Re: [time-nuts] HP5065A C-field current voltage mod

[Poul-Henning Kamp]

My HP5065 adventures continue...

http://phk.freebsd.dk/hacks/HP5065A/20150908_a15/index.html


-- 
Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
p...@freebsd.org | TCP/IP since RFC 956
FreeBSD committer   | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.
___
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.

Re: [time-nuts] HP5065A C-field current voltage mod

[Perry Sandeen via time-nuts]

Hi,

 Wrote:No, the temperature is not stable, not even close.

 Wrote:Given that the TL431 is quite good at measuring temperature, that makes 
itunsuitable in this case.

 Wrote:There is a LOT more to making a good temperature-controlled 
>environmentthan hacking together a DIY oven.  Thatmay be fine for stability of 
tenths of a percent (10e-3), but when stability of

>10e-13is at issue it doesn't pay to start with 50ppm parts and put them in a 
>DIYoven.  You need to start with low-tempcoparts.

 Waita second good people! We have a bit of confusion about what I wrote.

 Anamplification of what I wrote:

 TheTL 431 is listed as a low noise shunt regulator.  It doesn’t measure 
temperature at all. Theonly noise spec I could find is about 7 uV. A LM723 data 
sheet specified 2.5 uV noise. The REF 012A specifies 5 uVnoise. The first two 
are around 50 cents from Mouser.  The REF102A is about 10X more.

I’mnot sure the original reference diode had that low noise but that’s a guess 
onmy part.

 Thetemperature circuit I referenced uses a 220 ohm load resistor in series 
withthe positive output of the regulator and Vcc. The temperature is regulated 
by a resistor from Vcc to the programminglead. Then there is a thermistor going 
from the programming lead to ground.

 Usingthe formula given in the data sheet. One can then calculate the desired 
voltageratio and then with a series control pot set the temp to the desired 
value.

 Thisis a simple circuit and with 1% 100ppm vishey metal film resistors it 
would begood for .1 degree stability. That should suffice for Paul’s application

 Charlesis correct that if one is getting into the TN class of .01 or .001 
degreestability a far more elaborate circuit is required.

 Goingback to my original post, this was only a suggestion for an 
inexpensivesolution for the problem. Since I don’t have a 5065A, I can’t prove 
or disproveif it would give the desired results.

 WhenI get them set up, my demon to solve is how to get my 5370B’s to be cool 
andquiet. There has to be a better solution to the PS heat.

 Regards,

 Perrier

___
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.

Re: [time-nuts] HP5065A C-field current voltage mod

[Poul-Henning Kamp]

In message <1557706566.2101400.1441521513941.javamail.ya...@mail.yahoo.com>, Pe
rry Sandeen via time-nuts writes:

> TheTL 431 is listed as a low noise shunt regulator.  It doesn’t
>measure temperature at all. Theonly noise spec I could find is about
>7 uV. A LM723 data sheet specified 2.5 uV noise. The REF 012A
>specifies 5 uVnoise. The first two are around 50 cents from Mouser. 
>The REF102A is about 10X more.

Stuff like that seldom happen by chance :-)

TL431 is amazing and very versatile, but it does not look like the
right solution to me in this case.

-- 
Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
p...@freebsd.org | TCP/IP since RFC 956
FreeBSD committer   | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.
___
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.

Re: [time-nuts] HP5065A C-field current voltage mod

[Bob Camp]

Hi

Going back to the original math:

The objective is a device that is stable to about 3 ppm and has a noise level 
of  << 3 ppm (if possible). Ideally 
one would want to get below 1 ppm on both numbers.  

 A TL431 has a noise level of roughly 5 to 15 uV (depending on your sample) 
running at 2.5V. That puts it’s 
noise level at 2 to 6 ppm. 

If you take a look at the noise plots on the TI data sheet it’s pretty apparent 
that the bulk of the noise is at very 
low frequencies. Noise is climbing by the time you hit 100Hz and it’s at 220 nV 
/ sqrt(Hz) by the time you get to 10 Hz.
They don’t plot it below there, but the curve is moving up at a pretty good 
rate at 10 Hz. The 0.1 to 10 Hz plot in the
same sheet shows a pretty active process going on. 

