Cap codes

[Vetsen]

OK, I have a question, I have a film type cap that says "Mial 390h" So is this 39pf? Or is it 390nf or 390pf? I know that Mial was a quality cap manufacturer.

Vetsen

 

[NewYorkDave]

Most likely 39pF, and the "H" refers to some aspect of its construction, voltage rating, etc.

The convention for cap marking is first digit/second digit/multiplier, just like the colored bands on a resistor. But the unit is pF. For instance, I have a number of 0.1uF, 400V film caps, and they're labeled "104k." 0.01uF caps from this series would be "103K", and so on.

 

[Vetsen]

So I took a few caps to my work an measured them with an LCR meter. Turns out that 390 is 390pf. I set the meter to it's lowest setting and measured a "121" ceramic cap. Reading: 119pf then the mial poly "390h" Reading: ~390pf.

Just wanted to follow up on this.

Steven

 

[NewYorkDave]

Yeah, your cap had a nonstandard marking. It's good that you checked it. If it had followed standard practice, it would've been labeled "391."

(3, 9, and one zero).

the markings on your 120pF cap follow standard practice.

 

[gyraf]

390pF can be written either "390" and "391" - they're both correct. There's no confusion with the last zero, as the "zero-counting" does not include zero zeroes (sic..!). A 39pF would simply be labeled "39"

Jakob E.

 

[NewYorkDave]

Yeah, you would think, but I've actually seen some caps where the zero meant just that... "zero zeroes!" After all, they do start the multiplier count at zero in the case of resistors, and the code used on caps grew out of that. (Some old caps had colored bands instead of printed numerals).

The great thing about standards is that there are so many of them :wink:

When in doubt, always measure.

 

[CJ]

:guinness: