Electronic – “104” caps testing as 50-60 nF and their use as decoupling caps

capacitordecoupling-capacitor

I have a bag of capacitors labeled "104." (I don't recall their origin; probably an old AliExpress order.) However, they all test, on both my multimeter (a UNI-T UT61E) and a little microcontroller-based tester, as between 50 and 65 nF. I have another (clearly different in both colour and shape) "104" cap from another source that does test at around 93 nF, which makes me believe that I am testing them properly. (I do short the leads for a moment before checking the value.) But perhaps I'm not; am I missing anything here?

In case it helps, here's a picture of the caps in question: the two brown ones on the left are the seemingly 56 nF caps (front and back), and the one on the right is the actually-100 nF cap.

104-really-563-cap-on-left

If I am measuring the value right, are these caps damaged in some way or just mislabeled. If the latter, is this sort of mislabeling common when buying jellybean parts?

I no doubt bought these as decoupling caps for things like old 8-bit CPUs and their peripheral chips. What should I do with these?

  • Use a pair of them at each decoupling location to get the seemingly-standard 0.1 μf decoupling value.
  • Just use a single one because 50-60 nF will work fine? (They do seem effective at cleaning up, e.g. a 1 MHz waveforms when I check on my oscilloscope.)
  • Not use them at all because they're too dodgy?

Best Answer

I do short the leads for a moment before checking the value

Right start


If it is a breadboard PCB, i would put one or two in parallel and still go with it for a low voltage application 5V, 3,3 V.

Always buy components from reputed shops/sites.

  1. The tolerances will be +/- 20% for the general purpose capacitors
  2. for a decoupling application, the exact 100nF is not a must requirement
  3. if it is for a RF application or a safety application, you would not have even considered using the capacitors without the datasheet