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

[Perry Sandeen via time-nuts]

Hi,


 
Wrote: A possible solution mightbe to use two of the TL431 programmable shut 
regulators. [Snip]


 
Wrote: That would be worse thanwhat is in my 5065 now.


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


 
Is the TL 431 not sufficientlyquiet? What about newer reference’s IC’s such as 
REF 102?


 
I don’t want to re-invent thewheel, just learn what is better.


 
Regards,


 
Perrier

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

[Poul-Henning Kamp]

In message <1530394039.1439027.1441348869239.javamail.ya...@mail.yahoo.com>, Pe
rry Sandeen writes:

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

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

Given that the TL431 is quite good at measuring temperature, that
makes it unsuitable in this case.

I have identified one source of the temperature fluctuations:  The
series pass transistor of the +20V rail is located right beneath
the A15 PCB, so any variation in mains (or EXT DC) voltage causes
the A15 temperature to change accordingly.

More details here:

http://phk.freebsd.dk/hacks/HP5065A/20150903_psu/


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

[Chuck Harris]

Are you sure?  Perry was proposing to use a TL431 to
make an oven, using its famous temperature sensitivity,
and inside the oven would be another TL431 that acted
as a voltage reference.

Every oven I have ever seen that is temperature controlled
has a part that is quite good at measuring temperature at
the helm.

-Chuck Harris

Poul-Henning Kamp wrote:


In message <1530394039.1439027.1441348869239.javamail.ya...@mail.yahoo.com>, Pe
rry Sandeen writes:


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


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

Given that the TL431 is quite good at measuring temperature, that
makes it unsuitable in this case.

I have identified one source of the temperature fluctuations:  The
series pass transistor of the +20V rail is located right beneath
the A15 PCB, so any variation in mains (or EXT DC) voltage causes
the A15 temperature to change accordingly.

More details here:

http://phk.freebsd.dk/hacks/HP5065A/20150903_psu/



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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



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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.
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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.
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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.

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[time-nuts] HP 3048A Alternative to HP3561A?

[John Allen]

Hello all - I have always wanted an HP 3048A system.  I have acquired a
11848A, but need an HP 3561A or equivalent.
 
Is there any substitute to the 3561A?
 
Also, are their other spectrum analyzers that are acceptable other than the
ones listed here?
 
http://www.geocities.jp/etm_llc/pub/HP3048A/3048A.html
 
Thanks!  John, K1AE
 
John Allen - PC Support Solutions  
www.pcsupportsolutions.com 
PC On Site Service and Training - Computer HW/SW/Network debugging,
installation and upgrades.  Dell Premier Partner sales.
  Check me out on Yelp!
  mailto:j...@pcsupportsolutions.com M:
508 361-6229
 


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