Bizarre multimeter readings

So when I first put my Angelicaster together I bought a bulk bag of potentiometers and measured every one to make sure I got the ones closest to 250K. I managed to get three that measured 250K exactly on my multimeter and I used those.

Now they've been wired up for a few months, but my new pickups are arriving today so I pulled the pickguard off and did a few tests, without removing any of the wiring... now the multimeter reads about 235K for each pot! What the heck is going on? Do potentiometers lose resistance over time? Or is my multimeter not performing consistently? Could the fact that they're now wired up to the rest of the guitar have something to do with it?

What type of multimeter are you using?

I drag out an old military TS-352/U when absolute precision is needed. Otherwise I use a cheep DVM that I picked up at Wong-Mart for ten bucks. You might check your meter's batteries an' if'n it's an analog unit, be sure to "zero" the meter before use.

Measurements should be made with the component isolated from the rest of the circuitry.

HTH

It's a digital multimeter I picked up from Home Depot last year for around 40 bucks or so. I tested the battery and the battery is good...

I wasn't measuring with the component isolated from the rest of the circuitry, though, so maybe that accounts for the difference?

Good possibility. Unsolder a coupla the leads to one pot an' re-measure. I'm bettin' you'll see the specified 250kΩ as originally installed.

Try this http://www.kinman.com/images/inside/...0measuring.pdf

HTH

+1 to Kinman's article

Trying to read the pots in circuit will definately affect the reading and result in a lower than expected value.

Okay, so I removed them from the circuit but the problem remains. They all measure about 12k less than they did the first time I measured them. I suspect the battery may be the culprit, even though my battery tester says it's fine...

Plus or minus 10 percent is no biggie with these things. For giggles, see what dc resistance you're getting from your leads by touching them together.:D

what the temperature difference from when you first measured them? it makes a difference with pickups, i'd imagine the same thing with pots. mr neel is right on, you might even expect 20% in some cases.