I hate capacitor markings

[snowmix]

So I put together a breadboard arduino and it wouldn't work. I tried to use two of these capacitors I found at a yard sale marked 220 for the crystal.i

When i tested the capacitors the read .202nf and I the a 22pf should read .022nf. Are these just miss marked or something.

[T3sl4co1l]

Usually 220pF should be marked "221" and 22 as "220", but they often leave off the multiplier if it's two digits or less.  Which makes "220" versus "221" ambiguous.

Unless you specifically purchased the part from a known good supplier, and have the envelope or baggie with the exact manufacturer's part number on there, and have looked up that number to verify the value... yeah, you're pretty much better off measuring it.

So your measurement is correct, 220pF it is.

Tim

[snowmix]

I have some 10pf caps can I use two of them to get to 20pf?

[retrolefty]

I have some 10pf caps can I use two of them to get to 20pf?

 Yes if wired in parallel. However I would just try using two 10pf caps for the crystal padding. It's only likely to change the crystals frequency by a few 100 Hz, not enough to effect anything. Note the the current Arduino Uno uses a ceramic resonator rather then a crystal, so high frequency accuracy isn't an arduino thing. 

[snowmix]

Thank you guys I got it working.

Sent from my Studio Mini LTE using Tapatalk

[flynwill]

Now I know I'm getting old. When I looked at your picture I immediately though "220 pF".  Back in the day that it the way these disks were always marked.  22 pf would be marked "22".
 

[TheElectricChicken]

Thank goodness for multimeters as you get older and can't see so well. Resistor codes used to be easy to read, now the colours look all the same. I think you won't come across so many caps poorly marked as resistors hard to read. But at least we can outsmart them with meters. 3 cheers for the multimeter ! 8-)

[Deathwish]

all caps should be coloured like mullard ones.

[philpem]

all caps should be coloured like mullard ones.

They certainly looked prettier 

[ResR]

The tropical fish capacitors are quite nice indeed.

...Resistor codes used to be easy to read, now the colours look all the same...

I have 1990's resistors from old european origin tv where brown, red and orange all look the same on dark red background and brand new resistors with 4 bands that has the colors clear as day. It really depends on factory that makes these rather than age. Cheers for the multimeter from me too. 

[Psi]

i hate that tantalums break the convention and have a small line for positive.

[Zero999]

i have that tantalums break the convention and have a small line for positive.

All the tantalum capacitors I've seen have a line for the positive. I don't know why tantalum capacitors mark the positive and aluminium capacitors mark the negative. It's very retarded.