Re: [time-nuts] uncertainty calculations
On 4/14/17 8:37 AM, jimlux wrote:
If one is counting an unknown 1pps source with a counter that runs at 10
MHz (e.g. the error in any one measurement is uniformly distributed over
1 ppm) and you collect 100 samples,
is the (1 sigma) measurement uncertainty 0.1ppm * sqrt(100)/sqrt(12)
(standard deviation of a uniform distribution is 1/sqrt(12) )
(assuming for the moment that both sources have no underlying
variability - we're talking about the measurement uncertainty)
Oops..
0.1 ppm * 1/sqrt(N) * 1/sqrt(12)
That is, the standard deviation goes down as sqrt(N)
My NTGS50AA is suddenly lacking the ability to communicate. It's been
working fine for months, but I was trying a few things with my Raspberry
Pi NTP server.
Had GPSD accessing the NTGS50AA through a ch340 USB to serial adapter.
Found out Lady Heather displays much less info when connecting through
GPSD, so I went back to LH connecting directly to NTGS50AA through ch340
adapter on windows 7. Curiously, it was surveying, not in position lock.
So, I did a hard reset. Never heard from it since :(
If it's unplugged, all the lights behave as they should when you power
it up again. "Locked" light eventually comes on. PPS still works. Just
no serial. Even tried Trimble Studio with auto detect settings, no
connect here either. I've tried a second ch340 USB to serial adapter,
same deal. Any suggestions?
Thanks
Ed
Have you tried different serial settings I wonder if the hard reset mucked things up. have a Nortel as well, never had a issue with a reset but try changing a few thing sup. It may need the unusual 19200,7,Odd and 1 stop bit setting.
If you try a terminal program do you at least see some garbage characters?
-=Bryan=-
From: time-nuts time-nuts-bounces@febo.com on behalf of Ed Armstrong eds_equipment@verizon.net
Sent: April 15, 2017 1:13 AM
To: Discussion of precise time and frequency measurement
Subject: [time-nuts] NTGS50AA No Serial
My NTGS50AA is suddenly lacking the ability to communicate. It's been
working fine for months, but I was trying a few things with my Raspberry
Pi NTP server.
Had GPSD accessing the NTGS50AA through a ch340 USB to serial adapter.
Found out Lady Heather displays much less info when connecting through
GPSD, so I went back to LH connecting directly to NTGS50AA through ch340
adapter on windows 7. Curiously, it was surveying, not in position lock.
So, I did a hard reset. Never heard from it since :(
If it's unplugged, all the lights behave as they should when you power
it up again. "Locked" light eventually comes on. PPS still works. Just
no serial. Even tried Trimble Studio with auto detect settings, no
connect here either. I've tried a second ch340 USB to serial adapter,
same deal. Any suggestions?
Thanks
Ed
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and follow the instructions there.
I had a stupid problem with mine when doing some tests and I had the
same symptoms and it took me several days of tests to realize the problem.
The original flat cable that goes to the auxiliary board with the panel
lights and the RS-232 connector has the pins reversed so if you connect
the pin one to pin one you still get some LEDs on but no comms. Connect
it as per the attached photo. If the list deletes the attachments,
please ask me to send it directly.
El 15/04/2017 a las 13:11, Bryan _ escribió:
Have you tried different serial settings I wonder if the hard reset mucked things up. have a Nortel as well, never had a issue with a reset but try changing a few thing sup. It may need the unusual 19200,7,Odd and 1 stop bit setting.
If you try a terminal program do you at least see some garbage characters?
-=Bryan=-
From: time-nuts time-nuts-bounces@febo.com on behalf of Ed Armstrong eds_equipment@verizon.net
Sent: April 15, 2017 1:13 AM
To: Discussion of precise time and frequency measurement
Subject: [time-nuts] NTGS50AA No Serial
My NTGS50AA is suddenly lacking the ability to communicate. It's been
working fine for months, but I was trying a few things with my Raspberry
Pi NTP server.
Had GPSD accessing the NTGS50AA through a ch340 USB to serial adapter.
Found out Lady Heather displays much less info when connecting through
GPSD, so I went back to LH connecting directly to NTGS50AA through ch340
adapter on windows 7. Curiously, it was surveying, not in position lock.
So, I did a hard reset. Never heard from it since :(
If it's unplugged, all the lights behave as they should when you power
it up again. "Locked" light eventually comes on. PPS still works. Just
no serial. Even tried Trimble Studio with auto detect settings, no
connect here either. I've tried a second ch340 USB to serial adapter,
same deal. Any suggestions?
Thanks
Ed
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
time-nuts Info Page - American Febo Enterpriseshttps://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
www.febo.com
time-nuts is a low volume, high SNR list for the discussion of precise time and frequency measurement and related topics. To see the collection of prior postings to ...
and follow the instructions there.
