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Yageo's SMT capacitor datasheet lists the ESR vs. Frequency Curve show below:

enter image description here

Note that impedance (Z) is listed in units (W). How can this be understood? Why is impedance seemingly not measured in Ohms, as is customary?

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  • \$\begingroup\$ Does this answer your question? What is impedance? \$\endgroup\$ – tuskiomi Feb 3 at 7:36
  • \$\begingroup\$ it's a very common inter-character set typo error, you get used to seeing it. \$\endgroup\$ – Neil_UK Feb 3 at 7:39
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W just means \$\Omega\$, so Ohms.

The small letter omega: \$\omega\$ looks a bit like a "w".

It is possible that a "W" was typed at the Y-axis of the graph but that this wasn't converted into the Greek character \$\Omega\$ when the pdf file was made.

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  • 1
    \$\begingroup\$ This is a very common error seen in many datasheets, most likely a general issue with fonts or other parts of the process making the PDF. It does not take long before brains start to auto-correct that. \$\endgroup\$ – Justme Feb 3 at 7:39
  • \$\begingroup\$ Omega maps to W in Windows Symbol font (IIRC), so it's likely that at some point a font substitution was made and "Symbol" was replaced by an ordinary font. These day there are better ways of inserting Greek letters but old methods are often still used \$\endgroup\$ – Chris H Feb 3 at 16:46
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In addition to Bimpelrekkie's answer:

I wonder if it is a conversion error by PDF. The µ from µF is converted correctly. So, probably, the tool to make the graph didn't support Greek letters and therefore the author decided to use a letter coming closest to the Ω.

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  • \$\begingroup\$ That or the author didn't double check when they generated the graph (as an embedded image) and that contained the non-converted "Ω", while actual text such as the legend up top with the proper Greek "µ" as originally entered came across just fine because Acrobat is capable of dealing with Greek characters and other oddities like that. \$\endgroup\$ – Doktor J Feb 3 at 16:01

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