Bitten by SI units

The USA is one of a few countries that have not fully adopted SI units (sometimes called Metric units) of measurements across the board. Generally for people working in the USA on electronics projects it is a small issue. We quickly learn whatever translation is required. However, sometimes these units do cause problems when the same digits represent different objects.

I was just bitten by this with the footprint of a capacitor on a PCB I was having assembled. I read the data for the capacitor and saw the footprint was “0603”, so I searched my footprint library and dropped in a “0603” footprint. Unfortunately when assembly was attempted the capacitor was way smaller than the footprint. A few minutes of research revealed the issue, what I had used was an “0603” inch footprint, the part was “0603” mm.

Not sure how may other numbers like this exist in both measurement systems for capacitors and resistors, however you can bet that in the future I will be triple checking that!

Isn’t it about time the USA joined the majority of the rest of the world and fully adopted the SI unit system: