Richard Moore | 24 May 06:32 2015
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Guildline Standard Resistors -- Oil bath temp?

Anyone know what temperature Guildline used for the oil bath of the precision resistance standards?
Four Designs Company | 23 May 18:57 2015
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Re: volt-nuts Digest, Vol 69, Issue 19, Datron 1281 offset null, bias current adjustment

The offset adjustment R317, is an AC adjustment, not DC as one might 
surmise. As I recall I applied a 10X scope probe to the  O/P point at 
the junction of R329 and R330 to view the AC component. I probably used 
a 10Meg ohm with a cap in parallel, in a well shielded enclosure across 
the input jacks. I probably set the 1281 to the 10V range.

As for R222 the input bias, I think I just barely touched up the 
adjustment so that there was little drift with the input open. That is, 
the input would float around a low displayed value, and climb to a large 
number in either polarity.

I paraphrased the adjustment info from the 1081 and applied it as much 
as possible to the 1281.

Another thing I learned from owning two, and working on a few more 
1281's is that the first thing to do is replace all the aluminum 
electrolytic caps on the analog board as a minimum. Especially the small 
1uf caps on the 3-terminal regulators die and the noise increases. This 
will cause all kinds of problems. I change them all, on all the boards. 
Due to the low profile of the larger caps careful selection is necessary.

A few years ago I had email contact with one of the technicians at Fluke 
Farnborough, the home of the 1281. He wasn't much help, but
indicated that internal adjustment procedures were never released. He 
wouldn't provide any details either..

Sorry for the nebulous response, but it has been awhile since I adjusted 
mine.

Bob Koller
(Continue reading)

starbook | 23 May 10:39 2015
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Datron 1281 offset null, Bias current adjustments


I have a Datron 1281 DMM.
How to set the bias current adjustment (R222)?
How to set the offset null adjustment (R317)?
Thanks,
John Staron
starbook | 23 May 10:38 2015
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Datron 1281 offset null, Bias current adjustments


I have a Datron 1281 DMM.
How to set the bias current adjustment (R222)?
How to set the offset null adjustment (R317)?
Thanks,
John Staron
frank.stellmach | 22 May 08:54 2015
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3458A resistance calibration

Dear Anton,
 
Vishay developped the C foil resistors in 1962, having a "negative" parabola with +/- 2ppm/K T.C.
In 1982 the K-foil was introduced, having a "positive" parabola, +/-1ppm/K T.C.
 
Both were still available, types S102C, and S102K, respectively.
 
The Z foil was introduced in 2002.
 
Therefore, when the HP3458A was designed, the K-foil resistor was used, in a hermetic package.
This was probably the original component, as found in the BOM of the CLIP (1.3ppm/K), and also
manifested in the still valid specification of the 3458A, i.e. 1ppm/K, 10ppm/year.
 
 
The VHP101 was already available in the 1990ties, the T.C. probably specified to  <=0.5ppm/K at that time.
HP obviously switched to that more stable type about 10 years later.
 
Inside the actual VHP101, (since about 2005, or so), there were two chips in series connection, one C-foil,
and one K-foil, so that the total T.C. is cancelled to an average T.C of 0.3ppm/K.
 
Frank
 
 
 
Dear Frank,
Could You give me more detail which resistor has C-foil and which K-foil.
Anton

---
Alle Postfächer an einem Ort. Jetzt wechseln und E-Mail-Adresse mitnehmen! Rundum glücklich mit freenetMail
(Continue reading)

Frank Stellmach | 22 May 00:32 2015
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3458A resistance calibration

Re To: *Electronics and Books

Dear Frans,

I cant't believe this! Thanks alot!

As you mentioned the VHP101 as a reference resistor in your'98 unit, I 
just opened my HP3458A from 2000, and it's also a VHP101!

According to the actual Vishay PG datasheet, it's really the best type 
they offer currently.
As I learnt from a Vishay representative years ago, they pair two 
resistor elements inside, i.e. a C-foil, and a K-foil, to compensate for 
the T.C.

The VHP101 has 10ppm absolute/max. variation over 15..45°C, i.e. an 
average of 0.3ppm/K, and it's oil filled, giving  2ppm/6year stability.
Both parameters I really can believe in, (I'm otherwise very sceptical 
about Vishays specs) as these are specified as being max. value by this 
window definition, and the annual stability of oil filled, hermetically 
sealed Vishay types, I have checked on 5 EA VHP202Z over > 5 years, 
meanwhile.

I was not aware of this ultra stable reference resistor inside my 
instrument, as the 40k resistor in my unit was bent backwards, so I 
could not read the type designator, and did not dare to touch it, up to now!

