Re: [time-nuts] Precision DACs

[Scott Stobbe]

As a clarification, the AD5791 is the minimum implementation of a DAC, it's
merely a resistor array with SPI controllable switches. (But an impressive
set of resistors, no doubt. Maybe with a dash of secret sauce in digital
calibration). The only guaranteed specs for the AD5791 are at DC,
everything else is up to the designer.

The thermal noise of the AD5791 is 4.07 nV/rtHz * sqrt( 3.4 ) = 7.5 nV/rtHz
(same as spec'd), where 3.4 is the nominal output resistance in kOhms.
Flicker noise is due to the voltage reference, reference buffers, and post
DAC buffer.

The settling time after code transition is complete, is based of the load
capacitance as seen by the DAC, and the buffer amplifier's transient
response. The settling time of a pole to +- 0.5 ppm is 15 time constants.

Even the sample application circuit only achieved a THD of 97 dB for a 1
kHz tone, which is equivalent to 16 bits.

The INL/DNL are measured at DC, if you were to measure the INL/DNL at 1Msps
on a half bit code across span (dither 1 LSB), the results would be
dramatically different due to glitching on code transition. That being
said, they are kept separate not to confuse sources of error.

20 effective bits is 122 dB signal to every thing else.

On Mon, Jul 25, 2016 at 7:40 PM, Attila Kinali  wrote:

> On Sun, 24 Jul 2016 23:48:05 -0400
> Scott Stobbe  wrote:
>
> > I doubt the AD5791 does much better than 16 bits operating at 1 Msps,
> when
> > you include glitch energy, noise, and distortion.
>
> What makes you think so?
>
> Yes, if you are using the full 500kHz bandwidth then the rms noise voltage
> will be 5uV.. or 35uVp-p. But even just going down to a 1kHz bandwith
> gives 235nVrms/1.5uVp-p (plus 1/f noise of 1.1uVp-p). So we are within
> the 1ppm for any output larger than ~2V.
>
> The DNL and INL are low enough that I don't think they cause any more
> trouble then you'd expect from a DAC normally.
>
> I don't know how to make use of the glitch specs and turn them
> precision values.
>
> Attila Kinali
>
> --
> Malek's Law:
> Any simple idea will be worded in the most complicated way.
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Re: [time-nuts] The home time-lab

[jimlux]

On 7/25/16 6:55 AM, Bob Camp wrote:

Hi

If you go back far enough in time …. there is another alternative:

   Big rectifier bank, turning AC into DC, often off of multiple phases or 
sources.

   Big DC motor running into a fairly large flywheel.

   AC generator (or in some cases DC generators) running off of the shaft

   A tuning fork (yes state of the art timing) based control on the AC 
output frequency

   A saturated reactor control loop on the generator side, same thing on 
the motor side.

Wonderfull stuff. State of the art UPS for your shipboard computer in 1962. Ear 
muffs anyone?

Bob


we had a system like this to turn 60 Hz into 50 Hz with a toothed belt 
drive between synchronous motor and synchronous generator.  It whined.. 
"Satan's Siren" is what we called it.


IBM mainframes used a similar scheme but I can't remember the details.


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Re: [time-nuts] controlling instruments using USB

[Pete Lancashire]

here is what the author has to say

https://joeyh.name/code/alien/

On Mon, Jul 25, 2016 at 7:33 PM, Pete Lancashire
 wrote:
> Never tried this Alien convert RPM to DEB
>
> https://www.howtoforge.com/converting_rpm_to_deb_with_alien
>
>
>
> On Mon, Jul 25, 2016 at 6:02 PM, jimlux  wrote:
>> Semi-off-topic..
>>
>> I've got a bunch of Keysight/Agilent/HP instruments with USB interfaces that
>> I want to control from Python.  On Mac and PC, the PyVisa library works
>> great (either the one with the NI back end or the python only back end )
>>
>> But, on Ubuntu, there's no way to install the NI drivers (RH install only,
>> and Ubuntu is debian..)
>>
>> So, I've been doing usbtmc, which sort of works.  (after figuring out all
>> the udev rules stuff)
>>
>> If I do something like this from the python interpreter:
>>
> import usbtmc
> myinst = usbtmc.Instrument( mfr, product)
> myinst.write('some command')
>>
>> it works fine.
>>
>> But if I put the same three linesin a .py file and run it, it doesn't always
>> work.. sometimes, you need to send the command twice.
>>
>> It seems it might be a timing thing (in libusb or usbtmc?) but putting some
>> sleep() in between connecting to the instrument and doing the write doesn't
>> seem to work all the time.
>>
>> Very curious.
>>
>> Any ideas?
>> ___
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Re: [time-nuts] controlling instruments using USB

[Thomas Valerio]

Have you looked at alien to convert the rpm to a deb?

   https://www.google.com/#q=alien+package+conversion


> Semi-off-topic..
>
> I've got a bunch of Keysight/Agilent/HP instruments with USB interfaces
> that I want to control from Python.  On Mac and PC, the PyVisa library
> works great (either the one with the NI back end or the python only back
> end )
>
> But, on Ubuntu, there's no way to install the NI drivers (RH install
> only, and Ubuntu is debian..)
>
> So, I've been doing usbtmc, which sort of works.  (after figuring out
> all the udev rules stuff)
>
> If I do something like this from the python interpreter:
>
>  >>> import usbtmc
>  >>> myinst = usbtmc.Instrument( mfr, product)
>  >>> myinst.write('some command')
>
> it works fine.
>
> But if I put the same three linesin a .py file and run it, it doesn't
> always work.. sometimes, you need to send the command twice.
>
> It seems it might be a timing thing (in libusb or usbtmc?) but putting
> some sleep() in between connecting to the instrument and doing the write
> doesn't seem to work all the time.
>
> Very curious.
>
> Any ideas?
> ___
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Re: [time-nuts] controlling instruments using USB

[Pete Lancashire]

Never tried this Alien convert RPM to DEB

https://www.howtoforge.com/converting_rpm_to_deb_with_alien



On Mon, Jul 25, 2016 at 6:02 PM, jimlux  wrote:
> Semi-off-topic..
>
> I've got a bunch of Keysight/Agilent/HP instruments with USB interfaces that
> I want to control from Python.  On Mac and PC, the PyVisa library works
> great (either the one with the NI back end or the python only back end )
>
> But, on Ubuntu, there's no way to install the NI drivers (RH install only,
> and Ubuntu is debian..)
>
> So, I've been doing usbtmc, which sort of works.  (after figuring out all
> the udev rules stuff)
>
> If I do something like this from the python interpreter:
>
 import usbtmc
 myinst = usbtmc.Instrument( mfr, product)
 myinst.write('some command')
>
> it works fine.
>
> But if I put the same three linesin a .py file and run it, it doesn't always
> work.. sometimes, you need to send the command twice.
>
> It seems it might be a timing thing (in libusb or usbtmc?) but putting some
> sleep() in between connecting to the instrument and doing the write doesn't
> seem to work all the time.
>
> Very curious.
>
> Any ideas?
> ___
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[time-nuts] GPS receiver time message offsets to 1PPS

[Mark Sims]

Heather will take either time format,  but requests the receiver to send T2 
format.

I originally thought the SCPI receivers would be right on time due to my 
original measurements of their message jitter,  but when I started measureing 
the actual message arrival times... surprise, surprise, surprise!I think 
the issue is due to the fact that they use Motorola receivers and those ramp 
the time the message comes out (1 msec per second).

