Cheap jitter measurements
Time-nuts!
With care I can measure GPS jitter on a RasPi to a bit over 300 nano sec
resolution. That is the smallest increment of the RasPi 3B clock with
a 64-bit kernel. That is clearly not time-nuts accuracy.
What would you guys suggest as the cheapest way to see jitter down to
around 1 nano second?
I'm thinking maybe something like a rubidium standard (FE-5680A) and
a TICC-TAPR? But that would put me out around $400.
The picPET does not look accurate enough. Maybe a clever way to use it
for more accuracy? Is there a picPET like thing cheaper than the
TICC-TAPR?
Ideas?
RGDS
GARY
Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
gem@rellim.com Tel:+1 541 382 8588
Veritas liberabit vos. -- Quid est veritas?
"If you can’t measure it, you can’t improve it." - Lord Kelvin
On Tue, 3 Apr 2018 10:47:37 -0700
"Gary E. Miller" gem@rellim.com wrote:
What would you guys suggest as the cheapest way to see jitter down to
around 1 nano second?
Look at Nick Sayers GPSDO and his interpolator. You wont get any
cheaper than that. Next best thing is to use a TDC7200 like in
the TICC.
Of course, you will need a standard that is stable enough on the
time scales you are looking at. Which is for short taus (<100s)
a good OCXO and for 1s to 10ks an Rb, and beyond that a Cs beam
standard or hydrogen maser.
Attila Kinali
--
<JaberWorky> The bad part of Zurich is where the degenerates
throw DARK chocolate at you.
Find a nice used 5370/5371? :)
There is a 5371 on ebay for $250 at the moment.
On Tue, Apr 3, 2018 at 1:47 PM, Gary E. Miller gem@rellim.com wrote:
Time-nuts!
With care I can measure GPS jitter on a RasPi to a bit over 300 nano sec
resolution. That is the smallest increment of the RasPi 3B clock with
a 64-bit kernel. That is clearly not time-nuts accuracy.
What would you guys suggest as the cheapest way to see jitter down to
around 1 nano second?
I'm thinking maybe something like a rubidium standard (FE-5680A) and
a TICC-TAPR? But that would put me out around $400.
The picPET does not look accurate enough. Maybe a clever way to use it
for more accuracy? Is there a picPET like thing cheaper than the
TICC-TAPR?
Ideas?
RGDS
GARY
Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
gem@rellim.com Tel:+1 541 382 8588
Veritas liberabit vos. -- Quid est veritas?
"If you can’t measure it, you can’t improve it." - Lord Kelvin
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.
Hi Gary,
One solution is to look for used hp, Fluke, or Racal time interval counters on eBay. 1 or 2 ns is pretty easy to find with a $100 or $200 budget. Look for Racal 1992 or hp 5334B as examples. If you plan to collect lots of data, you'll want GPIB (or RS232 / USB) connections to a PC and that will add to your net cost.
Another solution is to homebrew your own 1 ns counter. The downside is you will spend a month working out the bugs before you trust the data. Plus if you don't already have another counter to compare it against it makes development even harder.
Third solution is the TICC from TAPR. It's new and works out of the box. Lots of us use them. John did a very good job with the design. Highly recommended. It's a dual-channel time stamping counter so you can collect 1PPS data on two separate GPS receivers at the same time if you want. In that respect it's 2x as useful as a commercial time interval counter.
You mention jitter, not ADEV. I don't think you need a fancy timebase if all you want to measure is jitter. You can get a good feel for the jitter of a GPS / 1PPS output within a few samples. Even a minute of data is usually enough to establish the rms jitter value. If you want a full ADEV plot, then yes, you'd probably want at least an Rb for your reference.
See paragraph "Timing Stability" at http://leapsecond.com/pages/MG1613S/ for an example of what jitter from a GPS receiver looks like; in this case it's primarily sawtooth.
Right, the picPET has 400 ns resolution and so it is not the right tool for your nanosecond needs. I do have a 10 ns version that I use, but that's still a bit coarse for GPS work.
I have spare FEI Rb here; I'll send it if you want it. That way you can afford a TICC.
/tvb
----- Original Message -----
From: "Gary E. Miller" gem@rellim.com
To: "time-nuts" time-nuts@febo.com
Sent: Tuesday, April 03, 2018 10:47 AM
Subject: [time-nuts] Cheap jitter measurements
Time-nuts!
With care I can measure GPS jitter on a RasPi to a bit over 300 nano sec
resolution. That is the smallest increment of the RasPi 3B clock with
a 64-bit kernel. That is clearly not time-nuts accuracy.