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 had a stupid problem with mine when doing some tests and I had the
same symptoms and it took me several days of tests to realize the problem.
The original flat cable that goes to the auxiliary board with the panel
lights and the RS-232 connector has the pins reversed so if you connect
the pin one to pin one you still get some LEDs on but no comms. Connect
it as per the attached photo. If the list deletes the attachments,
please ask me to send it directly.
El 15/04/2017 a las 13:11, Bryan _ escribió:
Have you tried different serial settings I wonder if the hard reset mucked things up. have a Nortel as well, never had a issue with a reset but try changing a few thing sup. It may need the unusual 19200,7,Odd and 1 stop bit setting.
If you try a terminal program do you at least see some garbage characters?
-=Bryan=-
From: time-nuts time-nuts-bounces@febo.com on behalf of Ed Armstrong eds_equipment@verizon.net
Sent: April 15, 2017 1:13 AM
To: Discussion of precise time and frequency measurement
Subject: [time-nuts] NTGS50AA No Serial
My NTGS50AA is suddenly lacking the ability to communicate. It's been
working fine for months, but I was trying a few things with my Raspberry
Pi NTP server.
Had GPSD accessing the NTGS50AA through a ch340 USB to serial adapter.
Found out Lady Heather displays much less info when connecting through
GPSD, so I went back to LH connecting directly to NTGS50AA through ch340
adapter on windows 7. Curiously, it was surveying, not in position lock.
So, I did a hard reset. Never heard from it since :(
If it's unplugged, all the lights behave as they should when you power
it up again. "Locked" light eventually comes on. PPS still works. Just
no serial. Even tried Trimble Studio with auto detect settings, no
connect here either. I've tried a second ch340 USB to serial adapter,
same deal. Any suggestions?
Thanks
Ed
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
time-nuts Info Page - American Febo Enterpriseshttps://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
www.febo.com
time-nuts is a low volume, high SNR list for the discussion of precise time and frequency measurement and related topics. To see the collection of prior postings to ...
and follow the instructions there.
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 believe that the problem is that the error in any one measurement is
not uniformly distributed in exactly that way. If you are trying to
count how many 10 MHz (100 ns interval) intervals occur between the 1
PPS edges in a period counter, you have to deal with the following?
-
You might have any possible phase relationship between the two
signals. If they are exactly related by a 10^7 ratio, it's possible
for the 1 PPS edges to exactly coincide with the 10 MHz edges.
Depending on the type of gating circuit, you will have jitter and
possibly metastability resolving whether which edge occured first. The
same thing happens on the end of the measured interval, but (depending
on how it's set up) the propagation delays and metastability and
jitter might be different. So you could get millions of sequential
counts which were 1 count low, followed by millions of counts which
were one count high, with no counts exactly at 10^7. -
To stay away from such problems, most precision counters add a small
amount of controlled jitter (phase modulation) to the clock. When
averaged over many measurements the effects of the two edges (gate and
clock) lining up exactly are greatly reduced, since you are sliding
one back and forth across the other with the modulation and the chance
of metastability is small (assuming the signal being measured doesn't
happen to match the phase modulation frequency). -
The metastability problem depends on how the edges are compared. Some
traditional flip-flops and latches can be thought of as analog gain
elements connected so that they tend to sit in state A or state B,
which involve analog voltages and currents. If you graph the energy in
the system, the energy is low in state A, rises to a peak halfway
between A and B, and falls to a low value at state B. If the
recognition of the timing edge occurs early enough the system remains
in state A. If the timing is later the system is pushed toward the
peak, but doesn't get over it and returns to state A. But if the
timing is at the perfect location the system is balanced at the
potential energy peak, and only random noise can push the system into
a final state A or B over a significant length of time.
Sorry if this is considered obvious or trivial.
--
Bill Byrom N5BB
----- Original message -----
From: jimlux jimlux@earthlink.net
To: Discussion of precise time and frequency measurement time-nuts@febo.com
Subject: Re: [time-nuts] uncertainty calculations
Date: Fri, 14 Apr 2017 08:49:07 -0700
On 4/14/17 8:37 AM, jimlux wrote:
If one is counting an unknown 1pps source with a counter that
runs at 10
MHz (e.g. the error in any one measurement is uniformly
distributed over
1 ppm) and you collect 100 samples,
is the (1 sigma) measurement uncertainty 0.1ppm * sqrt(100)/sqrt(12)
(standard deviation of a uniform distribution is 1/sqrt(12) )
(assuming for the moment that both sources have no underlying
variability - we're talking about the measurement uncertainty)
Oops..
0.1 ppm * 1/sqrt(N) * 1/sqrt(12)
That is, the standard deviation goes down as sqrt(N)
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.