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WarrenS

Thu, Sep 8, 2011 11:00 PM

Bob

Another thought.
Soldering plastic voltage reference parts to a PCB can also cause stress
problems.
Part of your high resolution testing should be to Flex the PCB board a
little in both axes.
Then push and tap on the top the parts a little to see what happens.
I've seen some parts work better as a strain gain than a voltage reference
when mounted to a PCB.

ws

Hello Bob,

one thougth of me just seeing the pictures.
how is the "top" and "bottom" of LM399 stabilized with your tube package.

Even when top and bottom is defined. The tube can be tilted by around 45 to
90 degrees.
Did you check if that has an influence on the output voltage?
Is the PCB fixed within the tube?

Thanks Fred. Both references (the LM119AH and the MAX6350) have several
hundred hours on them. I have left them on for all the time since I put
together the first bread board. When I was not working on them, they have
been powered. They will accumulate an additional hundred hours or so
before I actually ship them.

At least the plastic case of the MAX6350 will have suffered from soldering.
(dryed out).
So it will take at least a week or two until the unit has again stabilized.

With best regards

Andreas

----- Original Message -----
From: "Bob Smither" <smither at c-c-i.com>
To: "Discussion of precise voltage measurement" <volt-nuts at febo.com>
Sent: Tuesday, September 06, 2011 7:04 PM
Subject: Re: [volt-nuts] Traveling Standards - pictures

I finally found time to post some pictures of the TS:

http://c-c-i.com/image/tid/2

--
Bob Smither, PhD Circuit Concepts, Inc.

---=====

Bob Another thought. Soldering plastic voltage reference parts to a PCB can also cause stress problems. Part of your high resolution testing should be to Flex the PCB board a little in both axes. Then push and tap on the top the parts a little to see what happens. I've seen some parts work better as a strain gain than a voltage reference when mounted to a PCB. ws **************** Hello Bob, one thougth of me just seeing the pictures. how is the "top" and "bottom" of LM399 stabilized with your tube package. Even when top and bottom is defined. The tube can be tilted by around 45 to 90 degrees. Did you check if that has an influence on the output voltage? Is the PCB fixed within the tube? > Thanks Fred. Both references (the LM119AH and the MAX6350) have several > hundred hours on them. I have left them on for all the time since I put > together the first bread board. When I was not working on them, they have > been powered. They will accumulate an additional hundred hours or so > before I actually ship them. At least the plastic case of the MAX6350 will have suffered from soldering. (dryed out). So it will take at least a week or two until the unit has again stabilized. With best regards Andreas ----- Original Message ----- From: "Bob Smither" <smither at c-c-i.com> To: "Discussion of precise voltage measurement" <volt-nuts at febo.com> Sent: Tuesday, September 06, 2011 7:04 PM Subject: Re: [volt-nuts] Traveling Standards - pictures >I finally found time to post some pictures of the TS: > > http://c-c-i.com/image/tid/2 > > -- > Bob Smither, PhD Circuit Concepts, Inc. > =======================================================================

BS

Bob Smither

Fri, Sep 9, 2011 1:19 AM

WarrenS wrote:

Bob

Another thought.
Soldering plastic voltage reference parts to a PCB can also cause stress
problems.
Part of your high resolution testing should be to Flex the PCB board a
little in both axes.
Then push and tap on the top the parts a little to see what happens.
I've seen some parts work better as a strain gain than a voltage
reference when mounted to a PCB.

Good suggestion. I will include that when I get the differential test
setup.

Best regards,

Bob Smither

WarrenS wrote: > Bob > > Another thought. > Soldering plastic voltage reference parts to a PCB can also cause stress > problems. > Part of your high resolution testing should be to Flex the PCB board a > little in both axes. > Then push and tap on the top the parts a little to see what happens. > I've seen some parts work better as a strain gain than a voltage > reference when mounted to a PCB. Good suggestion. I will include that when I get the differential test setup. Best regards, Bob Smither

AJ

Andreas Jahn

Fri, Sep 9, 2011 5:26 AM

WarrenS wrote:

Bob

Another thought.
Soldering plastic voltage reference parts to a PCB can also cause stress
problems.
Part of your high resolution testing should be to Flex the PCB board a
little in both axes.
Then push and tap on the top the parts a little to see what happens.
I've seen some parts work better as a strain gain than a voltage
reference when mounted to a PCB.

Good suggestion. I will include that when I get the differential test
setup.

Yes really good point. Just yesterday I did the first tests on my
new built reference VRE3050AS (#1). It is claimed to be the
most stable non heated reference according to the manufacturer.
Because of the hermetic ceramic package I thougth that I can
solder it directly to the PCB. But I had around 180 uV difference
from max to min by tweaking the PCB. Which is less than the
values found from other references, but which is much more
than my 5uV value when soldering only the ground pin directly
to the PCB.

With best regards

Andreas

> WarrenS wrote: >> Bob >> >> Another thought. >> Soldering plastic voltage reference parts to a PCB can also cause stress >> problems. >> Part of your high resolution testing should be to Flex the PCB board a >> little in both axes. >> Then push and tap on the top the parts a little to see what happens. >> I've seen some parts work better as a strain gain than a voltage >> reference when mounted to a PCB. > > Good suggestion. I will include that when I get the differential test > setup. Yes really good point. Just yesterday I did the first tests on my new built reference VRE3050AS (#1). It is claimed to be the most stable non heated reference according to the manufacturer. Because of the hermetic ceramic package I thougth that I can solder it directly to the PCB. But I had around 180 uV difference from max to min by tweaking the PCB. Which is less than the values found from other references, but which is much more than my 5uV value when soldering only the ground pin directly to the PCB. With best regards Andreas

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Re: [volt-nuts] Traveling Standards - pictures + protocol