Funky capacitor readings!

[philbinator1]

Hey forum,

I just bought some small-value capacitors from Surplustronics in New Zealand, so I can finally finish my BSIAB2 i'm building...
I started the first of 3 caps i have left to add, 250 pF.  I needed to add 2 cos i only have 220 pF and a 30 pF.  anyway, I thought i'd
measure the capacitance just to be sure...and heaps of values i measured are out, even though they have the code (221 etc) on the
cap!  All the pF caps i measured are way higher than stated, the 230's measured in at about 280.

Have you guys had any issues with this before?  Could it be my DMM is funky? 

Thanks for any help.     Will see you all in 3 or four days, i'm off for a road-trip to my home town with the Mrs   

[MikeH]

Do the caps have a tolerance rating?  Ceramics can be as bad as +/- 20% (I think).  230pf + (230pf * 20%) = 276pf

Film caps should be tighter, like 5-10%.

Now you know why 2 pedals built exactly the same can sound totally different. 

[composition4]

Agreed - in addition to this, DMM based capacitance meters can be way off when measuring sub-nF values

Jonathan

[Brymus]

Yeah,be sure you zero your capacintance meter before measuring.
Also its probably better they measure higher than lower,just sort through them and use the closest matches.
They can be off a little and it shouldnt matter that much.
Bryan

[philbinator1]

Yeah,be sure you zero your capacintance meter before measuring.
Also its probably better they measure higher than lower,just sort through them and use the closest matches.
They can be off a little and it shouldnt matter that much.
Bryan

Mike - didn't know the tolerances were so big, although they all seem to be over not under.  I'l measure some more today.
I couldn't find film caps in the pF's unfortunately.
Jonathan/Bryan - I think i remember my dmm having some such button to 'reset' so i'll try that, maybe it has left-over
capacitance or something?  Anyway i'll do that.  I did wonder if it mattered if they were off, i'll try to get some closer
values with diff. cap values.  The annoying thing is, if I ever needed a cap at say, 4 pF I couldn't coz their values seem
to be 80 pF at minimum!  I'll measure more we'll see. 

Thanks guys  ^_^