Windows NT and System Clock Accuracy

  • Thread starter Juan De los Santos Naumov
  • Start date
J

Thread Starter

Juan De los Santos Naumov

We've an application running on Windows NT SP6.0. We need to log events with a time stamp, but we are facing a problem with the system clock. We can't make the clock on windows NT shows the same time of the computer RTC. We adjust the time in Windows but after few hours the time have a delay compared with the RTC.

Any body have an idea?

Thanks a lot

Juan De los Santos
 
F

Fernando Gomes

The problem is that the NT clock acuracy depends on the motherboard/crystal accuracy, and it might be not good enough for you.
I have made a software tool that uses a operating system function called AdjustTime. We can input the 'real' drift (we have to measure the drift),
and it adjusts the clock speed. We have to call this tool on every system startup.
If you need some more information please let me know.

Fernando Gomes
 
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Randy DeMars

I ran across a similar situation once. In my case I never looked at the system clock, so I don't know if it was the different than the NT clock, but the NT clock was changing itself. I would set it with one of the automated clock setting utilities that get the time over the internet. After several hours the time would be off by a certain amount, and always the same amount. What was causing this was an NT service that was synchronized the clock with that of the server. I stopped this service and the clock stayed as set.
 
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Lunnon, Robert

Probably the best idea for time-stamping is to synchronise all your network clocks. You can use the open source ntp software for this (a google search should find it). Your local master node can be synchronised to an internet clock master or to a local time reference such as a GPS receiver. The slaves can be synchronised to the master either using the ntp software (xntpd) or
via Micro$ofts arrangements (if you use their software). If you do this you should get performance at the millisecond level to an absolute reference which should ensure that events are at least in the right order.

Usually though only relative time is important, so you can simply synchronise the slaves to a single master time-server using the masters
local clock. While this will drift in an absolute sense at least all the computers have the same concept of time as the master computer (if not the
humans around them).

Bob

 
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Pravin Fatnani

What are the solutions available to keep the clocks of all NT workstations in a network synchronised? Is there any time server available which does this? There must be corresponding program to run in each workstation also.

Some one must have the idea?
Thanks a lot !

Pravin
 
Robert Lunnon:
> Probably the best idea for time-stamping is to synchronise all your
> network clocks. You can use the open source ntp software for this
...
> Usually though only relative time is important,
...

If you have (at least intermittent) access to the Internet, you can synchronise the local master using that. There's public and semi-public NTP
servers around, just pick a couple of appropriate ones nearby (ask your ISP, or just try substituting "ntp" for "www" in their domain name).

That'll also make sure you have the timezone set right, because NTP runs on UTC (the old Greenwich time).

Jiri
--
Jiri Baum <[email protected]>
http://www.csse.monash.edu.au/~jiribvisit the MAT LinuxPLC project at http://mat.sf.net
 
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Ranjan Acharya

Clock synchronisation on NT involves either paid-for for free tools.

Every one has their pet synchronisation tool for NT. We have used AboutTime from http://www.arachnoid.com/. A site full of useful (sometimes dated) tools -- also has a detailed explanation of exactly why the sky is dark at
night.

Their AboutTime tool works quite well. You can set up any machine to be a time server with other machines reading it and go from there. You do not
have to access the Internet, just pick a machine with an accurate clock. We have also used a master machine to set the PLC RTCs too. It is a lot nicer if there is only one master clock in the system -- not just one on the PLC, one on the HMI, one on the SCADA et cetera. For plant that observe daylight saving time, it is even more of a pain since there can be dozens of clocks to set twice a year.

NT5/2000 has built in time management features, but I have never used them.

RJ
 
There are two items that you are talking about:

1. The first one is the Time synchronization server that you would put in your NT system.
Every machine must have a copy of this tool.
One acts as the master and other as slaves.
this helps in synchronizing the time within your network.

2. Next this same software allows you to synchronize with standard times
available on the internet.
It can do auto dial-up and synchronize your servers.

But before proceeding with time synchronization, ensure that the software's that you possess can handle time synchronization. Else you may end up with more problems.

Anand


 
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Peter Whalley

Pravin

There was a discussion on this in the list some months ago. Try searching on "COMM: Time synchronisation". My suggestion was:

Just run a command like:

net time \\server /set /yes

where "\\server" is the name of the reference NT server that the others sync to.

I run this in a bat file that resides in my StartUp directory in Win98 but it works in NT as well.

You could use the AT command in NT to run it at regular intervals. NT Help gives a basic overview.

Regards

Peter Whalley
 
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Vladimir E. Zyubin

Hello List,

Just a remark...

If you choose the internet solution, you have to be ready for the following events:
a) the timeserver is in shutdown,
b) the timeserver sends false time.

Good luck.
 
T

Tom Fenimore

We used an NT Server to time stamp data collected over an Ethernet LAN. We used a dedicated real time clock card that "took over" the clock on the
motherboard. It was extremely accurate within +/- 2-3 seconds per month. Search for one on the net. I'd tell you the name of the manufacturer, if I
could find the documents !
 
Vladimir:
> Just a remark...

> If you choose the internet solution, you have to be ready for the
> following events:
> a) the timeserver is in shutdown,

The machines will no longer be exactly GMT, but they'll still be synchronized with each other.

Besides, the NTP documentation spends a lot of time explaining how you should be running three time servers, each syncing agains three external
servers for a total of nine... Overkill, I say, overkill.

> b) the timeserver sends false time.

NTP has some provisions for avoiding this (see above), but yeah, you need to be careful. Still, with slewing, it'll be half an hour before you're a second off and well over a day before you're a minute off. If someone can attack you consistently over these kinds of timespans, you probably have bigger problems anyway.

Jiri
--
Jiri Baum <[email protected]>
http://www.csse.monash.edu.au/~jiribvisit the MAT LinuxPLC project at http://mat.sf.net
 
A

Alex Pavloff

The timeserver sends false time? Has that ever happened? I say this because there are loads "important" systems all running using NTP servers on the internet. Sure, there are many reasons why you might not be able to connect to them, but I don't think "false time" is a problem.

Using a program like Tardis for Windows, you can specify multiple time servers. Or you can always setup your own time server controlled by
yourself and using an external clock source, and have all your computers sync to that. NT's Timeserv works for this, as well as third party programs like TARDIS.
 
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Vladimir E. Zyubin

Hello Alex,

On Friday, September 28, 2001, 10:49:04 PM, Alex Pavloff <[email protected]SON.COM> wrote:

>> If you choose the internet solution, you have to be ready for
>> the following
>> events:
>> a) the timeserver is in shutdown,
>> b) the timeserver sends false time.

AP> The timeserver sends false time? Has that ever happened? I say this
AP> because there are loads "important" systems all running using NTP servers on
AP> the internet. Sure, there are many reasons why you might not be able to
AP> connect to them, but I don't think "false time" is a problem. [...]

Alas. I heard the rumor, that has happened already. During the first compaign against Iraq. As far as I recall, the USA's Time Service had "corrected" the time Iraq's missiles used... it has made them blind. BTW, that time was used by the europian allies as well... and they were not informed... because of an unfortunate inadvertence...

Really, I don't know, why MS can not solve this simple (IMO) problem in NT... but any conspirologist could say, to force us to use their timeservers. And again, where do the servers get the time from?

Generally speaking as a matter of fact, Internet makes life too unsafe... and instable. The ability to control has reduced to the knowledge of password (think, it is just a short sequence of chars)...

but all depend on the task, of course...

--
Best regards,
Vladimir
 
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