rtc test 2
joshua.clayton at uniwest.com
Wed Nov 18 09:38:03 PST 2015
> On Monday, November 16, 2015 09:46:33 AM Steve Eagan wrote:
> I agree, setting to the opposite extreme is a good idea
> On Friday, November 13, 2015 03:45:56 PM Joshua Clayton wrote:
> > rtc on 109 was set to the maximum adjustment value 273420 parts per
> > billion.
> > synchronized at 3:39:00 pm Today.
> > I'll check it again on Monday to see how far it has drifted.
> > Monday November 16 at 7:42:00 on my PC clock, the rtc on109 reads 07:40:36
> > My expectation was that the time would be ahead, instead it is 1 minute 24
> > seconds behind. Perhaps I misunderstand which way the adjustment pushes
> > the
> > clock?
> > On the bright side, the effect is pronounced. It seemws to support the
> > idea
> > that it is doing something.
> > Any thoughts on a value to try next? My first thought is to set to the
> > opposite extreme... Going ahead with that.
> > OK then. Setting adjust to
> > root at evi:~# cat /sys/class/rtc/rtc0/device/adjust
> > -277760
> > root at evi:~# cat /sys/class/rtc/rtc0/device/d
> > 0xc0
> > Monday November 16 at 7:51:00 Clock syncronized to my PC clock.
Tested rtc this morning
November 18 7:45:00 AM, instrument 109 shows November 18 7:45:03
So the adjusment has made the clock fast. The adjustment is in the opposite direction previously thought.
3 seconds * 1 billion / 172440 seconds = 17397 parts per billion
I am going to try another setting:
if the setting -277760 yields 17397....
I'm kind of in a boggle.
-277760 + 17397 would be -260363... the closest available value is -260400
synchronized November 18 09:33:00
root at evi:~# cat /sys/class/rtc/rtc0/device/d
root at evi:~# cat /sys/class/rtc/rtc0/device/adjust
Since my understanding of the math involved was upside down, I have little confidence in the above figures (except the empirical numbers),
but the testing will continue.
One thing to think about: The closer we get, the longer it will take to make a good measurement. Data is only available at one second
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