The other surprise was the Jupiter-T message is 1.2 seconds after the 1PPS... 
that's just plain wrong... it reports the correct leap-second offset, but maybe 
they are off by a second internally?  Maybe premature application of the leap 
pending?  Maybe it's always just plain wrong?

Attached is a plot of the evil Z3801A in action...   


Those ramps don't make sense to me.  Mine are consistently right on.
Are you using T1 or T2 format?  t1 is the default.  I'm using T2.  (Seems 
unlikely it would make a difference, but stranger things have happened.)

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Re: [time-nuts] GPS receiver time message offsets to 1PPS

[Hal Murray]

hol...@hotmail.com said:
> Here are the results of measuring the difference between the time code in a
> GPS receiver time message and the arrival time of the last byte of the
> message.  Negative values mean that the receiver sends the timing message
> after the 1PPS pulse that it describes. The table also shows the standard
> deviation of the message arrival times. 

Neat.  Thanks.

hol...@hotmail.com said:
(slight snippage to avoid line wraps)
> Z3812A ...  1450.5  0.6  (ramps 950 .. 1950 over 1000 secs)
> Z3801A ...   1341.5  2.0  (ramps 941 .. 1841 over 1000 secs) 

Those ramps don't make sense to me.  Mine are consistently right on.

Are you using T1 or T2 format?  t1 is the default.  I'm using T2.  (Seems 
unlikely it would make a difference, but stranger things have happened.)




-- 
These are my opinions.  I hate spam.



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[time-nuts] controlling instruments using USB

[jimlux]

Semi-off-topic..

I've got a bunch of Keysight/Agilent/HP instruments with USB interfaces 
that I want to control from Python.  On Mac and PC, the PyVisa library 
works great (either the one with the NI back end or the python only back 
end )


But, on Ubuntu, there's no way to install the NI drivers (RH install 
only, and Ubuntu is debian..)


So, I've been doing usbtmc, which sort of works.  (after figuring out 
all the udev rules stuff)


If I do something like this from the python interpreter:

>>> import usbtmc
>>> myinst = usbtmc.Instrument( mfr, product)
>>> myinst.write('some command')

it works fine.

But if I put the same three linesin a .py file and run it, it doesn't 
always work.. sometimes, you need to send the command twice.


It seems it might be a timing thing (in libusb or usbtmc?) but putting 
some sleep() in between connecting to the instrument and doing the write 
doesn't seem to work all the time.


Very curious.

Any ideas?
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Re: [time-nuts] The home time-lab

[Attila Kinali]

On Mon, 25 Jul 2016 12:28:52 -0500
David  wrote:

> I have never seen one which did not use a class-D output with L-C
> filtering.  Total efficiency is in the 84 to 92 percent range.

Actually, the better ones have 3 level or 5 level inverters (or even more).
Ie their output stages can not only produce +340V and -340V, but
also 0V (for the 3 level) and +/-170V (for the 5 level). For obvious
reasons, this gives a nicer output waveform that needs less filtering.
While the 3 level is easy to build, the 5 levels and more require
a flying capacitor (or multiple for more than 5 levels). The handling of
this capacitor is kind of tricky as you need to ensure that the flying
capacitor has the right voltage under all conditions. For those interested,
quite a few papers on that topic are publicly available. Please excuse me
not linking to any of these, but I know very little of inverters, so I do
not know which one of the papers would be the right ones to read.

Attila Kinali

-- 
Malek's Law:
Any simple idea will be worded in the most complicated way.
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Re: [time-nuts] GPS receiver time message offsets to 1PPS

[Gary E. Miller]

Yo Mark!

On Mon, 25 Jul 2016 22:51:01 +
Mark Sims  wrote:

> Here are the results of measuring the difference between the time
> code in a GPS receiver time message and the arrival time of the last
> byte of the message.  Negative values mean that the receiver sends
> the timing message after the 1PPS pulse that it describes. The table
> also shows the standard deviation of the message arrival times.

Nicely done!  Real data!

RGDS
GARY
---
Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
g...@rellim.com  Tel:+1 541 382 8588


pgp6w6sGH3pz0.pgp
Description: OpenPGP digital signature
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Re: [time-nuts] Precision DACs

[Attila Kinali]

On Sun, 24 Jul 2016 23:48:05 -0400
Scott Stobbe  wrote:

> I doubt the AD5791 does much better than 16 bits operating at 1 Msps, when
> you include glitch energy, noise, and distortion.

What makes you think so?

Yes, if you are using the full 500kHz bandwidth then the rms noise voltage
will be 5uV.. or 35uVp-p. But even just going down to a 1kHz bandwith
gives 235nVrms/1.5uVp-p (plus 1/f noise of 1.1uVp-p). So we are within
the 1ppm for any output larger than ~2V.

The DNL and INL are low enough that I don't think they cause any more
trouble then you'd expect from a DAC normally.

I don't know how to make use of the glitch specs and turn them
precision values.

Attila Kinali

-- 
Malek's Law:
Any simple idea will be worded in the most complicated way.
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Re: [time-nuts] Precision DACs

[Attila Kinali]

On Sun, 24 Jul 2016 19:17:29 -0500
David  wrote:

> There *has* to be a better way to do this.  Maybe we could build a
> wooden badger ...

What? Has the wooden rabbit failed?

As I said, I looked into this some time ago and I couldn't come up
with any "easy" way to build a DAC with more than 20 (real) bits that
has a sampling rate higher than a couple of Hz. Even what the audio
people do, if they do not use of the shelf snake-oil DACs is pretty
hard core tech (and smells even more like snake oil)... nothing you'd
do ony your kitchen table. Somehow building your own atomic frequency
standard looked easier than doing your own high precision DAC.

If anyone has a good idea how to build a DAC with more than 20bit
that is somewhat DC stable (better than ~1ppm within an hour should
be enough), i'd like to hear about that.


Attila Kinali
-- 
Malek's Law:
Any simple idea will be worded in the most complicated way.
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[time-nuts] GPS receiver time message offsets to 1PPS

[Mark Sims]

Here are the results of measuring the difference between the time code in a GPS 
receiver time message and the arrival time of the last byte of the message.  
Negative values mean that the receiver sends the timing message after the 1PPS 
pulse that it describes. The table also shows the standard deviation of the 
message arrival times.


The test configuration was a Compaq N610C laptop (2 GHz Pentium, hardware 
serial port) running Linux Ubuntu Mate 15.10).  The time of the messagearrival 
was from the system clock synced to NTP.  The receivers were tested in native 
binary protocol and, if supported, NMEA.  The com port was runningat the 
default value for the receiver.  If not specified that was 9600:8:N:1Data was 
collected after the receiver had been tracking satellites for at least 1 hour 
and averaged over 4 hours.  The timings were also checked andagree with those 
on a 1.2 GHz Raspberry PI 3 and a quad-core 3 GHz box.


Although measuring the arrival time of the first byte of the timing 
messagemakes more technical sense (less variation due to timing message length) 
thesemeasurements are of the last byte of the message.  This was chosen to 
assistpeople trying to sync a clock to a GPS receiver without relying on the 
1PPSpulse.  They are also useful to people that want to know how long they 
haveto process a timing message (like to set a sawtooth compensation delay 
line) before the next 1PPS pulse comes out.


Several receivers appear to not sync their timing message to some 
referenceclock.  This causes the timing message arrival time to follow a ramp 
curve.


