[time-nuts] More ES100 WWVB Measurements

[paul swed]

Good detective work. Oren is who I used to talk with at everset.
Regards
Paul
WB8TSL

On Mon, Dec 31, 2018 at 4:32 PM Joseph Gwinn <joegwinn at comcast.net> wrote:

> On Mon, 31 Dec 2018 12:00:02 -0500, time-nuts-request at lists.febo.com
> wrote:
>
> >  time-nuts Digest, Vol 173, Issue 44
>
> > Message: 7
> > Date: Mon, 31 Dec 2018 04:04:22 -0800
> > From: "Tom Van Baak" <tvb at LeapSecond.com>
> > To: "Discussion of precise time and frequency measurement"
> >       <time-nuts at lists.febo.com>
> > Subject: Re: [time-nuts] More ES100 WWVB Measurements
> > Message-ID: <96BB388753294278A9CDE96C1EA7D9AE at pc52>
> > Content-Type: text/plain;     charset="UTF-8"
> >
> > Hi Graham,
> >
> > That's very nice work. And you have uncovered several unusual effects
> > in the ES100. Bugs? Features? If we time nuts keep up the good work
> > to evaluate this chip, we are likely at some point to get an
> > informative response from the guys who designed it. They read
> > time-nuts.
>
> I didn't see this mentioned, but I think I have found the relevant US
> patent application: US20130051184A1, Real-time clock integrated circuit
> with time code receiver, method of operation thereof and devices
> incorporating the same, Oren Eliezer et al, Oren Eliezer et al, filed
> 2013-02-28.
>
> .<https://patents.google.com/patent/US20130051184>
>
> Found this by chasing stuff from the EverSet website:
> .<
> http://everset-tech.com/wp-content/uploads/2014/11/ReceiverRadioClocks.pdf
> >.
>
> Joe Gwinn
>
>
> > So now both you and Tim have observed the off-by-one-second (or
> > off-by-N-seconds) effect in the ES100. I wonder if this explains why
> > some of my ES100-based La Crosse 1235UA Ultratomic wall clocks are
> > off by a second sometimes.
> >
> > My main question: in your "Time Plot.PNG" plot, what is the cause of
> > the sawtooth pattern? The points are almost all on a clear negative
> > slope, though bounded by roughly +/- 75ms. Looking on the far left, I
> > see a time drift of +50 ms to -25 ms over an hour, which is
> > equivalent to a -20 ppm frequency offset; about -2 seconds/day.
> >
> > Do you think this is due to the 16 MHz onboard xtal? If so, how about
> > changing the temperature of the eval board by a lot (say, several
> > tens of degrees) for an extended time (say, 4 hours) and see if the
> > sawtooth slope changes convincingly.
> >
> > Also, just to be sure, can you put a known independent timing signal
> > (e.g., GPS/1PPS) into your complex BeagleBone Black / Debian 9.4 /
> > ntpd time server / Python 3 / Excel stack to establish the validity
> > of your measurement methodology? Very likely you did it right, but I
> > always cringe when I hear "Linux" or "NTP" and "precise time" in the
> > same sentence. Yes, sorry, forgive me; I grew up in the "trust, but
> > verify" generation [1]. It applies pretty well to metrology also ;-)
> >
> > /tvb
> >
> > [1] https://en.wikipedia.org/wiki/Trust,_but_verify
> >
> >
> > End of time-nuts Digest, Vol 173, Issue 44
> > ******************************************
>
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