Alain said:
The computer is generally kept on at all times. The computer is also
generally not connected to the internet, allowing synching with an NTP time
server impossible.
When I saw this happening in front of my eyes, I quickly opened a command
prompt and typed in "time". As I understand it, this is the BIOS time so can
be different from that reported by Windows, right? Anyway, this showed the
same time as in the notification area, bottom right of Windows XP, so now I
don't know what to think.
Is there any hardware, even if it costs lots of money, that can be
implemented on these machines to get a more guaranteed clock performance?
These machine are used in high speed production lines and timing for
rejection is critically important!
Thanks,
Alain
You can get GPS based solutions. We installed one at work, and the installation
required an antenna to be placed on the roof. (The office building has too many
RF issues, to do otherwise.)
This is just the first one I found in a search. That doesn't mean it's the best
or the cheapest. And GPS doesn't even need the onboard crystal oscillator.
If your computers had serial ports, you might just use an "ordinary" GPS
and get the time from it. GPS receivers deliver status messages once
per second, and time keeping is a function that comes out of it.
http://www.atomictimeclock.com/stsystarcard.htm
This is an example of rolling your own, using a regular GPS with RS232
interface. (Some GPS now come with USB, but inside, there might be
a USB to RS232 conversion chip. The tech is that old and slow, to not
need to be native USB. The provision of USB on modern ones, is
because computers no longer have RS232.)
http://time.qnan.org/#hw-inventory
If the computer with the clock card is networked with a LAN cable,
then the clocks in the other computers can be sync'ed to it (use a
version of NTP, other than the one in Windows). I'd start with the purchase
of just one card, and see if the performance is good enough (via LAN synchronizing),
to suit all machines.
*******
GPS time pieces can come as simple add-in cards, or the GPS can be used
to do more than run a very nice wall clock. I think the one we had installed,
had something to do with setting up a lab reference clock source. That
would be bussed to lab equipment, to give them an accurate 10MHz input reference.
(That allows things like frequency counters, to be bang on, by using
an external 10MHz input reference. Of course, there are other instruments
that use a 10MHz external input as well, like perhaps spectrum analyzers.
You run coax around the lab, to distribute the reference.)
The GPS makes it all traceable to atomic clocks (tracking drift and
adjusting output frequency). This is a project along those lines. We
couldn't have justified the antenna on the roof, just to more
accurately predict "time for coffee break"
Although, the
instrument did display local time for you, to some number of
digits.
http://www.jrmiller.demon.co.uk/projects/ministd/frqstd.htm
Ours had a fancy status display on the front, and it would tell
you how many satellites it could see and so on. I wouldn't want
to guess at the price. Some of the instruments in the lab cost
$250,000, so whats $10K here or there ?
I don't think the solution has to be that expensive - expect
to be gouged by your vendor, if you're in a hurry.
Paul