DeviceProtocol   Firmware   (msg-arrival)sdev

  (msecs)
=  =     =
Thunderbolt TSIP App:3.0 GPS:10.2 -52.9  6.2   (gold box)
Thunderbolt TSIP App:2.22 GPS:10.2-67.2 10.2   (red box)
Resolution-TTSIP GPS:1.26-140.0  5.4
Res-T SMT   TSIP GPS 2.7 -475.0 63.7
Starloc II  TSIP App:1.10 GPS:1.2-267.5  7.2
Trimble NTWx?   TSIP GPS 10.4 -44.9  1.2 
Nortel NTPx TSIP GPS 10.1 -61.8  1.4
Nortel NTGx TSIP GPS 10.5 -57.2  2.4


Ublox LEA-6Tbinary6.02 (36023)   -242.7  4.4
Ublox LEA-6TNMEA  6.02 (36023)   -198.7 11.1
Ublox Neo6M binary7.03 (45969)   -211.6  9.3
Ublox Neo6M NMEA  7.03 (45969)   -149.0  8.4
Ublox 7 binary1.00 (59842)   -186.9  2.6
Ublox 7 NMEA  1.00 (59842)   -152.9  7.9
Ublox NEO-8Mbinary2.01 (75350)   -192.7  9.1
Ublox NEO-8MNMEA  2.01 (75250)   -182.4  8.0

V.KEL SIRFIII   binaryGSW3.2.5   -432.8  6.1
V.KEL SIRFIII   NMEA  GSW3.2.5   -427.6  5.0

Navspark Mini   Venus81.7.27 15.8.18 -139.3  7.1

Adafruit Ultimate  NMEA  -428.2 39.8

Skylab SKM53NMEA -492.0 37.8  (has short 
jumps to usually -180)

Jupiter-T   Zodiac93.07 -1263.6  3.3
Juptier-T   Motorola  93.07  -774.5  4.7  (ramps -274 
.. -1274 over 1000 secs)
Jupiter PicoZodiac14.00 11/28/05-1236.9  0.4  (ramps -1225 
.. -1245 over 130 minutes)
Jupiter PicoMotorola  14.00 11/28/05 -771.0  4.7  (ramps -1271 
.. -271 over 1000 secs)

Motorola UT+Motorola  R5122U1112  250.5  5.0  (ramps -250 
.. +750 over 900 seconds)
Synergy M12+Motorola  P273T12T11  300.5  1.1  (ramps -200 
.. +800 over 1000 seconds)

Z3812A  SCPI  X98-4-A1450.5  0.6  (ramps 950 .. 
1950 over 1000 secs)
Z3801A  SCPI 19.2K3543A  1341.5  2.0  (ramps 941 .. 
1841 over 1000 secs)
Symmetricom UCCM-P 57.6K  1.0.0.2-01 -115.5  3.6  (ramps -109 
.. -119 over 10 seconds)
Trimble UCCM 57.6K3.0.0.11-0 -278.5  3.1
 

  
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[time-nuts] [LEAPSECS] Leap second to be introduced at midnight UTC December 31 this year

[Mark Sims]

And somebody paid well over 10 times the market rate to lease server space that 
was one building closer to the NYSE computers.  My idea to put an end to this 
bogo-trading nonsense is to add a random delay to all the trades.   



> Someone recently built a new fiber route from Chicago to NY because it was 
> just a touch shorter. The distances are down to hundredths of a ms.   
>
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Re: [time-nuts] [LEAPSECS] Leap second to be introduced at midnight UTC December 31 this year

[Michael Wouters]

I'd be interested to know how 10ns less latency is useful. AFAIK, a high
speed trading system consists of multiple processing nodes, which certainly
could have a 10ns accurate time reference eg via PTP, but latency and
jitter would limit time stamping of transactions to the microsecond level.
Unless of course, the critical bits are all running on dedicated hardware.

Cheers
Michael

On Tuesday, 26 July 2016, bownes  wrote:

>
> A second here or there is a very big deal to those of us in the financial
> and database worlds.
>
> Aside from the well known instances involving electronic trading I have
> customers fighting over cabinet positions and cable lengths to place
> processors closer to disk drives and on switch paths with 10ns less latency.
>
>
>
>
>
> > On Jul 25, 2016, at 16:57, Mark Sims >
> wrote:
> >
> > Apple's new file system timestamps files with nanosecond resolution.   A
> lot of Linux file systems also do that now.   The nanosecond ain't what it
> used to be...  I can imagine people wanting picosecond timestamps in the
> near future.  Who knows,  maybe we'll have something like NTP compensating
> for light-speed delay for the gap between the read/write heads and disk
> surface (assuming we still use heads and surfaces)  ; -)
> > 
> > Except that you still have the issue of “what time did this file get
> changed”. To most of us, that’s not really a big deal. A second either way
> … who cares.
> > ___
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Re: [time-nuts] [LEAPSECS] Leap second to be introduced at midnight UTC December 31 this year

[bownes]

We've been dealing with speed of light issues for over 20 years in the 
financial world. And telecom. 

Someone recently built a new fiber route from Chicago to NY because it was just 
a touch shorter. The distances are down to hundredths of a ms. 

> On Jul 25, 2016, at 17:41, Bob Camp  wrote:
> 
> Hi
> 
> In these days of computers trading with computers, the whole issue of “who 
> did what when” can 
> result in major money trading hands. I’m sure that at some point the 
> financial markets will have to
> deal with light speed issues and geography if they have not already.  
> 
> Bob
> 
>> On Jul 25, 2016, at 4:57 PM, Mark Sims  wrote:
>> 
>> Apple's new file system timestamps files with nanosecond resolution.   A lot 
>> of Linux file systems also do that now.   The nanosecond ain't what it used 
>> to be...  I can imagine people wanting picosecond timestamps in the near 
>> future.  Who knows,  maybe we'll have something like NTP compensating for 
>> light-speed delay for the gap between the read/write heads and disk surface 
>> (assuming we still use heads and surfaces)  ; -)
>> 
>> Except that you still have the issue of “what time did this file get 
>> changed”. To most of us, that’s not really a big deal. A second either way … 
>> who cares. 
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Re: [time-nuts] The home time-lab

[Charles Steinmetz]

Brooke wrote:


But a relay switched UPS, like mine, does nothing to the line waveform,
so the Sola offers a lot of improvement.

Since the Sola does not help getting a sine waveform, it may be better
to put it on the input since that might make dropout detection more
reliable?


Instead of continuing to fiddle around with two sort-of partial 
solutions that do not actually solve the problems, why not just buy one 
or more proper online UPS boxes?  Several of us have mentioned specific 
part numbers, where you can look for them at decent prices, and how to 
maintain and care for them.


This alternative would solve decisively the problems you (and Bob) are 
seeking to solve, and the cost is not extravagant (it would be even more 
economical if you hadn't already bought the offline UPS and the CVT -- 
perhaps you can sell them to recover some of the cost).


It is details like these that distinguish a "home time lab" from "a 
bunch of test equipment in the basement."


Best regards,

Charles


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Re: [time-nuts] [LEAPSECS] Leap second to be introduced at midnight UTC December 31 this year

[bownes]

A second here or there is a very big deal to those of us in the financial and 
database worlds. 

Aside from the well known instances involving electronic trading I have 
customers fighting over cabinet positions and cable lengths to place processors 
closer to disk drives and on switch paths with 10ns less latency. 





