Using the HP 58503a to correct your PC clock
This has probably been covered in the past, but is there a way correct or control a PC (Windows 7) clock with the HP 58503A GPS receiver? I just bought one (on the way now) and have a copy of satstats50 on hand. I've been using Dimension 4 and I'm surprised at the size of correction every couple minutes to my PC clock. I'd be happy if my PC clock were accurate to plus/minus 100ms.
Ron
The WRONG way to adjust a PC clock is to set the TIME periodically from
some standard. When you do this then the time on the PC is not running at
a constant rate. The correct way to do this is to adjust the PC's clocks
RATE. You make it runs slightly faster if you notice it is getting behind
and slightly slower if it is running fast.
Think about what you would do to a real physical clock. You would not set
it every few minutes, you'd adjust the rate and wait a little while to see
if the adjustment needs refinement or not.
Most computers can run "NTP" what does this. In fact, using NTP you don't
need a GPS receiver to keep the clock to within a few milliseconds of UTC
as NTP will synchronize with other NTPs running on servers on the
Internet. Yes you can pull millisecond level time over the Internet. But
using a GPS receiver NTP can keep your PC's internal clock accurate at the
hundreds of microseconds level.
NTP is an interesting piece of software. With the very long delays over
the Internet you'd think you'd never be able to accurately transfer time
but you can get millisecond level accuracy even over a communications path
that has a 100 millisecond delay. The trick is to think about what you
would do if you lived in the 1700's (before the telegraph) and owned a
grandfather clock that was to big to carry and where given the task of
setting it to match a clock that was a ten minute walk away in a different
house. You best plan would be to first walk the round trip between the
two houses many times and measure the time it takes then add /2 the round
trip delay. Later you find that other neighbor own clocks so you start
making round trips to their houses too and keeping good notes on the trip
times between all the clocks. You could set everyone's clock based on the
consensus of other nearby clocks. Next you'd notice that some clocks are
just poorly made and you'd ignore these when building the consensus. This
is exactly what NTP does
Most operating systems in use today run NTP to keep their clocks in order.
Well most OSes except for Windows. Microsoft uses a vey much simplified
version of this that does the wrong thing and periodically sets the PC's
clock. You could enable this and likely, maybe reach your +/- 100ms goal.
Not the "real" NTP is a free program and not hard to set up so you can
have 1ms level accuracy without much effort and better with some work.
On Tue, Aug 2, 2016 at 8:13 PM, Ron Ott ronott@sbcglobal.net wrote:
This has probably been covered in the past, but is there a way correct or
control a PC (Windows 7) clock with the HP 58503A GPS receiver? I just
bought one (on the way now) and have a copy of satstats50 on hand. I've
been using Dimension 4 and I'm surprised at the size of correction every
couple minutes to my PC clock. I'd be happy if my PC clock were accurate
to plus/minus 100ms.
Ron
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--
Chris Albertson
Redondo Beach, California
This has probably been covered in the past, but is there a way correct or
control a PC (Windows 7) clock with the HP 58503A GPS receiver? I just
bought one (on the way now) and have a copy of satstats50 on hand. I've been
using Dimension 4 and I'm surprised at the size of correction every couple
minutes to my PC clock. I'd be happy if my PC clock were accurate to
plus/minus 100ms.
Ron
Ron,
Have you tried NTP?
http://www.satsignal.eu/ntp/setup.html
You may also be able to use the PPS output from your HP 58503a in
conjunction with a serial NMEA feed to sync your PC to much better than 10
ms, but NTP alone should be good enough for 100 ms if you have a
half-decent Internet connection. The only times we've seen issues have been
when the PC's motherboard clock is broken (drift more than 43 seconds/day in
NTP terms).
Some notes on using PPS with Windows may be gleaned here. Although the
device mentioned is no longer available, the general principles will apply.
http://www.satsignal.eu/ntp/Sure-GPS.htm
Cheers,
David
SatSignal Software - Quality software written to your requirements
Web: http://www.satsignal.eu
Email: david-taylor@blueyonder.co.uk
Twitter: @gm8arv
Hi
How big a correction are you seeing? Is the correction consistent?
Bob
On Aug 2, 2016, at 11:13 PM, Ron Ott ronott@sbcglobal.net wrote:
This has probably been covered in the past, but is there a way correct or control a PC (Windows 7) clock with the HP 58503A GPS receiver? I just bought one (on the way now) and have a copy of satstats50 on hand. I've been using Dimension 4 and I'm surprised at the size of correction every couple minutes to my PC clock. I'd be happy if my PC clock were accurate to plus/minus 100ms.
Ron
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To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
The old Tardis program for Windows (Tardis2000 now) handles it
correctly by altering the rate and only jamming the time if it is
outside of a specified window but I do not think its GPS mode supports
the 1 PPS signal.
