Re: [volt-nuts] Traveling Standards
Hello Bob,
LM7815 TC =~ 1 mV/C => 0.125 uA/C => 0.018 ppm/C.
LM7815 line regulation =~ 13 mV/V.
For 35V +/- 10% => 46 mV => 5.7 uA => 0.813 ppm.
I would not heat too much by the voltage regulator.
Or do good thermal isolation.
The covar pins of the hermetic packages have
40uV/K against copper. And Im not shure on my
LTZ1000 if different heating of the LT1763 has
influence. (Distance is only about 1 Inch in the current design).
Rs TC =~ 100 ppm/C => dIs/dT =~ 100 ppm/C => 0.1 uA/C => 0.014 ppm/C.
Rs stability =~ .5% / 1000 hrs => 5.0 uA => 0.714 ppm.
Comments - feedback?
In this case I would use a more stable resistor.
A precision wirewound (NEOHM UPW50 or Riedon USR2) of 10k
in parallel with a 41K2 15ppm 0.1% Metal film (RC55Y).
With best regards
Andreas
Charles P. Steinmetz wrote:
<snip>When one is trying to achieve repeatability in the single-digit ppm
range, I would not leave anything to chance -- and retrace (hysteresis)
is always a matter of chance, particularly if the device has been
powered off for a long time (several days) and may have been exposed to
significant temperature shifts during that time. In my view, the best
approach in this instance is to use something like a 5Ah gel cell (to
ensure relatively little voltage droop during the transit time), with at
least one stage of preregulation. The total package should be under 2
kg and should easily fit into a USPS medium-size flat-rate box that
ships for $11 (this assumes that you and the recipient are both in the
US). UPS should be similar. (If $22 for a round trip is a
deal-breaker, we might conclude that one wasn't very serious about the
project.)
I agree with all of this - but my first objective is to obtain 10 ppm
overall uncertainty. At that level I am hoping that there will be
several folks on the list willing to accept a unit, measure it, and ship
it back to me. Two have already stepped up - thanks!
At 1 ppm I suspect the population of those willing to measure will be
reduced. I know that I certainly could not play in that playground!
Even the well regarded HP3458A only provides that sort of uncertainty
for 24 hours.
You also might include a charger, so that the recipient can top off the
battery before measurement (if necessary) and before return shipment.
Ouch - more weight and more to go wrong.
All measurements would be made with the charger disconnected.
This brings up a good point. I will look for a 24 V DC wall wart to
power the LM7815A. That will remove the transformer from the vicinity
of the reference and should greatly reduce the effect of the line
regulation of the LM7815A. Use of a better 8K resistor would then
eliminate the two largest sources of error (except for the lm199a
itself, of course).
Thanks!
Bob Smither, PhD Circuit Concepts, Inc.
---=======
Firearms stand next in importance to the Constitution itself. They are
the American people's liberty teeth and keystone under independence. The
very atmosphere of firearms everywhere restrains evil interference.
-- George Washington
---=======
Smither@C-C-I.Com http://www.C-C-I.Com 281-331-2744(office) -4616(fax)
In this case I would use a more stable resistor.
A precision wirewound (NEOHM UPW50 or Riedon USR2) of 10k in parallel with a 41K2 15ppm 0.1% Metal film (RC55Y).
Any benefit in switching to a precision current source instead of the resistor? A LT3092, for example, potentially with a LT1634-1.25 reference on the SET pin (as in one of the example circuits in the LT3092 datahseet).
Randy.
In message 4E57F240.8060105@c-c-i.com, Bob Smither writes:
range, I would not leave anything to chance -- and retrace (hysteresis)
is always a matter of chance,
Wouldn't the "degaussing trick" Tektronix uses on the LTZ1000
help here ?
--
Poul-Henning Kamp | UNIX since Zilog Zeus 3.20
phk@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.
In message 4E57DC73.9050804@pacific.net, Brooke Clarke writes:
Batteries are considered hazardous material and can not be shipped
without special Hazmat paper work which complicates things.
Normal Duracell's are perfectly OK, as long as the total stored
energy is less than some non-trivial threshold.
Small VRLA, if built into equipment, are not restricted.
--
Poul-Henning Kamp | UNIX since Zilog Zeus 3.20
phk@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.
Poul-Henning Kamp wrote:
In message4E57F240.8060105@c-c-i.com, Bob Smither writes:
range, I would not leave anything to chance -- and retrace (hysteresis)
is always a matter of chance,
Wouldn't the "degaussing trick" Tektronix uses on the LTZ1000
help here ?
For that to work the chip temperature needs to be cycled.
This is easy to do with an LTZ1000 as the temperature setpoint can
easily be modulated with an external signal.
With an LM399/LM199 cycling the chip temperature ina controlled manner
is more difficult as suitable internal temperaure regulation circuit
nodes arent acessible.
With a discrete zener modulating the chip temperature is easily achieved
via an external heater.
Bruce
Any benefit in switching to a precision current source instead of the
resistor?
Hello Randy,
the only benefit of a current source that I see is that you can use
a lower supply voltage for the whole cirquit.
I use currently 9.35V for the LM399s.
So for me the use of a current source is mandatory.
But with 15V I would not do that.
With a current source instead of using one precision resistor
you will have to use at least two.
And you will have to find out how you can move the "hand adjustment" off
your cirquit with some decoupling capacitors without generating
oscillations.
With the LM399 and a resistor its easy. At the heater I use 100nF directly
at the pins and 47uF not far away. At the output you will have to use 100nF
too.
The resistor will not be sensitive for RF or common mode voltages.
The voltage regulator should be decoupled too at input and output.
With best regards
Andreas
Has anyone tried mounting these 'built in heater' references in a silvered
high vacuum tube for thermal insulation?
