[time-nuts] purpose of time of day display units

Chris Albertson albertson.chris at gmail.com
Sun Jan 22 14:26:48 EST 2017

I used to work at a place that used a lot of those LED time displays that
were hooked up to IRIG.   Why were they there?  Because everyone hates to
toss out nice working equipment.  The displays were bought ages ago and
still work just fine.     Many of those racks you see were assembled 15 or
more years ago.

Today my cell phone has a time display that is just as accurate as a GPS
controlled LED display because the bottle neck for displays is human
perception, We just can't see better than about 1/20th of a second.

Sometimes however we'd run the equipment with the time of day not set to
the actual time of day, say for re-playing historic data.  THEN the display
is nice to have if for nothing else to verify the setup is working and you
are in fact sync's up to recored IRIG from some 20 year old database or
even tape.    But even for real time, the display verifies the system is
running.  If it matches your iPhone then all is good.

In short the best use of these displays is confidence that things are
working.  Because you know they display is driven by IRIRG and not by a
realtime clock, so if you are getting IRIG data, you are up and running to
at least some degree.

On Sat, Jan 21, 2017 at 10:31 PM, Ruslan Nabioullin <rnabioullin at gmail.com>

> Hi, looking at pictures of various time metrology equipment setups for
> best practices and inspiration, I have commonly seen time of day display
> unit(s) installed in racks containing processing or time transfer
> equipment, e.g., http://www.xyht.com/wp-content/uploads/2015/05/Powers_
> Master_Clock.jpg. All that these units do is merely display the time of
> day and sometimes the date, typically by means of seven segment LED
> displays, of the time code inputted to them (typically IRIG-B, I'm
> guessing).  Any ideas why such a unit is necessary when one can simply look
> at the time displayed by timing receivers and time code generators (and
> even some standards), and the interface of some fusor, defined in this
> context as a system which performs timing data fusion (by implementing a
> paper clock or a more primitive algorithm) and timekeeping, either by means
> of a direct shell, or via something like NTP?
> Thanks in advance,
> Ruslan
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Chris Albertson
Redondo Beach, California

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