I am not sure if Tardis works with Windows 7 and above though; I
forget to test it on my Windows 7 test system when I had it. It is a
pretty old (but free) program.
On Tue, 2 Aug 2016 23:28:06 -0700, you wrote:
The WRONG way to adjust a PC clock is to set the TIME periodically from
some standard. When you do this then the time on the PC is not running at
a constant rate. The correct way to do this is to adjust the PC's clocks
RATE. You make it runs slightly faster if you notice it is getting behind
and slightly slower if it is running fast.
Think about what you would do to a real physical clock. You would not set
it every few minutes, you'd adjust the rate and wait a little while to see
if the adjustment needs refinement or not.
...
Most operating systems in use today run NTP to keep their clocks in order.
Well most OSes except for Windows. Microsoft uses a vey much simplified
version of this that does the wrong thing and periodically sets the PC's
clock. You could enable this and likely, maybe reach your +/- 100ms goal.
Not the "real" NTP is a free program and not hard to set up so you can
have 1ms level accuracy without much effort and better with some work.
On Tue, Aug 2, 2016 at 8:13 PM, Ron Ott ronott@sbcglobal.net wrote:
This has probably been covered in the past, but is there a way correct or
control a PC (Windows 7) clock with the HP 58503A GPS receiver? I just
bought one (on the way now) and have a copy of satstats50 on hand. I've
been using Dimension 4 and I'm surprised at the size of correction every
couple minutes to my PC clock. I'd be happy if my PC clock were accurate
to plus/minus 100ms.
Ron
My granddaughter would love to know I have a Tardis program. (-;> Lots of things to try here, just to get a more accurate clock. No wonder there's a time-nutz group!
From: David <davidwhess@gmail.com>
To: Discussion of precise time and frequency measurement time-nuts@febo.com
Sent: Thursday, August 4, 2016 11:47 AM
Subject: Re: [time-nuts] Using the HP 58503a to correct your PC clock
The old Tardis program for Windows (Tardis2000 now) handles it
correctly by altering the rate and only jamming the time if it is
outside of a specified window but I do not think its GPS mode supports
the 1 PPS signal.
I am not sure if Tardis works with Windows 7 and above though; I
forget to test it on my Windows 7 test system when I had it. It is a
pretty old (but free) program.
On Tue, 2 Aug 2016 23:28:06 -0700, you wrote:
The WRONG way to adjust a PC clock is to set the TIME periodically from
some standard. When you do this then the time on the PC is not running at
a constant rate. The correct way to do this is to adjust the PC's clocks
RATE. You make it runs slightly faster if you notice it is getting behind
and slightly slower if it is running fast.
Think about what you would do to a real physical clock. You would not set
it every few minutes, you'd adjust the rate and wait a little while to see
if the adjustment needs refinement or not.
...
Most operating systems in use today run NTP to keep their clocks in order.
Well most OSes except for Windows. Microsoft uses a vey much simplified
version of this that does the wrong thing and periodically sets the PC's
clock. You could enable this and likely, maybe reach your +/- 100ms goal.
Not the "real" NTP is a free program and not hard to set up so you can
have 1ms level accuracy without much effort and better with some work.
On Tue, Aug 2, 2016 at 8:13 PM, Ron Ott ronott@sbcglobal.net wrote:
This has probably been covered in the past, but is there a way correct or
control a PC (Windows 7) clock with the HP 58503A GPS receiver? I just
bought one (on the way now) and have a copy of satstats50 on hand. I've
been using Dimension 4 and I'm surprised at the size of correction every
couple minutes to my PC clock. I'd be happy if my PC clock were accurate
to plus/minus 100ms.
Ron
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
On Thu, 4 Aug 2016 19:05:13 +0000 (UTC), you wrote:
My granddaughter would love to know I have a Tardis program. (-;> Lots of things to try here, just to get a more accurate clock. No wonder there's a time-nutz group!
The Tardis log shows that accessing external NTP servers is a problem
for me so I was going to setup a local server using a Garmin 18x but
during tests, a squirrel chewed the cable through and stole it.
http://www.mingham-smith.com/tardis.htm
2016/08/04 08:06:29.58
Correction of 0.071 seconds used to adjust clock frequency
2016/08/04 09:18:29.97
Correction of -0.102 seconds used to adjust clock frequency
2016/08/04 10:28:29.78
Correction of 0.220 seconds used to adjust clock frequency
2016/08/04 11:34:31.95
The time has been corrected by 1.431 seconds (Clock stepped)
2016/08/04 12:32:32.08
The time has been corrected by -2.206 seconds (Clock stepped)
2016/08/04 13:14:32.22
The time has been corrected by -1.588 seconds (Clock stepped)
2016/08/04 13:24:32.73
Correction of -0.377 seconds used to adjust clock frequency
2016/08/04 13:34:32.82
Correction of -0.374 seconds used to adjust clock frequency
2016/08/04 13:44:32.78
Correction of -0.225 seconds used to adjust clock frequency
David wrote:
I am not sure if Tardis works with Windows 7 and above though; I
forget to test it on my Windows 7 test system when I had it. It is a
pretty old (but free) program.
