Also, what I've done is clip off an old guitar cable, so I have an RCA plug on one end and bare wires on the other. Just plug this test cord into the guitar jack and test the DCR (or more preferably ACR and inductance!) across the exposed leads.

If you don't want to make a test cable, just plug in a normal cable and measure the DCR across the tip (hot) and the shaft (ground) or really any grounded part of the guitar.
 

Zexcoil

Vendor
Messages
5,725
...rememeber, when "installed," the VOL-pot is connected in parallel across the pickup (depending upon switch selector setting), so you're reading the two DC-resistance values in parallel.
True.

example:

250K pot
6K pickup

measured DCR (with pot) = 1/(1/6 + 1/250) = 5.86 which is about 2.5% low.
 

Clorenzo

Member
Messages
1,930
True.

example:

250K pot
6K pickup

measured DCR (with pot) = 1/(1/6 + 1/250) = 5.86 which is about 2.5% low.
And from that formula you can easily work out the actual resistance (R) given the one measured with the pot (Rm) and the pot value (P):

R = (P * Rm) / (P - Rm)
 

Rockledge

Member
Messages
5,556
Depending on where the switch is wired in the circuit, you can sometimes measure them while in the guitar by making sure the pickup you are measuring is in the "off" position at the switch.
For this to be so, the pickup has to be directly wired to the switch before anything else, you simply put the switch so that the pickup you are measuring is in the off position, then measure between the hot wire of the pickup at the switch and ground.
 




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