What would you guys suggest as the cheapest way to see jitter down to
around 1 nano second?
I'm thinking maybe something like a rubidium standard (FE-5680A) and
a TICC-TAPR? But that would put me out around $400.
The picPET does not look accurate enough. Maybe a clever way to use it
for more accuracy? Is there a picPET like thing cheaper than the
TICC-TAPR?
Ideas?
RGDS
GARY
Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
gem@rellim.com Tel:+1 541 382 8588
Veritas liberabit vos. -- Quid est veritas?
"If you can’t measure it, you can’t improve it." - Lord Kelvin
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.
Gary
There is a Blast from the past the PIC TIC. Richard McCorkle did it and in its time was widely popular. He helped me on many projects so I included his boards with my board orders. Not being a time nut I never took a closer look at his board. Having recently revisited the subject for simple low cost monitoring of sources versus GPS and looking at Riley's comments found out that Richard used schematic capture, not what you want to use in timing applications. Did do a new board with ground plane. Also did a V drive with time chip for long term data recording using a USB stick. The unit is well documented.
I have boards and you are welcomed to a set, can also help with key chips, only one SMD, we plan to build and test but lately have been distracted with a minor redo of the excellent Riley Dual Mixer and my 2 channel Ping Pong counter that Corby loves so much that he has three. Had some interface problems that had us going for weeks. When you chase 1 E-13 and 14 nothing comes easy.
Again if interested contact me off list.
Bert Kehren
In a message dated 4/3/2018 2:35:18 PM Eastern Standard Time, gem@rellim.com writes:
Time-nuts!
With care I can measure GPS jitter on a RasPi to a bit over 300 nano sec
resolution. That is the smallest increment of the RasPi 3B clock with
a 64-bit kernel. That is clearly not time-nuts accuracy.
What would you guys suggest as the cheapest way to see jitter down to
around 1 nano second?
I'm thinking maybe something like a rubidium standard (FE-5680A) and
a TICC-TAPR? But that would put me out around $400.
The picPET does not look accurate enough. Maybe a clever way to use it
for more accuracy? Is there a picPET like thing cheaper than the
TICC-TAPR?
Ideas?
RGDS
GARY
Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
gem@rellim.com Tel:+1 541 382 8588
Veritas liberabit vos. -- Quid est veritas?
"If you can’t measure it, you can’t improve it." - Lord Kelvin
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.
Hi
I would add the HP 5335 to the list of counters to look for. The surplus market can be really
weird. A 5334 should be less than a 5335, but on any given day, that may not be true. The
5370 and 5345 are also worth looking for. Target price (at least for me) wold be < $150 for a
quick buy and < $70 if I was willing to shop for a while.
Getting data out of the older counters will involve GPIB. If you are not already set up to do
that, there will be the cost of a cable and a simple adapter.
If you want to move up a generation, the 53131 and 53132 are higher resolution devices than
the 5334 and 5335. They give you the benefit of a serial port. No GPIB stuff to bother with.
Finding one at price lower than the TAPR counter …. probably not.
Bob
On Apr 3, 2018, at 3:04 PM, Tom Van Baak tvb@leapsecond.com wrote:
Hi Gary,
One solution is to look for used hp, Fluke, or Racal time interval counters on eBay. 1 or 2 ns is pretty easy to find with a $100 or $200 budget. Look for Racal 1992 or hp 5334B as examples. If you plan to collect lots of data, you'll want GPIB (or RS232 / USB) connections to a PC and that will add to your net cost.
Another solution is to homebrew your own 1 ns counter. The downside is you will spend a month working out the bugs before you trust the data. Plus if you don't already have another counter to compare it against it makes development even harder.
Third solution is the TICC from TAPR. It's new and works out of the box. Lots of us use them. John did a very good job with the design. Highly recommended. It's a dual-channel time stamping counter so you can collect 1PPS data on two separate GPS receivers at the same time if you want. In that respect it's 2x as useful as a commercial time interval counter.
You mention jitter, not ADEV. I don't think you need a fancy timebase if all you want to measure is jitter. You can get a good feel for the jitter of a GPS / 1PPS output within a few samples. Even a minute of data is usually enough to establish the rms jitter value. If you want a full ADEV plot, then yes, you'd probably want at least an Rb for your reference.
See paragraph "Timing Stability" at http://leapsecond.com/pages/MG1613S/ for an example of what jitter from a GPS receiver looks like; in this case it's primarily sawtooth.
Right, the picPET has 400 ns resolution and so it is not the right tool for your nanosecond needs. I do have a 10 ns version that I use, but that's still a bit coarse for GPS work.