> On Jul 25, 2016, at 16:57, Mark Sims  wrote:
> 
> Apple's new file system timestamps files with nanosecond resolution.   A lot 
> of Linux file systems also do that now.   The nanosecond ain't what it used 
> to be...  I can imagine people wanting picosecond timestamps in the near 
> future.  Who knows,  maybe we'll have something like NTP compensating for 
> light-speed delay for the gap between the read/write heads and disk surface 
> (assuming we still use heads and surfaces)  ; -)
> 
> Except that you still have the issue of “what time did this file get 
> changed”. To most of us, that’s not really a big deal. A second either way … 
> who cares.   
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Re: [time-nuts] [LEAPSECS] Leap second to be introduced at midnight UTC December 31 this year

[Bob Camp]

Hi

In these days of computers trading with computers, the whole issue of “who did 
what when” can 
result in major money trading hands. I’m sure that at some point the financial 
markets will have to
deal with light speed issues and geography if they have not already.  

Bob

> On Jul 25, 2016, at 4:57 PM, Mark Sims  wrote:
> 
> Apple's new file system timestamps files with nanosecond resolution.   A lot 
> of Linux file systems also do that now.   The nanosecond ain't what it used 
> to be...  I can imagine people wanting picosecond timestamps in the near 
> future.  Who knows,  maybe we'll have something like NTP compensating for 
> light-speed delay for the gap between the read/write heads and disk surface 
> (assuming we still use heads and surfaces)  ; -)
> 
> Except that you still have the issue of “what time did this file get 
> changed”. To most of us, that’s not really a big deal. A second either way … 
> who cares.
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Re: [time-nuts] Symmetricom Power On Counter

[Bob Camp]

Hi

Maybe it only has a 20 year life if you power it up 50% of the time :)
Somehow I doubt that it only has a 10 year “power on” life. 

Bob

> On Jul 25, 2016, at 3:55 PM, Skip Withrow  wrote:
> 
> Hello Time-Nuts,
> 
> I just ran a Symmetricom X72 for 10 days to check the rate of the Pwr HRS
> counter.  At one point I thought I did this with an SA.22c and found a
> discrepancy between actual number of hours run and the counter increment.
> I can report that the X72 does appear to count hours correctly.  After
> running for 233 hours the hex counter incremented by 233 decimal.
> 
> This leaves me with some questions though.  The counter in the unit is four
> hex digits giving a max count of 2^16 or about 65,000.  The life of the X72
> is supposed to be about 20 years (roughly 180,000 hours).  So what happens
> to the unit on overflow, does the counter just rollover?  So how do you
> tell a new unit from one with 70,000 hours on it?  And there is also a
> service bit that is supposed to switch when there are several months of
> life left, what drives this bit?  Is it some kind of lamp life measurement
> (like the LPRO), and is the power on counter involved in any way?
> 
> The Symmetricom X72 and SA.22c seem to be cousins, I have not played with
> an X99 and don't know if it is related.  If someone has insight into these
> units I would be most interested in knowing some of the answers.  In fact,
> the 'w' command dumps about 26 different values (all in hex) and having the
> secret decoder ring for what the item mnemonics are and the scaling of the
> displayed values  would be very useful.  The user manual lists the 'w'
> command but gives no information regarding the resulting display that I can
> find.
> 
> Thanks in advance for any help.
> 
> Regards,
> Skip Withrow
> 303-790-1830
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[time-nuts] [LEAPSECS] Leap second to be introduced at midnight UTC December 31 this year

[Mark Sims]

Apple's new file system timestamps files with nanosecond resolution.   A lot of 
Linux file systems also do that now.   The nanosecond ain't what it used to 
be...  I can imagine people wanting picosecond timestamps in the near future.  
Who knows,  maybe we'll have something like NTP compensating for light-speed 
delay for the gap between the read/write heads and disk surface (assuming we 
still use heads and surfaces)  ; -)

Except that you still have the issue of “what time did this file get changed”. 
To most of us, that’s not really a big deal. A second either way … who cares.   
   
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[time-nuts] Venus838LPx-T opinions?

[Mark Sims]

 I have a Z3812A that I added back in the GPS receiver and modified it (moving 
6 zero ohm resistors) to work as a standalone GPS.  Basically it's now a 
stand-alone Z3811.   I have Lady Heather working with it now.   The hack of 
using the RS-422 output to directly drive a RS-232 serial port does not work 
very well with most older RS-232 receiver chips.   I have to control it with a 
USB-Serial cable.

--
If you are ever interested in playing with the Lucent boxes (Z3811, Z3812) I 
would be glad to send you a working system to play with.  Sure would like to 
use LH with it. 
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Re: [time-nuts] The home time-lab

[Bob Stewart]

Charles, I can't speak for Brooke, but I have to point out that each of us has 
different needs when it comes to powering our lab.  For myself, if I lose 
power, that's OK.  I'm retired selling a few GPSDOs here and there and working 
on some other stuff, so I don't need a 24/7 operation.  What I'd like to get 
rid of are the occasional spikes out of nowhere on my test results.  Are they 
from the power line?  From the DUT?  From the test equipment?  So, for that 
reason, I ordered a Sola xfmr.  I haven't hooked it up yet, because I was 
offered a pair of free APC Smart-UPS 700 units, sans batteries.  It seemed 
reasonable to put batteries in one and see exactly what it would do.  I've done 
a power cycle test, and later this year the power company will provide the 
source-switching tests accompanied by phase jumps and transient brownouts.  I 
suspect the UPSes won't quite stand up to that, but we'll see.  If they don't, 
then the Sola will be connected in.  If I really got serious,
  though, I think I'd look into Solar System stuff, such as an inverter, a 
lead-acid battery bank, and a suitable battery charger.  But, as I said: I'm 
retired, and the budget just isn't there to do what might be the right thing to 
get clean power 24/7/365.
Bob
 -
AE6RV.com

GFS GPSDO list:
groups.yahoo.com/neo/groups/GFS-GPSDOs/info

  From: Charles Steinmetz 
 To: time-nuts@febo.com 
 Sent: Monday, July 25, 2016 2:34 PM
 Subject: Re: [time-nuts] The home time-lab
   
Brooke wrote:

> But a relay switched UPS, like mine, does nothing to the line waveform,
> so the Sola offers a lot of improvement.
>
> Since the Sola does not help getting a sine waveform, it may be better
> to put it on the input since that might make dropout detection more
> reliable?

Instead of continuing to fiddle around with two sort-of partial 
solutions that do not actually solve the problems, why not just buy one 
or more proper online UPS boxes?  Several of us have mentioned specific 
part numbers, where you can look for them at decent prices, and how to 
maintain and care for them.

This alternative would solve decisively the problems you (and Bob) are 
seeking to solve, and the cost is not extravagant (it would be even more 
economical if you hadn't already bought the offline UPS and the CVT -- 
perhaps you can sell them to recover some of the cost).

It is details like these that distinguish a "home time lab" from "a 
bunch of test equipment in the basement."

Best regards,

Charles


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[time-nuts] Symmetricom Power On Counter

[Skip Withrow]

Hello Time-Nuts,

I just ran a Symmetricom X72 for 10 days to check the rate of the Pwr HRS
counter.  At one point I thought I did this with an SA.22c and found a
discrepancy between actual number of hours run and the counter increment.
I can report that the X72 does appear to count hours correctly.  After
running for 233 hours the hex counter incremented by 233 decimal.

