[engi_nerd]

>You have no idea how hard it is to get Americans to use 100% metric everything, even in the year 2016 in a highly technical field.

American in a highly technical field here. I have no issues with using SI units when appropriate. But there is a tremendous lock-in, at least in some areas. Aerospace is a nasty mishmash, resulting in things like aircraft that "think" about altitude in feet, fuel in pounds, gear displacement in inches, but electric field strengths in W/m^2 and geopositioning in meters. All of those choices were made long ago, I'm stuck with them. My only defenses are to keep meticulous track of units and convert where necessary (while paying attention to things like numerical error).

[walrus01]

we are pretty much resigned to the fact that buying all of the pieces to build a datacenter/colo/telecom facility, everything is going to be in US customary units, because that's what the suppliers have. It's a vicious cycle of nobody in the US choosing to stock metric items, so nobody can buy it, and all of the end users just use things that are US units. It can be the smallest things like threaded rod uses to hang overhead fiber trays in a datacenter (all of the fasteners, bolts, nuts, the rod itself, etc) are all in US units. All the way up to the largest things like $150,000 generators where all of their specifications are in US units and fuel consumption figures in gallons, etc. If it involves the construction industry it's 99% of the time going to be US customary units.

We only get down to proper metric units when dealing with the fiber itself, but even that is lashed to aerial pole-to-pole strands, where the steel strand is in US units, all of the hardware is US.

The battery backup shelves for large AGM lead acid batteries: All US units. The batteries themselves are specified in inches and pounds. Once again it can all be converted, but that's the default unit from the manufacturer. Floor loading calculations? Pounds per square foot.

[jaclaz]

A related serious incident (mistaken units) in aerospace was the NASA Mars Climate Orbiter:

https://en.wikipedia.org/wiki/Mars_Climate_Orbiter

>However, on September 23, 1999, communication with the spacecraft was lost as the spacecraft went into orbital insertion, due to ground-based computer software which produced output in non-SI units of pound (force)-seconds (lbf·s) instead of the SI units of newton-seconds (N·s) specified in the contract between NASA and Lockheed.

[engi_nerd]

Yes, this is the kind of thing we have to zealously guard against. Formal specs for data exchange are very important!