this post was submitted on 08 May 2024
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And they aren't kidding around, modern high speed signals are so fast that a millimeter or less of difference in length between two traces might be enough to cause the signals to arrive at the other end with enough time skew to corrupt the data.
Edit: if you ever looked closely at a circuit board and seen strange, squiggly traces that are shaped like that for seemingly no reason, it's done so that the lengths can be matched with other traces.
A millimeter is huge in these situations. USB3 requires 5 mil tolerances, just over 0.1 mm. This scales with the inverse of data rate.
Electronics are so fast that we gotta take the speed of light into account. God help you if you put too sharp a bend in a trace, too ...
What is a mil in this context? I'm genuinely curious.
Probably one thousandth of an inch.
Ew.
Yes.
Hey thousands of an inch are the only part of our imperial system that actually makes sense
I've heard it referred to as 'thou' but not 'mil'
A couple old metrology equipment dated back from the 80s I still use calls them 'mil'. It's got dual dials for mil/mm. Gets me confused sometimes because the gauge can go down to couple millionths of an inch/couple 10s of nanometers.
LVDT for those curious.
Yeah, I’ve never heard of that before either. What I have heard of is either MOA or MIL reticles. In that context a Mil stands for milliradian, which is a representation of angle. That definitely doesn’t track with the post though.
And it's especially confusing for people who use sane measurement systems where "mil" is short for "millimetre", because it's just the start of the word. I think anyone that still insists on measuring things in thousandths of an inch should keep their own bespoke lingo too, and everyone else should steadfastly refuse to acknowledge "mil" in this context.
Correct.