It should save a lot of power and so make battery powering easier. In fact
you may have to keep the leads short to stop it overheating just from the
non-heater based dissipation of the reference.
Should sort out any variation due to humidity and atmospheric pressure too.
Scrim
----- Original Message -----
From: "Andreas Jahn" Andreas_-_Jahn@t-online.de
To: "Discussion of precise voltage measurement" volt-nuts@febo.com
Sent: Friday, August 26, 2011 10:33 PM
Subject: Re: [volt-nuts] Traveling Standards
Any benefit in switching to a precision current source instead of the
resistor?
Hello Randy,
the only benefit of a current source that I see is that you can use
a lower supply voltage for the whole cirquit.
I use currently 9.35V for the LM399s.
So for me the use of a current source is mandatory.
But with 15V I would not do that.
With a current source instead of using one precision resistor
you will have to use at least two.
And you will have to find out how you can move the "hand adjustment" off
your cirquit with some decoupling capacitors without generating
oscillations.
With the LM399 and a resistor its easy. At the heater I use 100nF directly
at the pins and 47uF not far away. At the output you will have to use
100nF too.
The resistor will not be sensitive for RF or common mode voltages.
The voltage regulator should be decoupled too at input and output.
With best regards
Andreas
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/ON //Wed Aug 24 02:14:01 UTC 2011/
charles_steinmetz at lavabit.com
mailto:volt-nuts%40febo.com?Subject=Re%3A%20%5Bvolt-nuts%5D%20Looking%20for%20Fluke%20845AB%20manual&In-Reply-To=%3C20110824021410.214CC11BAB5%40karen.lavabit.com%3E/
Wrote:
/
I have a couple of the Artek manuals.I agree they are nice scans,
but I will never buy another one until they quit maxing out the
password security.The ones I have are screwed down so tight you
can't even rotate the pages to look at sideways schematics right-side
up on the monitor.All I care about is the original manual
contents.I don't care about the added features (OCR, bookmarking,
whatever) -- in fact, I'd prefer that they weren't there, so I didn't
have to close the bookmark window every time I opened the
manual.But you can't even use the basic scans as intended because
of the insane security.Anyone who is that paranoid about his
product can keep it.
Charles
As my father likes to say "There are at least two sides to every
story..often more ". So to be fair since you chose to voice your
unhappiness in a public matter please allow me let me share with that
same public forum some other sides to this story
ArtekMediais not a hobby business but a going commercial concern that
pays the mortgage, the light bill and more recently the staggering costs
of my wife's healthcare. We add the copy protection to discourage our
competition from taking our scans and removing various features so that
they can sell them as their own thus depriving us of our income and the
work we put into providing arguably the best after market PDF scans
available. We know this has happened on several occasions as people have
sent us copies of scans they bought from two other PDF manual suppliers
that had our secret mark embedded in them .I was able to prove this fact
and Ebay suspended one of these sellers for 60 days , the other is now
deceased so the point in his case is mute. How these copies came into
the competition's hands we can often only speculate on .
I am not sure what you bought from me in the past but out of over 70,000
PDF's sold in the 10+ year history of the company so far fewer than 2
dozen people have written to complain about the password protection. In
75% of those 2 dozen cases we sent them an unprotected copy . This with
done with the understanding the unprotected copy was solely for their
use and not to be forwarded or extracted from for the benefit of
others. I could not find any record from the last 5 years (searching on
steinmetz and lavabit) and I have no personal recollection of our having
discussed the matter with you in the past as a result of a complaint you
might have voiced as a result of purchasing anything from us. I will
however still reserve for you the benefit of the doubt and If you have
an ArtekMedia scan which you would like unprotected contact me off list
ad we can certainly discuss it further.
Sideways schematics:
99.9% of the time we make an effort to turn all schematics to the
orientation they are meant to be read even if they were originally
printed in 90 degree rotation by the OEM, every now and then one slips
through un-rotated. Adobe Acrobat Pro has an unpleasant habit of auto
rotating things when using the auto page straightening feature. Again if
you havemanual you purchased from us you would like corrected we are
happy to do so , one simply needs to send us an emailat
manuals@artekmedia.com mailto:manuals@artekmedia.comwith the details.
OCR has absolute no affect on manual readability , Upon opening the file
one or two clicks will disable the bookmarking. The help files in Adobe
Reader will explain how to do this if it is not intuitive for you.
In closing Charles we are sorry that you didn't like our service but we
are still happy to correct to whatever level you like those items you
already purchased . To do this a simple and courteous email would gomuch
farther than venting your personal frustrations in a public forum. AS
for my being a "paranoid" . I doubt that you are in professional
capacity to judge my mental state, but if you do have a degree in
psychology or psychiatry than I will withhold my judgment until you can
do further clinical testing to back up your allegation. I do have hard
factual proof that my competition has stolen my copyrighted material ,
and that other well meaning and not so well meaning individuals have
given copies of our scans away. So If I take steps to protect our
material from piracy and that is by your definition "paranoia" ...then
so be it.
As we like to say when I worked for Motorola ..."Paranoia pays ..but the
hours are hell".
Regards
Dave Henderson
President & Founder
Artekmedia
Take a look at the first part (up to ~7:30) of this:
http://www.youtube.com/watch?v=2N6cjGS7lUE
(the rest is interesting stuff, too)
Rob.
Op 26-8-2011 21:27, Randy Scott schreef:
In this case I would use a more stable resistor.
A precision wirewound (NEOHM UPW50 or Riedon USR2) of 10k in parallel with a 41K2 15ppm 0.1% Metal film (RC55Y).
Any benefit in switching to a precision current source instead of the resistor? A LT3092, for example, potentially with a LT1634-1.25 reference on the SET pin (as in one of the example circuits in the LT3092 datahseet).
Randy.
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