what is "tau"?

what is tau

hi

what is "Tau" ?
few times I heard some people use tau instead of milimeter or micrometer or mil for trace width or dielectric thickness specification.

what is tau?

Tau is used to represent the time constant. Apparently, you've seen it discussed in relation to the propagation delay along a track. Track width, length, resistivity, and the dielectric constant of the media surrounding the track all would affect Tau (the time constant).

what is tau?

is it relative to something, or a fix constant, like 24.238463486 ps ?
the people talking about it dont know too much about resistivity and dielectric constant...
it was something like "ok, set the trace width to 3 tau", or something like that.

inch tau mil

"Tau" or "Thou" in context you describe is slang expression for one thousandth and it refers to units in inches. "Mill" is same that comes from "milli" used in SI system and is also refering to 1/1000 of inch. "Thou" is more used in machining, while mill is more used in design of PCB's. In essence, just stupid sleng that improperly uses measurement units, because some people are to lazy to pronounce "milli inch" or "one thousandth of inch".
Another stupid one to watch for is "micron". In order to know which unit speaker refers to, you have to clarify if he is referring to "micro inch" or "micro meter". If you are trying to clarify dimensions on project for your company machinist, you might get empty stare as they might never new that "Micron" could mean something else other then micro-inch.

microinch stupid

so, the thou is same as mil, which is milli-inch ?
some people started using thou, probably just to confuse me. they used to use mils or milimeters when talking to me in project meetings. of course i didnt ask them what it is, i didnt want to give that victory for them.

thanks.