About five years ago, after a lot of experience with Tardis under XP, I
worked for several weeks trying to get it to work under Vista. I never
succeeded, and it fatally corrupted the system. I had to wipe the boot
drive and start over.
Best regards,
Charles
That's encouraging!! I'm working on NTP and have no idea what's happening. The description says it takes over the PC clock, excluding other apps. I like the rate correction concept, but not if I lose my hair or have to wipe the drive.
Ron
From: Charles Steinmetz <csteinmetz@yandex.com>
To: time-nuts@febo.com
Sent: Thursday, August 4, 2016 1:08 PM
Subject: Re: [time-nuts] Tardis [WAS: Using the HP 58503a to correct your PC clock]
David wrote:
I am not sure if Tardis works with Windows 7 and above though; I
forget to test it on my Windows 7 test system when I had it. It is a
pretty old (but free) program.
About five years ago, after a lot of experience with Tardis under XP, I
worked for several weeks trying to get it to work under Vista. I never
succeeded, and it fatally corrupted the system. I had to wipe the boot
drive and start over.
Best regards,
Charles
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
I always wonder why people try all kinds of solutions when there are two
known to work as well as theoretically possible.
There is NTP and PTP.
NTP was released to the world in 1985, about 30 years ago. The algorithm
has been in peer reviewed papers and the source code gets reviewed
continuously by experts in the field and when one of them finds a problem
solutions are discussed and corrections are made. After 30 years of
continuous review and revision it is close to as good as it will get.
(except for possible security issues in the implementation) There is a
very active community of academics and computer scientists that keep NTP up
to date. Its problem is that it is designed to work over a public
network that the user has no control over so the assumption must be made
that the network equipment has only some minimum features. NTP's accuracy
tops out (with great effort) at about 1 microsecond but typically 1
millisecond
PTP on the other hand is designed to do about the same as NTP but over a
local network the user has complete control over and requires specialized
networking equipment. PTP accuracy routinely breaks 1uSec but can't work
so well over a public Internet.
If these two where not free, easy to set up and well supported then it
might be worth looking for something else.
From a "Time Nuts" point of view none of the above are even close to
accurate clocks. A microsecond is a very course and crude measure of
time. Pico and Femto seconds are were it gets interesting.
Maybe someday NTP will have a time nuts level of accuracy. the new up
coming version, I hear will be using 64 bits to carry the factional part of
a second. That is truly nuts.
Yes, there is room for more software if maybe one needs to transform time
under conditions not covered by NTP or PTP or needs to do much better than
1uSec. But typically when that happens we resort to hardware solutions
like 1PPS distributions and/or 10MHz distortions or common view of GPS
carriers signals. Packetized network just don't work if you need to be
much better than 1uSec.
On Thu, Aug 4, 2016 at 11:47 AM, David davidwhess@gmail.com wrote:
The old Tardis program for Windows (Tardis2000 now) handles it
correctly by altering the rate and only jamming the time if it is
outside of a specified window but I do not think its GPS mode supports
the 1 PPS signal.
I am not sure if Tardis works with Windows 7 and above though; I
forget to test it on my Windows 7 test system when I had it. It is a
pretty old (but free) program.
On Tue, 2 Aug 2016 23:28:06 -0700, you wrote:
The WRONG way to adjust a PC clock is to set the TIME periodically from
some standard. When you do this then the time on the PC is not running at
a constant rate. The correct way to do this is to adjust the PC's clocks
RATE. You make it runs slightly faster if you notice it is getting behind
and slightly slower if it is running fast.
Think about what you would do to a real physical clock. You would not set
it every few minutes, you'd adjust the rate and wait a little while to see
if the adjustment needs refinement or not.
...
Most operating systems in use today run NTP to keep their clocks in order.
Well most OSes except for Windows. Microsoft uses a vey much simplified
version of this that does the wrong thing and periodically sets the PC's
clock. You could enable this and likely, maybe reach your +/- 100ms
goal.
Not the "real" NTP is a free program and not hard to set up so you can
have 1ms level accuracy without much effort and better with some work.
On Tue, Aug 2, 2016 at 8:13 PM, Ron Ott ronott@sbcglobal.net wrote:
This has probably been covered in the past, but is there a way correct
or
control a PC (Windows 7) clock with the HP 58503A GPS receiver? I just
bought one (on the way now) and have a copy of satstats50 on hand. I've
been using Dimension 4 and I'm surprised at the size of correction every
couple minutes to my PC clock. I'd be happy if my PC clock were
accurate
to plus/minus 100ms.
Ron
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/
mailman/listinfo/time-nuts
and follow the instructions there.
--
Chris Albertson
Redondo Beach, California