[LEAPSECS] operational time -- What's in a name?

[Rob Seaman]

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.

- With an 8 week sampling interval, I can report that for the first  
six months or so, the clocks were synchronized to the radio with low  
dispersion.

- Around the six month mark (say, around the time DST changed for the  
first time), the dispersion kicked upward for several of the clocks  
but most remained synchronized.

- Around the one year mark it was about half and half - that is, it  
looked like half the clocks were now running open loop.  Presumably  
batteries were changed, etc.

- At 1.5 years, the Red Cross introduced a new hand held data entry  
device for scanning bar codes from the bags, etc.  This has a printer  
such that much less data is handwritten.  The device also appears to  
include its own clock (perhaps synchronized across the system).  The  
wall clocks seem to fill a purely utility purpose now.

- After two years, the clocks are all off the grid with no two  
synchronized.

Each system we design and use has unique relative and absolute  
timekeeping requirements.  It is hard, however, to see any problem for  
which the current generation of consumer RC clocks is an appropriate  
solution.  Ease of setting is a great feature.  But setting a clock  
also involves checking that you set it correctly (selected the right  
combination of buttons on the back).  Precisely by advertising such  
clocks as whizbang atomic clocks, the user community will relax their  
own vigilance (never much to begin with).

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