There are other parts out there with the same output voltage that have a *lot* 
less noise:

http://www.linear.com/product/LTC6655

Yes, they do cost more money. 

Bob

> On Sep 6, 2015, at 2:38 AM, Perry Sandeen via time-nuts  
> wrote:
> 
> Hi,
> 
>  Wrote:No, the temperature is not stable, not even close.
> 
>  Wrote:Given that the TL431 is quite good at measuring temperature, that 
> makes itunsuitable in this case.
> 
>  Wrote:There is a LOT more to making a good temperature-controlled 
> >environmentthan hacking together a DIY oven.  Thatmay be fine for stability 
> of tenths of a percent (10e-3), but when stability of
> 
>> 10e-13is at issue it doesn't pay to start with 50ppm parts and put them in a 
>> DIYoven.  You need to start with low-tempcoparts.
> 
>  Waita second good people! We have a bit of confusion about what I wrote.
> 
>  Anamplification of what I wrote:
> 
>  TheTL 431 is listed as a low noise shunt regulator.  It doesn’t measure 
> temperature at all. Theonly noise spec I could find is about 7 uV. A LM723 
> data sheet specified 2.5 uV noise. The REF 012A specifies 5 uVnoise. The 
> first two are around 50 cents from Mouser.  The REF102A is about 10X more.
> 
> I’mnot sure the original reference diode had that low noise but that’s a 
> guess onmy part.
> 
>  Thetemperature circuit I referenced uses a 220 ohm load resistor in series 
> withthe positive output of the regulator and Vcc. The temperature is 
> regulated by a resistor from Vcc to the programminglead. Then there is a 
> thermistor going from the programming lead to ground.
> 
>  Usingthe formula given in the data sheet. One can then calculate the desired 
> voltageratio and then with a series control pot set the temp to the desired 
> value.
> 
>  Thisis a simple circuit and with 1% 100ppm vishey metal film resistors it 
> would begood for .1 degree stability. That should suffice for Paul’s 
> application
> 
>  Charlesis correct that if one is getting into the TN class of .01 or .001 
> degreestability a far more elaborate circuit is required.
> 
>  Goingback to my original post, this was only a suggestion for an 
> inexpensivesolution for the problem. Since I don’t have a 5065A, I can’t 
> prove or disproveif it would give the desired results.
> 
>  WhenI get them set up, my demon to solve is how to get my 5370B’s to be cool 
> andquiet. There has to be a better solution to the PS heat.
> 
>  Regards,
> 
>  Perrier
> 
> ___
> 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.

Re: [time-nuts] HP5065A C-field current voltage mod

[Magnus Danielson]

Hi,

On 09/04/2015 11:37 PM, Poul-Henning Kamp wrote:


In message <89828.1441376...@critter.freebsd.dk>, "Poul-Henning Kamp" writes:


I actually have some calculations relevant to this, I'll write them
up on my homepage when I have a second.


Here:

http://phk.freebsd.dk/hacks/HP5065A/20150904_math

I'd be very pleased if somebody would double-check the calculations.



The math looks OK. The approximation due to non-linearity is probably 
OKish for getting the sizes right.


If I get a reply from Corby, I might get up to speed to upgrade my 
5065s, and then upgrading C-field and PSU as well.


Cheers,
Magnus
___
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.

Re: [time-nuts] HP5065A C-field current voltage mod

[Poul-Henning Kamp]

In message <04c901d0e762$210659e0$63130da0$@miles.io>, "John Miles" writes:

>I have to wonder if the Implementers mistakenly blamed the RVFR
>for drift in some other component.

When I got my 5065A, it had a very obvious and consistent drift of
-3e-13/day.   The MDEV turns upwards around 100k seconds.

However, that was right after I received the unit and replaced the
OCXO, so it may be the front end of a bath-tub curve and not indicative
of the drift once the unit got properly "burned in".

In my current run, at 470.000 seconds (5.5 days), with the Fluke
732+resistor C-field driver, there is no sign of any drift yet.

So yes, it may not be the RVFR that's drifting (most) and that just
makes this game even more fun...

-- 
Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
p...@freebsd.org | TCP/IP since RFC 956
FreeBSD committer   | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.
___
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.

