----- Original Message -----
From: "Rob Seaman" <[EMAIL PROTECTED]>
To: "Leap Second Discussion List" <[email protected]>
Sent: Monday, March 31, 2008 10:43 AM
Subject: Re: [LEAPSECS] operational time -- What's in a name?
Clive D.W. Feather wrote:
Tony Finch said:
So you think that the millions of existing radio controlled clocks and
watches should stop showing civil time?
They already do.
Case in point: When the local Red Cross center relocated a couple of
years ago, new RC "atomic" clocks appeared over each blood donor station.
[snippage]
Rather, a clock that claims extreme accuracy (through overtly extreme
precision) must ultimately be layered on a well designed system of
traceable time signals. RC time signals are meaningless (no matter the
underlying timescale) if the logistical issues (as described by Steve,
for instance) are ignored. Logistics keys on developing a coherent model
of the system being operated.
It is not enough to simply create a single perfect clock. The perfect
clock demands a matching distribution protocol. The ntpwg mailing list
makes interesting reading if one is tempted to believe this is a solved
problem.
What kind of clock does the Red Cross require? Focus on the use cases,
not the technology.
Rob Seaman
NOAO
It surprises me that the Red Cross needs this kind of accuracy to begin
with. The only reason a blood bank would need reasonably accurate clocks is
that the units collected have to be used within 72 hours according to
regulations, or so I've read. Surely at least a few minutes leeway is
allowed, and NIST-traceable accuracy is overkill. (Commendable overkill,
sayeth the anal-retentive geek side of me, but overkill nonetheless.)
FWIW, blood banks are usually located in buildings with _lots_ of
fluorescent lights. Good luck getting a radio-controlled clock to work in
an environment like that.
Brian Garrett
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