This leaves me with some questions though.  The counter in the unit is four
hex digits giving a max count of 2^16 or about 65,000.  The life of the X72
is supposed to be about 20 years (roughly 180,000 hours).  So what happens
to the unit on overflow, does the counter just rollover?  So how do you
tell a new unit from one with 70,000 hours on it?  And there is also a
service bit that is supposed to switch when there are several months of
life left, what drives this bit?  Is it some kind of lamp life measurement
(like the LPRO), and is the power on counter involved in any way?

The Symmetricom X72 and SA.22c seem to be cousins, I have not played with
an X99 and don't know if it is related.  If someone has insight into these
units I would be most interested in knowing some of the answers.  In fact,
the 'w' command dumps about 26 different values (all in hex) and having the
secret decoder ring for what the item mnemonics are and the scaling of the
displayed values  would be very useful.  The user manual lists the 'w'
command but gives no information regarding the resulting display that I can
find.

Thanks in advance for any help.

Regards,
Skip Withrow
303-790-1830
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Re: [time-nuts] The home time-lab

[David]

The reason they call it a modified sine wave is that it is a square
wave with the same peak and RMS voltages as a sine wave.  Since the
RMS value of a (bipolar) square wave is equal to its peak value, it
has to include parts at zero or a lower voltage.  Some inverters use
additional voltage steps to more closely approximate a sine wave but I
think they are less common now that true sine outputs have become more
economical.

I do not know why Don Lancaster's Magic Sinewave idea is not used more
widely.  Does it have patent issues?  Maybe it is not economical
compared to a true sine output.

In the past I have used the predicable sine average responding and RMS
values of a square wave to calibrate its peak-to-peak value for use as
a calibration source.  This is useful for calibrating analog
oscilloscopes if you have an uncalibrated source but a good sine
average responding or RMS (or both for a sanity check) AC voltmeter.

On Mon, 25 Jul 2016 10:29:02 -0700, you wrote:

>Hi Chris:
>
>The APC RS1500 uses what they call modified sine wave, but I call modified 
>square wave, i.e. it's a square wave with a 
>couple of parts that are at zero volts.
>Don Lancaster promoted "Magic Sinewaves" where a pulse modulated waveform 
>drives an H-bridge.  The leading and trailing 
>edges are determined using the idea of FFT so that all the harmonics up to 
>some number (typically 9 to thirty something) 
>are zero.  There were also 3-phase versions.  But he no longer sells any 
>hardware.
>
>PS I'm looking for a source of 3-phase 400 Hz 115 VAC to power a North Finding 
>Gryo.
>http://www.prc68.com/I/WildARK2.html
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Re: [time-nuts] The home time-lab

[Hal Murray]

kb...@n1k.org said:
> If you go back far enough in time …. there is another alternative:
>Big rectifier bank, turning AC into DC, often off of multiple phases
> or sources. 
>Big DC motor running into a fairly large flywheel. 
>AC generator (or in some cases DC generators) running off of the
> shaft 

I've seen a setup with an AC motor.  Also on the shaft was a clutch and 
diesel motor.  The flywheel had to last long enough to get it started.

I remember tales of a system having troubles keeping time.  It was traced 
back to a 50-60 Hz converter box that wasn't putting out 60 Hz.  Things got 
better when they gave it a tuneup.  That was back in the '80s.  It seems 
strange now that there were power supplies that couldn't handle 50 Hz.


-- 
These are my opinions.  I hate spam.



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Re: [time-nuts] The home time-lab - APC Smart UPS 700

[Bob Stewart]

I let an older, well-aged GPSDO warm up overnight and then I ran a test with 
the UPS.  Attached were the PRS*, the GPSDO, and the 5370A.  I didn't notice 
anything when I removed power.  I did notice about a 450ps phase spike when I 
plugged the UPS back in some 640 seconds later.  But that was it: one single 
spike.  And then it was back to business as normal.  It will be interesting to 
see what happens the next time we get disturbed power here.

That 5370 consumes a Lot of power.  Someone posted instructions recently about 
swapping in a couple of bucking regulators, which I plan to try soon on one of 
my units.
*A note about the PRS.  Recently I was concerned that it had an output problem. 
 I *think* I traced it back to the proverbial "short between the headsets".  
Although the output is similar to my GPSDOs, it has a sine wave output, whereas 
my GPSDOs have a square wave output.  So, it seems that the 5370 needs a slight 
adjustment to the input levels between PRS and GPSDO.

Bob
 -
AE6RV.com

GFS GPSDO list:
groups.yahoo.com/neo/groups/GFS-GPSDOs/info



  
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Re: [time-nuts] The home time-lab

[bownes]

Or the current version:

Large AC motor driving a LARGE flywheel with an AC (and/or -48VDC) generator on 
the other side feeding a very large battery plant. If mains drops more than 1/2 
cycle it connects the turbine and starts it up. 

We had a 5MW one at $OLD_GIG for feeding our supercomputer factory. 

It was rumored that at least one customer location kept one of their turbines 
(redundant) idling at all times because they could not afford to loose a data 
set. 



> On Jul 25, 2016, at 09:55, Bob Camp  wrote:
> 
> Hi
> 
> If you go back far enough in time …. there is another alternative:
> 
>   Big rectifier bank, turning AC into DC, often off of multiple phases or 
> sources. 
> 
>   Big DC motor running into a fairly large flywheel. 
> 
>   AC generator (or in some cases DC generators) running off of the shaft
> 
>   A tuning fork (yes state of the art timing) based control on the AC 
> output frequency  
> 
>   A saturated reactor control loop on the generator side, same thing on 
> the motor side.
> 
> Wonderfull stuff. State of the art UPS for your shipboard computer in 1962. 
> Ear muffs anyone? 
> 
> Bob
> 
> 
> 
>> On Jul 25, 2016, at 8:39 AM, Charles Steinmetz  wrote:
>> 
>> Chris wrote:
>> 
>>> I've never thought UPS were a good idea for anything but a computer
>>> that needs to shut down gracefully.   For your use you need something
>>> that cleans up the AC mains power.
>> 
>> A proper "online" (or "double conversion") UPS does just that.  It always 
>> provides cleanly-generated sine-wave power from a DC-AC converter.  Most 
>> will even deliver crystal-controlled power (i.e., non-synchronous with the 
>> AC line) in several frequency increments, if you desire, as well as a choice 
>> of regulated output voltages.  (For obvious reasons, they are usually 
>> operated synchronously.)
>> 
>> They are *much* more effective than ferroresonant supplies at removing 
>> glitches from the mains supply.
>> 
>> You must be referring to "offline" backup supplies.
>> 
>> Best regards,
>> 
>> Charles
>> 
>> 
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Re: [time-nuts] Venus838LPx-T opinions?

[Bill Riches]

Hi Mark,

If you are ever interested in playing with the Lucent boxes (Z3811, Z3812) I 
would be glad to send you a working system to play with.  Sure would like to 
use LH with it.

73,

Bill, WA2DVU
Cape May, NJ

-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Mark Sims
Sent: Sunday, July 24, 2016 7:34 PM
To: time-nuts@febo.com
Subject: [time-nuts] Venus838LPx-T opinions?

The closest thing to an official Lady Heather site if John Mile's ke5fx.com
I also want to put it it up on Github when the code settles down some.

