AT Voltmeter

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I picked this gizmo up at the local junque shoppe. Pics on a.b.s.e. It  
appears to be an r.f. tuned cavity. Any info or comments?

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Paul Hovnanian     mailto: snipped-for-privacy@Hovnanian.com
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Re: AT Voltmeter
On Thu, 06 Oct 2016 21:25:59 -0700, "Paul Hovnanian P.E."

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Sensitive Research Instrument Corp (Singer Metrics or Singer Gertch)
made mostly electrostatic voltmeters.  I couldn't find anything
Sensitive Instruments made that might be RF related.  I have no clue
what an "AT Voltmeter" might be.  The Ballantine 390 is listed as an
"A-T Voltmeter" but I don't want to download 38MBytes just to see the
catalog.

This looks like the Ballantine version of the same cavity:
<http://www.surplussales.com/EQUIPMENT/TESTEQUIPMENT/TESTEQUIP-19.HTML
Kinda looks like the micrometer adjusts a big piston capacitor, and
not a RF cavity, but I'm gussing.

I don't think that glass device is an acorn tube.  Not tall enough,
not enough leads, no filament, and not enough external connections. My
guess(tm) would be either a spark gap or a neon lamp protector.
There's a number on the bottom of the glass envelope, which might
help.  

Value?  No clue.
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Jeff Liebermann     snipped-for-privacy@cruzio.com
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Re: AT Voltmeter
wrote:


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More of the same:
<http://www.surplussales.com/equipment/Close-ups/eqp-bal-390_L.html

Still no clue on what it does.  The wooden box makes me think it's
part of some test setup.  The labels on the connectors in the photo
would have been helpful.

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Jeff Liebermann     snipped-for-privacy@cruzio.com
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Re: AT Voltmeter
Jeff Liebermann wrote:

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This exactly wht it is. The make/model number lead to this page:

http://lcweb2.loc.gov/master/mbrs/recording_preservation/manuals/Ballatine%20A-
T%20Voltmeter%20Model%20390.pdf

and this is what I've got. The little 'acorn tube' is a glass encapsulated  
thermocouple. It even says '5 mA' on it.

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The little 'acorn tube' is a glass encapsulated thermocouple. It even says  
'5 mA' on it.
  
Thanks!

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Paul Hovnanian     mailto: snipped-for-privacy@Hovnanian.com
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Re: AT Voltmeter
More info: The Ballentine Model number lead me to this description:

"Attenuator-thermoelectric highfrequency voltmeter" and patent:

https://www.google.com/patents/US2933684

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Re: AT Voltmeter
On Fri, 07 Oct 2016 15:59:15 -0700, "Paul Hovnanian P.E."

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Nice.  It's all in the patent.  Apply some RF to one end of the tube.
The micrometer controls the capacitive coupling to the thermocouple,
which produces enough voltage to move a millivoltmeter.  I guess today
it would be called a thermal RF power meter or bolometer.  The big
advantage is that it stays calibrated longer than other schemes of its
day (1956).

I have no clue what you might be able to do with it.  Rip out the
thermocouple and you have a rather precise adjustable capacitor.  You
might try selling it to someone with a calibration lab or museum of
antique secondary calibration instruments.

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Jeff Liebermann     snipped-for-privacy@cruzio.com
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Re: AT Voltmeter
Jeff Liebermann wrote:
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    The link below is to the website of a deceased friend who  collected  
antique electronics. About 2/3 down the page are a number of their early  
thermocouple based meters, along with a little of the history of  
Sensitive Research. I have one of the 'Polyranger' meters that he mentions.

    Randy Guttery was a US Navy Veteran, and a Broadcast engineer in  
Meridian Mississippi. He was an excellent electronics tech, as well.

http://www.comcents.com/te.php

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Re: AT Voltmeter
On Thu, 27 Oct 2016 17:14:59 -0400, "Michael A. Terrell"

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Thanks.  Of the test equipment shown, I think I have either used,
owned, or still own much of it.  If ever get tired of the stuff, I'll
open a museum.  I've seen some Sensitive Research stuff at various
times, but was never into calibration or metrology, so they were of
little interest.  Thanks much.



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Jeff Liebermann     snipped-for-privacy@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
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Re: AT Voltmeter
The inventors were employees of US National Bureau of Standards and wrote a  
paper on their invention:

http://nvlpubs.nist.gov/nistpubs/jres/44/jresv44n1p15_A1b.pdf


Re: AT Voltmeter
Thanks to you and Jeff for the links. I think I've got enough to figure this  
beast out.

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Paul Hovnanian     mailto: snipped-for-privacy@Hovnanian.com
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Re: AT Voltmeter
Jeff Liebermann wrote:
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    You're welcome. I did some work in a Metrology lab, while at  
Microdyne. My latest addition to my home shop is a Boonton 9200A digital  
RF Milivoltmter. It will replace the analog 92B model that I've had for  
decades. It's too bad that it doesn't have the second channel, or  
IEEE-488 interface.

The S-R Polyranger had been donated to a Vocational Electronics course.  
It was given to me, when the school system dropped the course. I was on  
the Board of Advisers for that course.

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They don't get mad.

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