Question: My sonicap gen1 1uF 200VDC capacitor's capacitance is measuring at .975. Does this mean it's faulty?
Thank for helping out a clueless drummer!
-Joe
Thank for helping out a clueless drummer!
-Joe
No It just means it is probably well within tolerance. Most caps are at least +- 10% tolerance, some are tighter. Unless the caps are rated 2% or better tolerance then it should be within spec.
Tony.
Tony.
For a 1uF, 10% rated cap, anything from 0.9uF to 1.1uF is within tolerance.
With film caps, the smaller values are cheaper to make, so they tend to be a little under
the nominal value, rather than over.
With film caps, the smaller values are cheaper to make, so they tend to be a little under
the nominal value, rather than over.
Also your capacitance measuring device also has a tolerance, which might be worse than the capacitor for all we know...
Well I thought I'd test this hypothesis in a small way. Dug out all the 100nF film caps in my stock, which happened to all be "104 J100" (ie 5% tolerance) and measured with a tweezer multimeter of uncertain spec (but definitely repeatable).
The caps were in three shades of yellow, indicating 3 different manufacturers.
I had 3 of the dark yellow, mean = 111.4nF, s.d. 0.1nF
I had 4 of the lemon yellow, mean = 100.7nF, s.d. = 0.72nF,
And 12 of the medium yellow, mean = 98.37nF, s.d. = 4.76nF (min 91.5, max 108.6)
So clearly the first point to note is that many were simply out of tolerance completely.... And the worst offenders were _over_ value by 11% but very close in value (yes 3 is a small sample, but they were matched to 0.1nF...)
The medium yellow had the worse spread by far though, arguably more important.
However uncertainty in the measurement device might be misrepresenting things a little, but the overall spread of 91.5 to 111.5nF is clearly more like 10% than 5%.
Some of these are undoubtedly eBay purchases, if not all, generic stock for tinkering, likely PP. Not sure I have large sets of caps with good provenance, I tend not to over-order film caps for building pcbs as they are not prone to failure.