The good Lady Heather doesn't accept donations of the monetary kind.   
Receivers not currently hoarded in her dungeon are appreciated.  Particularly 
interested in RFTG-M,  Z3805. Z3815, Z3816, and HP53xxx at the moment (or 
somebody to test them).  Code is in there for working with these, but it has 
never been tested on a real device (and SCPI tends to be rather picky about 
just how you have to talk to it).

---
Questions still remain:

1) What is the link to the "official" Lady Heather site?
2) How/where can we shoot a donation to say "Thanks!"?


  
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Re: [time-nuts] The home time-lab

[Brooke Clarke]

Hi Chris:

The APC RS1500 uses what they call modified sine wave, but I call modified square wave, i.e. it's a square wave with a 
couple of parts that are at zero volts.
Don Lancaster promoted "Magic Sinewaves" where a pulse modulated waveform drives an H-bridge.  The leading and trailing 
edges are determined using the idea of FFT so that all the harmonics up to some number (typically 9 to thirty something) 
are zero.  There were also 3-phase versions.  But he no longer sells any hardware.


PS I'm looking for a source of 3-phase 400 Hz 115 VAC to power a North Finding 
Gryo.
http://www.prc68.com/I/WildARK2.html

--
Have Fun,

Brooke Clarke
http://www.PRC68.com
http://www.end2partygovernment.com/2012Issues.html
The lesser of evils is still evil.

 Original Message 

Yes, "ferroresonant" is also called CVT.  Typically rather than buying
just the transformer you buy a box that has one in it but also some
other components to clip spikes (some MOVs) and and LC low pass
filter.  I know it seems a saturated core might produce a non-sine
wave but current CVTs have very low distortion.

The other option is an on-line UPS, one that always runs off the
battery.  These are expensive  if you need a good sine wave output.
The UPS has an output stage not unlike an audio amplifier.  Not nearly
as efficient as MOSFET switches.  (question:  I'd guess that modern
versions would be designed with class-D output stages and have decent
power efficiency??)

The best solution is what the phone companies did.  The telco style
equipment, like computers and such runs off 48VDC. and batteries are
connected in parallel from a "battery room".  If designing your own
GPSDO, it should be built to run of 12V battery power.

For AC the best solution is a motor generator.  Basically an iron
flywheel rides out any small dropouts in the utility power.  They had
one for a mainframe computer at a place I worked at a long time ago.
But only that one output 280V at 400Hz as the computer required 400Hz
power.



On Mon, Jul 25, 2016 at 2:43 AM, David J Taylor
 wrote:


Chris,
Do you mean like these:

  http://www.aelgroup.co.uk/products/agt.php

I have an old 75W unit somewhere





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Re: [time-nuts] [LEAPSECS] Leap second to be introduced at midnight UTC December 31 this year

[Bob Camp]

Hi


> On Jul 25, 2016, at 10:21 AM, Martin Burnicki  
> wrote:
> 
> Bob,
> 
> Bob Camp wrote:
>> Hi
>> 
>> The practical problem with any change to leap seconds is transition from 
>> what we have
>> to the “new system”. Anything other than dropping them altogether involves a 
>> *lot* of 
>> coordination. You pretty much have to pick a date and bring everything onto 
>> the new
>> standard then. For testing purposes your time sources should “advertise” the 
>> new 
>> information ahead of that date. As a practical point, that means a new field 
>> in the data. 
>> In the case of GPS and other space based systems, that’s not going to 
>> happen. 
> 
> But if you
> 
> - stick with the leap seconds with UTC as-is
> - let the kernel alternatively run on TAI instead of UTC
> - keep existing API calls as they are, returning UTC
> - introduce new API calls which tell if the kernel runs UTC or TAI
>  and let you query the TAI time stamps
> 
> then both kernels and applications could make a change over to the new
> timekeeping seamlessly.
> 
> I agree this wouldn't fix all problems you may have with leap seconds,
> but it would at least avoid problems like "the kernel hangs when the
> system time is stepped back by 1 s to account for a leap second”.

Except that you still have the issue of “what time did this file get changed”. 
To most of us, that’s not 
really a big deal. A second either way … who cares. :) In some areas they care 
a *LOT* and a second
is a really big deal. Having two different time stamps running around in the 
same kernel with different 
people picking which one to use …. sounds like a recipe for trouble. 

Now, having the “new” calls ahead of the transition, yes, that’s pretty much 
mandatory. You do need to 
debug this stuff and it has to be done somehow. If we are talking about the 
original suggestion, it’s a one
second delta one way or the other. There is nothing going on below the second 
level. I suppose you *could*
have more than one second, but it seems unlikely. In that case, your call is 
pretty simple “give me the delta”. 
Seems fairly easy / safe. I’ve messed up things that are far simpler :) 

Bob

> 
> Martin
> 
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Re: [time-nuts] The home time-lab

[David]

I have never seen one which did not use a class-D output with L-C
filtering.  Total efficiency is in the 84 to 92 percent range.

These days they also include power factor correction on their line
input so they can be used to apply power factor correction to any
load.

Refurbished ones are available online for reasonable prices.

Another option if you just want superior line filtering is an active
power conditioner which is an online UPS using a capacitor bank
instead of batteries.  They should be less expensive since they do not
have the large impedance jump down to 48 volts but in practice they
are not because of a small market compared to online UPSes.  Some
online UPSes will operate this way without batteries.

On Mon, 25 Jul 2016 08:28:45 -0700, you wrote:

>...
>
>The other option is an on-line UPS, one that always runs off the
>battery.  These are expensive  if you need a good sine wave output.
>The UPS has an output stage not unlike an audio amplifier.  Not nearly
>as efficient as MOSFET switches.  (question:  I'd guess that modern
>versions would be designed with class-D output stages and have decent
>power efficiency??)
>
>...
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Re: [time-nuts] The home time-lab

[Brooke Clarke]

Hi Bill:

I have links to the Sola patents at: 
http://www.prc68.com/I/Sola_CVS.html#Patents
The 1939 patent shows a single gap and the resonant circuit, but the current patent (number on Sola xformer label) shows 
two gaps and the resonant circuit.

They specify up to a 3 ms dropout restoration which implies the amount of 
energy stored is enough to last that long.

A full time UPS (one where the line is converted to battery voltage then battery voltage is converted to a sine wave) 
could be expected to have a clean output.

But a relay switched UPS, like mine, does nothing to the line waveform, so the 
Sola offers a lot of improvement.

Since the Sola does not help getting a sine waveform, it may be better to put it on the input since that might make 
dropout detection more reliable?


--
Have Fun,

Brooke Clarke
http://www.PRC68.com
http://www.end2partygovernment.com/2012Issues.html
The lesser of evils is still evil.

 Original Message 

Years ago I knew exactly how Sola regulators worked. That has faded, but
what remains is that the regulation was done by varying the saturation
of the core. That's why there is a slot in the laminations. I find it
hard to believe that a partially saturated core can produce zero
harmonics.

In any event, the LC circuit does not filter anything. Possibly the
circuit counteracts the change in saturation as the line voltage
changes. I wouldn't expect it to effect the high frequency components of
spikes.

Any power supply that has a diode bridge and capacitor to create DC only
draws power from the line at the voltage peaks, when the diodes become
forward biased. I don't know of any choke input supplies, as were used
to reduce the peak current of vacuum tube rectifiers.