I have spare FEI Rb here; I'll send it if you want it. That way you can afford a TICC.
/tvb
----- Original Message -----
From: "Gary E. Miller" gem@rellim.com
To: "time-nuts" time-nuts@febo.com
Sent: Tuesday, April 03, 2018 10:47 AM
Subject: [time-nuts] Cheap jitter measurements
Time-nuts!
With care I can measure GPS jitter on a RasPi to a bit over 300 nano sec
resolution. That is the smallest increment of the RasPi 3B clock with
a 64-bit kernel. That is clearly not time-nuts accuracy.
What would you guys suggest as the cheapest way to see jitter down to
around 1 nano second?
I'm thinking maybe something like a rubidium standard (FE-5680A) and
a TICC-TAPR? But that would put me out around $400.
The picPET does not look accurate enough. Maybe a clever way to use it
for more accuracy? Is there a picPET like thing cheaper than the
TICC-TAPR?
Ideas?
RGDS
GARY
Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
gem@rellim.com Tel:+1 541 382 8588
Veritas liberabit vos. -- Quid est veritas?
"If you can’t measure it, you can’t improve it." - Lord Kelvin
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.
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 the practical side, the 5345 is HEAVY due to its older technology—doing
what it does with first-generation ICs required HP jam an enormous amount
of circuitry into a fairly small physical package.
Jeremy
N6WFO
On Tue, Apr 3, 2018 at 2:39 PM Bob kb8tq kb8tq@n1k.org wrote:
Hi
I would add the HP 5335 to the list of counters to look for. The surplus
market can be really
weird. A 5334 should be less than a 5335, but on any given day, that may
not be true. The
5370 and 5345 are also worth looking for. Target price (at least for me)
wold be < $150 for a
quick buy and < $70 if I was willing to shop for a while.
Getting data out of the older counters will involve GPIB. If you are not
already set up to do
that, there will be the cost of a cable and a simple adapter.
If you want to move up a generation, the 53131 and 53132 are higher
resolution devices than
the 5334 and 5335. They give you the benefit of a serial port. No GPIB
stuff to bother with.
Finding one at price lower than the TAPR counter …. probably not.
Bob
On Apr 3, 2018, at 3:04 PM, Tom Van Baak tvb@leapsecond.com wrote:
Hi Gary,
One solution is to look for used hp, Fluke, or Racal time interval
counters on eBay. 1 or 2 ns is pretty easy to find with a $100 or $200
budget. Look for Racal 1992 or hp 5334B as examples. If you plan to collect
lots of data, you'll want GPIB (or RS232 / USB) connections to a PC and
that will add to your net cost.
Another solution is to homebrew your own 1 ns counter. The downside is
you will spend a month working out the bugs before you trust the data. Plus
if you don't already have another counter to compare it against it makes
development even harder.
Third solution is the TICC from TAPR. It's new and works out of the box.
Lots of us use them. John did a very good job with the design. Highly
recommended. It's a dual-channel time stamping counter so you can collect
1PPS data on two separate GPS receivers at the same time if you want. In
that respect it's 2x as useful as a commercial time interval counter.
You mention jitter, not ADEV. I don't think you need a fancy timebase if
all you want to measure is jitter. You can get a good feel for the jitter
of a GPS / 1PPS output within a few samples. Even a minute of data is
usually enough to establish the rms jitter value. If you want a full ADEV
plot, then yes, you'd probably want at least an Rb for your reference.
See paragraph "Timing Stability" at http://leapsecond.com/pages/MG1613S/
for an example of what jitter from a GPS receiver looks like; in this case
it's primarily sawtooth.
Right, the picPET has 400 ns resolution and so it is not the right tool
for your nanosecond needs. I do have a 10 ns version that I use, but that's
still a bit coarse for GPS work.
I have spare FEI Rb here; I'll send it if you want it. That way you can
afford a TICC.
/tvb
----- Original Message -----
From: "Gary E. Miller" gem@rellim.com
To: "time-nuts" time-nuts@febo.com
Sent: Tuesday, April 03, 2018 10:47 AM
Subject: [time-nuts] Cheap jitter measurements
Time-nuts!
With care I can measure GPS jitter on a RasPi to a bit over 300 nano sec
resolution. That is the smallest increment of the RasPi 3B clock with
a 64-bit kernel. That is clearly not time-nuts accuracy.
What would you guys suggest as the cheapest way to see jitter down to
around 1 nano second?
I'm thinking maybe something like a rubidium standard (FE-5680A) and
a TICC-TAPR? But that would put me out around $400.
