>From your first reference, I did the calculation for the 42U (internal
depth).
If we assume the module size confirmed by Chris (45 mm) and do the metric
calculation (42 x 45 mm) and a metric conversion from the inch
specification, there is a discrepancy of 9 mm -- which would be critical.
The first calculation yields a value of 1890 mm. The second yield a value of
1899 mm (rounded from 1898.65).
I guess, for 1U equipment (1.75"/45 mm), the discrepancy is trivial.
However, for 42U and other high multiples, the cumulative discrepancy would
be unmanageable.
So, I guess we have to go with a soft-metric figure of 44.45 mm (which is
exact). Rounding to 44.5 would produce too great a cumulative error for
large devices or front panels.
On the other hand, 19" could probably be converted to a rounded 483 mm (from
482.6 mm), as cumulative error isn't a factor for rack widths. I'm assuming,
of course, that the tolerance isn't smaller than about ?0.8 mm. (Does
anyone know for sure?)
Thanks, Ian and Chris.
Bill Potts, CMS
San Jose, CA
http://metric1.org [SI Navigator]
> -----Original Message-----
> From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On
> Behalf Of i.moseley
> Sent: November 05, 2000 14:21
> To: U.S. Metric Association
> Subject: [USMA:9010] metric standards and eia-310
>
>
> You may need to check the line wrapping on these links. I've had to go
> to full screen to get them on one line each.
>
>
> >
> http://www.cst1inc.com/soc/digital_servers/Digital_Server_Rackmoun
> t_Cabin/digital_server_rackmount_cabin.html
> This seems to show the standard being irrational in all systems of
> measurement (or perhaps I'm just being cynical).
>
>
> >
> http://esone.web.cern.ch/ESONE/Syscomms98/slides/23SS/Standards/ts
> ld007.htm
> This refers to an iec standard in hard metric.
>
>