Re: [time-nuts] HP5065A C-field current voltage mod

[Charles Steinmetz]

Perry wrote:

OK, but why?  The temperature would be stable so the resistorsand 
reference diode wouldn't drift.


There is a LOT more to making a good temperature-controlled 
environment than hacking together a DIY oven.  That may be fine for 
stability of tenths of a percent (10e-3), but when stability of 
10e-13 is at issue it doesn't pay to start with 50ppm parts and put 
them in a DIY oven.  You need to start with low-tempco parts.



What about newer reference's IC's such as REF 102?
I don't want to re-invent thewheel, just learn what is better.


You need to spend time researching the tolerance, noise, and tempcos 
of two- and three-terminal voltage references.  The manufacturers 
have on-line selection guides that allow you to sort products by any 
parameter you choose.  Most distributors do, too.  Or, look at a 
reference that has done much of it for you -- I suggest the new, 
third edition of The Art of Electronics, which has table after table 
of the very information you are looking for.


Best regards,

Charles



___
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.

Re: [time-nuts] HP5065A C-field current voltage mod

[Poul-Henning Kamp]

In message <20150904152721.rkie3...@smtp14.mail.yandex.net>, Charles Steinmetz 
writes:
>Perry wrote:
>
>>OK, but why?  The temperature would be stable so the resistorsand 
>>reference diode wouldn't drift.
>
>There is a LOT more to making a good temperature-controlled 
>environment than hacking together a DIY oven.  That may be fine for 
>stability of tenths of a percent (10e-3), but when stability of 
>10e-13 is at issue it doesn't pay to start with 50ppm parts and put 
>them in a DIY oven.  You need to start with low-tempco parts.

I actually have some calculations relevant to this, I'll write them
up on my homepage when I have a second.

The short version is that voltage reference noise above 5PPM will
be a limiting factor on performance.

-- 
Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
p...@freebsd.org | TCP/IP since RFC 956
FreeBSD committer   | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.
___
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.

Re: [time-nuts] HP5065A C-field current voltage mod

[Poul-Henning Kamp]

In message <89828.1441376...@critter.freebsd.dk>, "Poul-Henning Kamp" writes:

>I actually have some calculations relevant to this, I'll write them
>up on my homepage when I have a second.

Here:

http://phk.freebsd.dk/hacks/HP5065A/20150904_math

I'd be very pleased if somebody would double-check the calculations.

-- 
Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
p...@freebsd.org | TCP/IP since RFC 956
FreeBSD committer   | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.
___
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.

Re: [time-nuts] HP5065A C-field current voltage mod

[John Miles]

One idea would be to leave the existing C-field circuit in place with a switch 
to disable it.  That'd preserve your ability to carry out the second harmonic 
adjustment procedure, while allowing you to switch back to a stable current for 
normal operation.

For that matter, it's not clear what "aging process in the A12 RVFR assembly" 
accounts for the presence of that adjustment procedure in the manual.  Given 
the absence of any other aging mechanisms other than (very) gradual lamp 
darkening, I have to wonder if the Implementers mistakenly blamed the RVFR for 
drift in some other component.  I suppose they could be referring to partial 
diffusion of the buffer gas through the cell walls... but after 40 years, is 
there any indication that this is actually an issue?

Has anyone looked into the oven temperature stability to make sure that further 
optimization of C-field stability is worthwhile?  I'm a bit behind on my email 
so this may have already come up.

-- john, KE5FX
Miles Design LLC


> -Original Message-
> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Poul-
> Henning Kamp
> Sent: Friday, September 04, 2015 2:38 PM
> To: Discussion of precise time and frequency measurement
> Subject: Re: [time-nuts] HP5065A C-field current voltage mod
> 
> 
> In message <89828.1441376...@critter.freebsd.dk>, "Poul-Henning Kamp"
> writes:
> 
> >I actually have some calculations relevant to this, I'll write them
> >up on my homepage when I have a second.
> 
> Here:
> 
>   http://phk.freebsd.dk/hacks/HP5065A/20150904_math
> 
> I'd be very pleased if somebody would double-check the calculations.
> 
> --
> Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
> p...@freebsd.org | TCP/IP since RFC 956
> FreeBSD committer   | BSD since 4.3-tahoe
> Never attribute to malice what can adequately be explained by incompetence.
> ___
> 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.