The picPET does not look accurate enough. Maybe a clever way to use it
for more accuracy? Is there a picPET like thing cheaper than the
TICC-TAPR?
Ideas?
RGDS
GARY
Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
gem@rellim.com Tel:+1 541 382 8588
Veritas liberabit vos. -- Quid est veritas?
"If you can’t measure it, you can’t improve it." - Lord Kelvin
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to
and follow the instructions there.
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go 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.
--
Sent from my iPad 4.
I would say my implementation is simpler than Nick’s:
https://www.eevblog.com/forum/projects/lars-diy-gpsdo-with-arduino-and-1ns-resolution-tic/?all . It is just an Arduino+ two HCMOS and a few passive components.
From the beginning Nick copied my interpolator. Later he added a FET that might act as a constant current generator but I doubt it works very well. At least the variance of the FET’s are to large. The temperature stability is not that good either. So far I have not seen any tests of this. The Elektor GPS by Joost Breed copied Nick’s interpolator and a graph from that shows large non-linearities as I can see.
My simple interpolator that I linearize in software is not perfect but able to get down to about 1ns linearity by setting min-max and a square term. By using Tom Van Baak’s PICDIV 26 it is fairly easy to set the linearity. Information is in the instruction found on EEVblog. In the last pages I also enclosed ADEV, TDEV and a frequency plot direct from Timelab that works very well with the controller. ADEV at 1s is 8E-10.
Also I don’t think Nick sends out the ns direct (absolutely not linearized) on the serial port as I do. As I said before this works very well with timelab.
After a lot of testing I also thinks both my hardware and software is robust.
Otherwise I would recommend the TAPR-TICC that I nowadays use more than my 5370. Good resolution and much lower power dissipation.
Lars
From: Attila Kinalimailto:attila@kinali.ch
Sent: den 3 april 2018 21:04
On Tue, 3 Apr 2018 10:47:37 -0700
"Gary E. Miller" gem@rellim.com wrote:
What would you guys suggest as the cheapest way to see jitter down to
around 1 nano second?
Look at Nick Sayers GPSDO and his interpolator. You wont get any
cheaper than that. Next best thing is to use a TDC7200 like in
the TICC.
Of course, you will need a standard that is stable enough on the
time scales you are looking at. Which is for short taus (<100s)
a good OCXO and for 1s to 10ks an Rb, and beyond that a Cs beam
standard or hydrogen maser.
Attila Kinali
--
<JaberWorky> The bad part of Zurich is where the degenerates
throw DARK chocolate at you.
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.
Time Nuts!
TL:DR: I decided to go with the Rb and TAPR-TICC.
Long story:
Thank you to all that made such good suggestions. I think you pretty
much covered the spectrum of options to measuring PPS very nicely.
I'm tempted by the used 5370/5371 idea. It has 150 ps resolution and
does a ton of fun things. But they are large, power hungry (500W), and
only talk over GPIB. I just want a TICC and the rest is overhead. All
the cool charts, graphs and histograms on the CRT do me no good.
Boxes like the Racal 1992 and hp 5334b are more interesting. Most
1991 on ebay are for parts only, and there are more web pages on how
to repair them than how to use them. They only resolve down to 1 nano
second. I do not see any of either on ebay with rs-232.
Since I'm just working with 5V and 3.3V logic levels, I don't need a
fancy front end, and output of logic level and/or USB serial is also
nice for using on a RasPi.
So I looked at the various hobbyist solutions. There are some
'interpolator' designs, but I'd need to build them myself and they also
only get to around 1 nano second. Some maybe a lot better performance,
but more than some assembly required. Also I would have to figure out
how to measure my measuring tool to see what I got.
So, I'm back to the Rb and TAPR-TICC solution. No one will seriously
question the Rb accuracy, at least when compared to GPS. The TAPR-TICC
comes fully assembled, tested and specified. Easy USB serial interface.
Just a tad more expensive than other solutions. 60 picosecond
resolution and less than 100 picosecond typical jitter. ADev below
1x10-10. All way better than I need, so few should argue with using it
to measure GPS PPS.
A few downsides. I'll have to write my own code for pretty graphs, but
at least I can do it on UNIX. Not a total solution, I still need to
add a GPSDO and cable it all together.
Now I just have to wait for the postman.
Once again, thanks for all the suggestions.
RGDS
GARY
Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
gem@rellim.com Tel:+1 541 382 8588
Veritas liberabit vos. -- Quid est veritas?
"If you can’t measure it, you can’t improve it." - Lord Kelvin