I know nothing about power factor correction for a bridge and capacitor,
whether or not it is followed by a switching regulator.

Make of it what you will.

Bill Hawkins


-Original Message-
From: Alex Pummer
Sent: Sunday, July 24, 2016 7:29 PM

That is interesting, since the Sola device has a to the line frequency
tuned tank circuit in it, thus the output should not have to many higher
harmonics and should look reasonable close to sinusoidal see here:
http://www.rdrelectronics.com/russ/jun16/vs2.PDF

73, K6UHN Alex


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Re: [time-nuts] The home time-lab

[Scott McGrath]

Charles is correct and most data centers and metrology laboratories operate 
from power produced by large versions of these systems i.e. From 50KW to 
megawatts generally backed by one or more generators to carry facility when 
utility power is not available 

Content by Scott
Typos by Siri

> On Jul 25, 2016, at 8:39 AM, Charles Steinmetz  wrote:
> 
> Chris wrote:
> 
>> I've never thought UPS were a good idea for anything but a computer
>> that needs to shut down gracefully.   For your use you need something
>> that cleans up the AC mains power.
> 
> A proper "online" (or "double conversion") UPS does just that.  It always 
> provides cleanly-generated sine-wave power from a DC-AC converter.  Most will 
> even deliver crystal-controlled power (i.e., non-synchronous with the AC 
> line) in several frequency increments, if you desire, as well as a choice of 
> regulated output voltages.  (For obvious reasons, they are usually operated 
> synchronously.)
> 
> They are *much* more effective than ferroresonant supplies at removing 
> glitches from the mains supply.
> 
> You must be referring to "offline" backup supplies.
> 
> Best regards,
> 
> Charles
> 
> 
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Re: [time-nuts] The home time-lab

[Chris Albertson]

Yes, "ferroresonant" is also called CVT.  Typically rather than buying
just the transformer you buy a box that has one in it but also some
other components to clip spikes (some MOVs) and and LC low pass
filter.  I know it seems a saturated core might produce a non-sine
wave but current CVTs have very low distortion.

The other option is an on-line UPS, one that always runs off the
battery.  These are expensive  if you need a good sine wave output.
The UPS has an output stage not unlike an audio amplifier.  Not nearly
as efficient as MOSFET switches.  (question:  I'd guess that modern
versions would be designed with class-D output stages and have decent
power efficiency??)

The best solution is what the phone companies did.  The telco style
equipment, like computers and such runs off 48VDC. and batteries are
connected in parallel from a "battery room".  If designing your own
GPSDO, it should be built to run of 12V battery power.

For AC the best solution is a motor generator.  Basically an iron
flywheel rides out any small dropouts in the utility power.  They had
one for a mainframe computer at a place I worked at a long time ago.
But only that one output 280V at 400Hz as the computer required 400Hz
power.



On Mon, Jul 25, 2016 at 2:43 AM, David J Taylor
 wrote:

> Chris,
> Do you mean like these:
>
>  http://www.aelgroup.co.uk/products/agt.php
>
> I have an old 75W unit somewhere
>


-- 

Chris Albertson
Redondo Beach, California
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Re: [time-nuts] [LEAPSECS] Leap second to be introduced at midnight UTC December 31 this year

[Martin Burnicki]

Bob,

Bob Camp wrote:
> Hi
> 
> The practical problem with any change to leap seconds is transition from what 
> we have
> to the “new system”. Anything other than dropping them altogether involves a 
> *lot* of 
> coordination. You pretty much have to pick a date and bring everything onto 
> the new
> standard then. For testing purposes your time sources should “advertise” the 
> new 
> information ahead of that date. As a practical point, that means a new field 
> in the data. 
> In the case of GPS and other space based systems, that’s not going to happen. 

But if you

- stick with the leap seconds with UTC as-is
- let the kernel alternatively run on TAI instead of UTC
- keep existing API calls as they are, returning UTC
- introduce new API calls which tell if the kernel runs UTC or TAI
  and let you query the TAI time stamps

then both kernels and applications could make a change over to the new
timekeeping seamlessly.

I agree this wouldn't fix all problems you may have with leap seconds,
but it would at least avoid problems like "the kernel hangs when the
system time is stepped back by 1 s to account for a leap second".

Martin

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Re: [time-nuts] The home time-lab

[Bob Camp]

Hi

If you go back far enough in time …. there is another alternative:

   Big rectifier bank, turning AC into DC, often off of multiple phases or 
sources. 

   Big DC motor running into a fairly large flywheel. 

   AC generator (or in some cases DC generators) running off of the shaft

   A tuning fork (yes state of the art timing) based control on the AC 
output frequency  

   A saturated reactor control loop on the generator side, same thing on 
the motor side.

Wonderfull stuff. State of the art UPS for your shipboard computer in 1962. Ear 
muffs anyone? 

Bob



> On Jul 25, 2016, at 8:39 AM, Charles Steinmetz  wrote:
> 
> Chris wrote:
> 
>> I've never thought UPS were a good idea for anything but a computer
>> that needs to shut down gracefully.   For your use you need something
>> that cleans up the AC mains power.
> 
> A proper "online" (or "double conversion") UPS does just that.  It always 
> provides cleanly-generated sine-wave power from a DC-AC converter.  Most will 
> even deliver crystal-controlled power (i.e., non-synchronous with the AC 
> line) in several frequency increments, if you desire, as well as a choice of 
> regulated output voltages.  (For obvious reasons, they are usually operated 
> synchronously.)
> 
> They are *much* more effective than ferroresonant supplies at removing 
> glitches from the mains supply.
> 
> You must be referring to "offline" backup supplies.
> 
> Best regards,
> 
> Charles
> 
> 
> ___
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Re: [time-nuts] The home time-lab

[Charles Steinmetz]

Chris wrote:


I've never thought UPS were a good idea for anything but a computer
that needs to shut down gracefully.   For your use you need something
that cleans up the AC mains power.


A proper "online" (or "double conversion") UPS does just that.  It 
always provides cleanly-generated sine-wave power from a DC-AC 
converter.  Most will even deliver crystal-controlled power (i.e., 
non-synchronous with the AC line) in several frequency increments, if 
you desire, as well as a choice of regulated output voltages.  (For 
obvious reasons, they are usually operated synchronously.)


They are *much* more effective than ferroresonant supplies at removing 
glitches from the mains supply.


You must be referring to "offline" backup supplies.

Best regards,

Charles


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Re: [time-nuts] NCOCXO anyone?

[Bob Camp]

Hi

A typical double oven design runs about 10 mw or so in the circuitry 
in the inner oven. The “stuff” inside the outer oven likely doubles that 
number. 
The rest of the circuit is put outside the outer oven to reduce heat rise. There
could be another 40 mw in that part of the circuit. Everything else is 
controlled 
power to heat things and will go to zero at the highest temperature. 

If you run the inner oven at an offset of 3 to 5 C from the outer, the inner
heater will likely not pull more than 40 mw and may pull quite a bit less.

