PSN-L Email List Message
Subject: Re: Computer Timing Problems / Solutions
From: ChrisAtUpw@.......
Date: Wed, 27 Apr 2005 22:24:37 EDT
In a message dated 17/04/2005, lcochrane@.............. writes:
If there is no timing reference available for the A/D board you can use the
PC's
time. In this mode the A/D board requests the current time from the PC every
minute or so and uses this time for data time stamping. If the PC's time is
keep accurate with a program like NTP the overall accuracy can be +- 30 or
+-50 ms or about the same as WWV/WWVB.
With regard to the different time references. By far GPS is the best, if you
can find
a location for the antenna that will allow the receiver to see two or more
satellite most of the time. The cost of an OEM GPS receiver with a 1 PPS
signal is now below $100.00 USD. I am now selling the Garmin GPS 18
(http://www.garmin.com/products/gps18oem/index.jsp) for this price. This is
a very
nice receiver that works very will with my A/D board.
Hi Larry,
However, GPS is still the most expensive of the timing options at $140 +
carriage. You need a clear path to the satellites and the power requirements
of 100 to 185 mA are very high for battery / remote operation.
Given that the cost to use GPS keeps going down I not sure I see the need to
support WWV/WWVB any more. The other problem is these signals are only
available here in the States. Since half of my sales are overseas a lot of people
will not be able to use this feature.
May I ask that you reconsider the situation, please? You seem to have
overlooked the fact that the inexpensive WWVB type modules are available for
not only the USA, much of Canada and central America, but also for Europe and
Japan. Since the computer modules give a fully decoded time signal, it should
be easy to make your board timing automatically fail safe for power outages
and for automatic start up. The power requirements ARE designed for battery
operation.
Your WWV tone decoder timing is only widely available on one frequency
during the day and on another during the night and only in North America /
eastern Pacific. It is not a 'fit and forget' 24 hour timing solution, unlike
many WWVB type systems.
Commercial seismic software DOES often use VLF radio signals as
alternatives to GPS and on-line timing.
>> And with most of the PSN station having a full time Internet
connection nowadays they always have the option to use NTP etc as a time reference.
Not everyone CAN obtain a permanent network connection and from my
experience, you DO NEED to have access to a time set program which MODIFIES
(disciplines) your computer clock rate. A permanent line connection is an expense
which your customers do not need to have. I cannot obtain a second phone line,
even if I wished to pay the extra $290 / year line rental.
See _http://www.ntp-time-server.com/_ (http://www.ntp-time-server.com/) and
_http://www.galleon.eu.com/_ (http://www.galleon.eu.com/) for radio modules.
Regards,
Chris Chapman
In a message dated 17/04/2005, lcochrane@.............. writes:
<=
FONT=20
style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size=
=3D2>If there=20
is no timing reference available for the A/D board you can use the PC's=20
time. In this mode the A/D board requests the current time from the PC=
=20
every minute or so and uses this time for data time stamping. If the PC's=20=
time=20
is keep accurate with a program like NTP the overall accuracy can be +- 30=
or=20
+-50 ms or about the same as WWV/WWVB.
With regard to the different=
=20
time references. By far GPS is the best, if you can find
a location fo=
r=20
the antenna that will allow the receiver to see two or more satellite most=
of=20
the time. The cost of an OEM GPS receiver with a 1 PPS signal is now below=
=20
$100.00 USD. I am now selling the Garmin GPS 18=20
(http://www.garmin.com/products/gps18oem/index.jsp) for this price. Th=
is=20
is a very
nice receiver that works very will with my A/D board.=20
Hi Larry,
However, GPS is still the most expensive of the=
=20
timing options at $140 + carriage. You need a clear path to the satellites a=
nd=20
the power requirements of 100 to 185 mA are very high for battery=20=
/=20
remote operation.
<=
FONT=20
style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000=20
size=3D2> Given that the cost to use GPS keeps goin=
g down=20
I not sure I see the need to support WWV/WWVB any more. The other problem=20=
is=20
these signals are only available here in the States. Since half of my sale=
s=20
are overseas a lot of people will not be able to use this feature.=20
May I ask that you reconsider the situation,=20
please? You seem to have overlooked the fact that the inexpensive WWVB type=20
modules are available for not only the USA, much of=20
Canada and central America, but also=20=
for=20
Europe and Japan. Since the compu=
ter=20
modules give a fully decoded time signal, it should be easy to make y=
our=20
board timing automatically fail safe for power outages and for automatic sta=
rt=20
up. The power requirements ARE designed for battery operation.
Your WWV tone decoder timing is only widely=20
available on one frequency during the day and on another during the nig=
ht=20
and only in North America / eastern Pacific. It is not a 'fit and forget' 24=
=20
hour timing solution, unlike many WWVB type systems.
Commercial seismic software DOES often use V=
LF=20
radio signals as alternatives to GPS and on-line timing.
>> And with most of the PSN st=
ation=20
having a full time Internet connection nowadays they always have the option=20=
to=20
use NTP etc as a time reference.
Not everyone CAN obtain a permanent network=20
connection and from my experience, you DO NEED to have access to a time=
set=20
program which MODIFIES (disciplines) your computer clock rate. A permanent l=
ine=20
connection is an expense which your customers do not need to have. I cannot=20
obtain a second phone line, even if I wished to pay the extra $290 / year li=
ne=20
rental.
Regards,
Chris Chapman
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