The old CLIP specifies this resistor as having 1.3ppm/K, so I always 
assumed a Vishay k-foil of the 1989 era, non oil filled type.
Also the datsheet specified 1ppm/K (selected component), and 10ppm/year, 
(Continue reading)

easy 3458A AC calibration

It is stated that the ac calibration of a 3458 is so difficult. at least the equipment mentioned is so
difficult to obtain. but look what you need. a hp signal generator 3325 where i have a pile of (any other good
generator will do to), an other hp 3458 and 3 different thermocouples. very expensive nowhere to be found
and very delicate. hp not procduced them for 40 years or ballantine which cost more then the meter your calibrating.
but now for the accuracy. the signal generator has only 3 digits of amplitude resolution. if you see the
accuracy in the hp protocol what to measure it is not possible to generate that.
and for the thermocouples. they give only millivolts. you need an other 3458 with no offset or better a
nanovolt meter to measure them.
a far easier solution is a hp powersensor 8482a on a hp power meter. it is a thermocouple of the correct
frequency range and can be measured accurate enough for the generator.
the ac calibation is not an exact value as the volt or resistor but only a deviation in the frequency range. it
is even difficult to obtain the deviation in 3 digits.
ok it took me an hour but then i was done.

Regards

Frans

info@...
Netherlands

Discere ne cesses

3458A resistance calibration

my 3458 was getting troubles with the calibration of the zero. As volts where no problem and ohm were pretty
accurate, my conclusion was that there is basicly nothing wrong. the calibration stopped at the ohm-10.
so it must be in the sense lines somewhere. on de dc print there where 2 big resistors (Dale ?) in the sense
lines. with a magnifying glass i could spot litle cracks in the solder. after heating with some fresh
solder the fault was over.

i have red several times that the standard resistor for ohms should be of a better type. In my 1998 production
unit it is a vishay vhp101 40k. that must be one of the better ones that were made by vishay. in an older 1994
unit there was no brand or recognisable type code on it.

Regards

Frans

info@...
Netherlands

Discere ne cesses
wb6bnq | 18 May 23:29 2015
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Re: HP 735A DC Transfer Standard

Hi Roy,

I hate to tell you but the hp-735 does not compare to the Fluke 731.  
The hp-735 had a drift that was constant.  This information came from a 
friend of mine that was responsible for the US Navy's Primary DC voltage 
standard at their Primary Lab in San Diego, CA in the 1970's.  The 
actual drift rate I do not recall anymore, but it was significantly 
higher than the any drift in the Fluke.

Bill....WB6BNQ

R.Phillips wrote:

>
>
> -----Original Message----- From: gilbenl@...
> Sent: Sunday, May 17, 2015 4:13 AM
> To: volt-nuts@...
> Subject: [volt-nuts] HP 735A DC Transfer Standard
>
> Recently acquired a HP 735A DC Transfer Standard. Replaced some caps, 
> but its otherwise clean and has since been powered. Read a post 
> recently about a 735A oven failure that included a teardown that 
> revealed why HP states the oven/ref assembly a non-serviceable part. 
> The failure in this person's device was the heater, specifically the 
> thermistor.
>
> Anyone on this board have a 735A in use? Do you keep it powered 24/7 
> or as-needed? Any failures/repairs/mods?
>
(Continue reading)

Marv @ Home | 18 May 14:03 2015
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Re: "*WAY* too expensive for even Keysight to redesign"

FYI, when a US patent expires the product is no longer patented and 
the maker cannot use the term patented, or its number, in products or 
literature.
Pequignot v. Solo Cup, 09-1547, June 2010, the Federal Circuit 
confirmed that "articles marked with expired patent numbers are 
falsely marked."   The case also discusses the use of the term patented.

Speaking of the 34401a, it was extensively redesigned as the 34461a 
and a few variants of it.  You can use it as a case study of what 
needs to be done to redesign a defacto standard.

At 07:02 PM 5/17/2015, wrote:
>"I would think that a lot of the patents would be running out soon as if
>that would make any difference."
>
>Here are some patents related to the HP3458A.
>It looks like all of these patents have expired.
>A new instrument based on these concepts and schematics can be marked,
>"Protected by the following Patents".
>US4357600
>US4951053
>US5148171
>US5689260
>etc ...
>
>
>I do not own a HP3458A, but I admire the instrument and the people that
>made it.
>The best meter I own is a HP34401A.
>It is good enough for the measurements I usually make.
(Continue reading)

Ivan Cousins | 18 May 01:02 2015
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"*WAY* too expensive for even Keysight to redesign"

John Phillips wrote:
"I would think that a lot of the patents would be running out soon as if
that would make any difference."

I think that John Phillips is right.

Here are some patents related to the HP3458A.
It looks like all of these patents have expired.
A new instrument based on these concepts and schematics can be marked,
"Protected by the following Patents".
US4357600
US4951053
US5148171
US5689260
etc ...

I do not own a HP3458A, but I admire the instrument and the people that
made it.
The best meter I own is a HP34401A.
It is good enough for the measurements I usually make.

Ivan Cousins
A time-nut since before 1974,
the year I started working at Tektronix.

Gmane