Bob


> On Jul 24, 2016, at 4:45 PM, James Flynn  wrote:
> 
> Richard (Rick) Karlquist  writes:
> 
> 
>> The last thing you want in an oven is a lot of
>> added thermal overhead, especially in a double oven
>> where you already fighting against running out of
>> temperature range.  If you want to ovenize everything
>> but the kitchen sink, put it in it's own oven that is
>> separate from the crystal oven.
> 
> The thermal overhead is quite small compared to the power required for 
> the outer oven to hold temperature.  80mW maximum as opposed to about 1 
> watt.
> 
> I did a comparison of the temperature rise of running the unit 
> essentially as a single, inner oven with the rest of the electronics 
> mentioned in the outer "box", and then turning on the outer heater.  The 
> Q from the inner oven was far and away the dominant factor.
> 
> Putting the DAC inside the outer oven was the obvious solution for me, 
> as opposed to putting them outside in ambient.  I did consider thermal 
> compensation, but again the outer oven would be able to keep things 
> within a fraction of a degree over the range of normal ambient in the 
> lab. 
> 
> Separate ovens seems to be inviting noise getting into the signal lines 
> between the two ovens.  
> 
>> 
>> I also don't like intermingling digital signals with the
>> analog oscillator signal.
> 
> Not sure what you mean by "intermingling". There are separate ground 
> returns for the oscillator output (transformer isolated) and the digital 
> signals. There is a low pass filter between DAC and oscillator control 
> to minimize noise getting across. Also digital circuits and oscillator 
> have their own individual precision regulators.
> 
>> 
>> Have you measured the thermal gain of your outer oven?
>> I suspect it's not much.  You could use inner oven
>> current draw as a proxy.
> 
> I did a while ago and remember it was on the order of 50 - 100. But I 
> have changed the design somewhat and should do it again when the 
> experiment gets going.
> 
> 
> 
> 
> 
> 
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Re: [time-nuts] Precision DACs (was: NCOCXO anyone?)

[David]

The AD5791 specifications under various conditions are all roughly
consistent; 20 bits at DC, 16 bits at 10 ksps based on SFDR, and 12
bits at 1 Msps for large code changes.

Its intended application is DC where its 1 Msps update rate applies
for code steps of 500 or smaller and settling time will be within 1
LSB.

On Sun, 24 Jul 2016 23:48:05 -0400, you wrote:

>I doubt the AD5791 does much better than 16 bits operating at 1 Msps, when
>you include glitch energy, noise, and distortion.
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Re: [time-nuts] The home time-lab

[David J Taylor]

But then you may find that you can NEVER finish a test.  The AC line
is typically full of transients.

I've never thought UPS were a good idea for anything but a computer
that needs to shut down gracefully.   For your use you need something
that cleans up the AC mains power.  The best ones have a ferroresonant
transformer inside and will hand those few millisecond glitches.

Chris Albertson
Redondo Beach, California
___

Chris,
Do you mean like these:

 http://www.aelgroup.co.uk/products/agt.php

I have an old 75W unit somewhere

Cheers,
David
--
SatSignal Software - Quality software written to your requirements
Web: http://www.satsignal.eu
Email: david-tay...@blueyonder.co.uk
Twitter: @gm8arv
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Re: [time-nuts] The home time-lab

[Alexander Pummer]

you could bring the horse to the well.


On 7/24/2016 7:36 PM, Bill Hawkins wrote:

Years ago I knew exactly how Sola regulators worked. That has faded, but
what remains is that the regulation was done by varying the saturation
of the core. That's why there is a slot in the laminations. I find it
hard to believe that a partially saturated core can produce zero
harmonics.

In any event, the LC circuit does not filter anything. Possibly the
circuit counteracts the change in saturation as the line voltage
changes. I wouldn't expect it to effect the high frequency components of
spikes.

Any power supply that has a diode bridge and capacitor to create DC only
draws power from the line at the voltage peaks, when the diodes become
forward biased. I don't know of any choke input supplies, as were used
to reduce the peak current of vacuum tube rectifiers.

I know nothing about power factor correction for a bridge and capacitor,
whether or not it is followed by a switching regulator.

Make of it what you will.

Bill Hawkins


-Original Message-
From: Alex Pummer
Sent: Sunday, July 24, 2016 7:29 PM

That is interesting, since the Sola device has a to the line frequency
tuned tank circuit in it, thus the output should not have to many higher
harmonics and should look reasonable close to sinusoidal see here:
http://www.rdrelectronics.com/russ/jun16/vs2.PDF

73, KJ6UHN Alex


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Re: [time-nuts] The home time-lab

[Chris Albertson]

On Thu, Jul 7, 2016 at 6:54 PM, Bob Stewart  wrote:
> So, since I need to power the 5370 (preferably both) I'm looking at a deep 
> cycle battery, a charger, and an inverter?  At this point in the process, a 
> power line monitor is looking like a good solution.  At least it would tell 
> me to ignore the test results.

But then you may find that you can NEVER finish a test.  The AC line
is typically full of transients.

I've never thought UPS were a good idea for anything but a computer
that needs to shut down gracefully.   For your use you need something
that cleans up the AC mains power.  The best ones have a ferroresonant
transformer inside and will hand those few millisecond glitches.



-- 

Chris Albertson
Redondo Beach, California
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Re: [time-nuts] Precision DACs (was: NCOCXO anyone?)

[Scott Stobbe]

I doubt the AD5791 does much better than 16 bits operating at 1 Msps, when
you include glitch energy, noise, and distortion.

On Saturday, 23 July 2016, Attila Kinali  wrote:

> On Fri, 22 Jul 2016 12:15:25 -0500
> David > wrote:
>
> > If you expect analog specifications in line with the claimed digital
> > resolution of ADCs and DACs, you will be disappointed.  20 bits is
> > about where they top out no matter how many bits are available; the
> > best you can hope for is that they are monotonic but how meaningful is
> > that when it is buried in noise?
>
> Depends on your application. If the circuitry that follows the DAC has
> some integrative/low-pass characteristics, then bits burried in noise
> might be not that bad. E.g. when controlling an VCXO, any noise beyond
> 10-50kHz will be filtered out by the crystal and its high Q.
>
> Similarly, low frequency noise might be eaten up by the surrounding
> control-loop. This is especially beneficial when dealing with a
> circuit that has high 1/f noise. The drawback is, that high loop frequency
> (something around 10-100Hz is the minimum required to filter 1/f noise)
> is not that easy to achieve. It requires carefull design and makes things
> generally a lot more expensive.
>
> > The LTC2400 is considered suitable for 6 digit designs before software
> > calibration is used which the application note and datasheet mention.
> > In this case, it is its repeatable INL which can be corrected for and
> > its low gain and offset drift which matter.
>
> Yes, but the LTC2400, as all delta-sigma converters, has the big problem
> that it only reaches the full performance at a very low sampling rate.
> In case of the LTC2400 it's a whooping 7sps. Ie, that would limit the
> DAC build with an LTC2400 in its feedback path to at most 3sps, probably
> even lower.
>
> On the other hand, a modern DACs like the AD5791 reaches full 20bit at
> 1Msps
> (resp 1us settling time to 0.02% @10V step, or 1us to 1LSB @500 code step).
> But using the AD5791 in a design isn't easy either. The dual voltage
> reference
> that is required to reach full spec is kind of inconvenient. And as phk
> already
> wrote, these DACs deliver you the reference accuracy and noise very
> precisely.
>
> A nice write-up on issues in this area can be found at[1]
>
> Attila Kinali
>
>
> [1] "The 20-Bit DAC Is the Easiest Part of a 1-ppm-Accurate Precision
> Voltage Source", by Maurice Egan, 2010
> http://www.analog.com/library/analogdialogue/archives/44-04/ad5791.html
>
>
> --
> Malek's Law:
> Any simple idea will be worded in the most complicated way.
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