rtc test 2

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:

quoted

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
0xc4
root at evi:~# cat /sys/class/rtc/rtc0/device/adjust 
-260400

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
granularity 

-- 
Joshua Clayton
Software Engineer
UniWest
122 S. 4th Avenue
Pasco, WA 99301
(509) 544-0720