I recently bought a capacitor assortment and am confused about the values. The chart below lists the capacitors and their values as is advertised on the web page on ebay. The ufd values seem to make sense but not the pfd values. According to two different sites with either a table or a calculator the markings should indicate the following values:
100 = 10pfd
221 = 220pfd
471 = 470pfd
The 100 and 221 above codes and values don't match the chart below.
As far as the codes of 10 and 47, I can't find any information as to what values those codes represent. The characters printed on the capacitors do match the numbers under the 'Code' column. Can any of you experienced fellas straight this out (if need be)? - Scotty
The only one that's wrong is the one marked 221, this will be a value of 220pF.
The last digit if it exists is the number of zeros to place after the two digits, and the value is in pF.
Thanks for responding. Shouldn't the one listed as coded 100 be a value of 10 with 0 zeroes, making it a 10 pfd capacitor? To be a 100 pfd capacitor shouldn't it be coded as 101? What are the pfd values of the ones listed as 10 and 47? They are marked as shown below. The 'J' is tolerance correct? - Scotty
If you have a smart phone there are some great free reference apps for these sorts of things. They are mostly good when you need your PC screen for other things.
The capacitor with the black top is an Asian 10PF NP0 capacitor and the one marked 47 J is an old Centralab 47 PF type J material which isn't real temperature stable and typically used for non critical coupling tasks typically used for radio frequency coupling task's
I'm pretty darn certain that 100 = 100pF and not 10pF, but 221 and 471 are
220 and 470 pF. Inconsistent, as it may seem. Anything under 100 pF will
just be the number stamped. 10 = 10pF, 47 = 47pF.
Yeah, for those <1000pf, sometimes the actual value is written on rather than the encoded value. So 100pf can be either 100 of 101. The latter of the two is correct according to the specifications, but I have seen the former used before.
I've never been able to fathom why the capacitor industry is so alergic to the nano prefix so adopted this resistor-colour code like scheme, despite the fact its as easy to print a letter as a number, and despite nanoseconds presenting no difficulties to electronics manufacturers!
So the strangeness of printing 0.001uF instead of 1nF, or 100,000pF instead of 100nF. For resistor colour codes there is the limitation of the number of separate easily-distinguishable colours - none left for prefixes. For printing text on a flat surface there is no such limitation and adopting a number-of-tens digit leads to much confusion (and here ambiguity - is 100 100 or 10? I've seen 1000 meaning 1000 but it could also validly mean 100...)
Often wondered how a whole segment of industry can develop such an aversion. And its not just nano, its milli, people write 10,000uF instead of 10mF for no discernable reason (again this is never done for microseconds and milliseconds...) I feel there must be a historical reason for this.
Thank you all for your replies. It's clear to me now. Thanks, Tom, for the link to the code chart. I've got it bookmarked. While doing some searching for an explanation of capacitor codes, I read that some meters can read capacitance. Made me want to know if my Centech meter could. Yep, it can. I know Harbor Freight can sell some cheap stuff but I really like this meter.Easy to use, read, and very versatile. - Scotty
MarkT:
I've never been able to fathom why the capacitor industry is so alergic to the nano prefix so adopted this resistor-colour code like scheme, despite the fact its as easy to print a letter as a number, and despite nanoseconds presenting no difficulties to electronics manufacturers!
So the strangeness of printing 0.001uF instead of 1nF, or 100,000pF instead of 100nF. For resistor colour codes there is the limitation of the number of separate easily-distinguishable colours - none left for prefixes. For printing text on a flat surface there is no such limitation and adopting a number-of-tens digit leads to much confusion (and here ambiguity - is 100 100 or 10? I've seen 1000 meaning 1000 but it could also validly mean 100...)
Often wondered how a whole segment of industry can develop such an aversion. And its not just nano, its milli, people write 10,000uF instead of 10mF for no discernable reason (again this is never done for microseconds and milliseconds...) I feel there must be a historical reason for this.
Heck, I recall a distant past where schematics would only show caps having uF and uuF as the units of capacitance.
Speaking of caps... Will 24pf ceramic caps work in place of the 22pf in the ATMega8 (or 168, 328) Arduino circuit with the 16 MHz crystal? No one carries them locally & I have the 24pf's on hand. How much difference will it make. I also have 18pf & 10pf caps. I had thought about putting two 10pf caps in series x2 for the crystal, but that just looks very crowded. I guess, simply put, is there a suitable capacitor alternative for the 22pf caps for the 16 MHz crystal?
AptPupil:
Speaking of caps... Will 24pf ceramic caps work in place of the 22pf in the ATMega8 (or 168, 328) Arduino circuit with the 16 MHz crystal? No one carries them locally & I have the 24pf's on hand. How much difference will it make. I also have 18pf & 10pf caps. I had thought about putting two 10pf caps in series x2 for the crystal, but that just looks very crowded. I guess, simply put, is there a suitable capacitor alternative for the 22pf caps for the 16 MHz crystal?
Thanks,
AptPupil
Sure, 24pf will work. The effect of using padding caps of slightly different values then the crystal manufactures rated capacitance loading spec is that the frequency will be slightly offset from it's nominal marked value. In fact in some crystal oscillator designs one of the fixed padding caps is replaced by a small variable 'trimmer' capacitor so that the nominal frequency can be tweaked while being measured with a frequency counter or other indirect methods. Note that this kind of 'calibration' will not fix frequency error caused from variation in ambient temperatures.
Wow! I just remembered where I posted this question! LOL
Anyway, thanks for the replies. I did try the 10pfs & it worked. But, like I said, it looked crowded. Then, I remembered reading somewhere that people leave them out sometimes. So, I left the crystal in & removed the caps, & that also worked.
I made an RGB LED mood/night light for my daughter on a Radio Shack protoboard with an ATMega8 with the crystal & no caps. It works fine.
