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Capacitor Value

9/10/1999 8:23 PM
Jason Borders
Capacitor Value
Would someone know where I could find a chart or tell me the value of a 100V mylar capcitor marked 685K. Thanks for any help.
9/10/1999 8:28 PM
.68 uF  
I'll let someone else post how to read the value.
9/10/1999 8:44 PM
Jim S.

I get 6.8uF.  
Here's how I got it:  
Take the first two digits and append the number of zeroes (or "zeds" for you Brits out there) given by the third digit. This gives me 6800000. This is the number of pico farads (pF). To get microfarads (uF), divide this number by 1 million. This gives me 6.8uF. To get the less-commonly-used nanofarads value (nF), divide by 1000:  
6800nF. I would guess this is a physicaly large cap!!
9/11/1999 12:00 AM
O.K., I see where I went wrong. I used a 'mantissa' of 6.8 (instead of 68)followed by 5 zeros, so I was low by a factor of ten. This is yet another example of how using scientific notation ruins your brain.  
I've always had trouble with reading these codes, so I have a table taped to my oscilloscope with a few examples, like  
220 = 22 pf (almost always seen as simply '22')  
331 = 330 pF  
472 = .0047 uF  
333 = .033 uF  
564 = .56 uF  
105 = 1.0 uF  
I always refer to it whenever I run across one of these caps, but unfortunately, I'm not around my oscilloscope today.
9/10/1999 8:33 PM

Ok, I'll do the "someone else" bit....  
Take the first two numbers, add the amount of zeros to the end as specified by the third number (5 zeros in this case) and you have it's value in picofarads.  
Divide that by 1000 to get nanofarads, and by 1000 again to get microfarads (ufs).  
... Whit  
9/10/1999 8:46 PM
Gil Ayan

"Would someone know where I could find a chart or tell me the value of a 100V mylar capcitor marked 685K. Thanks for any help."
Oops, moocow slipped I think... Last digit is the power of 10, in this case 10^5 in pF, so you get 68 x 10^5 pF, which is 6.8uF.  
9/11/1999 12:08 AM

I'll add the last bit of trivia. The k stands for the tolerance, which is +/- 10%.  
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