AT Voltmeter

[Paul Hovnanian P.E.]

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?

[Jeff Liebermann]

On Thu, 06 Oct 2016 21:25:59 -0700, "Paul Hovnanian P.E."

Post by Paul Hovnanian P.E.
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?

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.

[Jeff Liebermann]

Post by Jeff Liebermann
<http://www.surplussales.com/EQUIPMENT/TESTEQUIPMENT/TESTEQUIP-19.HTML>

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.

[Paul Hovnanian P.E.]

Post by Jeff Liebermann
On Thu, 06 Oct 2016 21:25:59 -0700, "Paul Hovnanian P.E."

Post by Paul Hovnanian P.E.
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?

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.
<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.

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.

Post by Jeff Liebermann
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.

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

Thanks!

[Paul Hovnanian P.E.]

More info: The Ballentine Model number lead me to this description:

"Attenuator-thermoelectric highfrequency voltmeter" and patent:

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

[Jeff Liebermann]

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

Post by Paul Hovnanian P.E.
https://www.google.com/patents/US2933684

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.

[Michael A. Terrell]

Post by Jeff Liebermann
On Thu, 06 Oct 2016 21:25:59 -0700, "Paul Hovnanian P.E."

Post by Paul Hovnanian P.E.
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?

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.
<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.

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

[Jeff Liebermann]

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

Post by Michael A. Terrell
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

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.

[DaveC]

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

[Paul Hovnanian P.E.]

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

[Michael A. Terrell]

Post by Jeff Liebermann
On Thu, 27 Oct 2016 17:14:59 -0400, "Michael A. Terrell"

Post by Michael A. Terrell
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

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.

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.

[Tom Biasi]

Just picked this gadget up at the local junque store. Apears to be an r.f.
tuned cavity. It has a acorn tube inside with marking "5 mA" that I can't
identify. Any info or ideas as to what this might be worth? If nothing, at
least it has a nice barrel micrometer on the end that I can put to use.

Tucker has a manual for it for 20 bucks.
http://www.etestmanuals.com/Search.aspx?Mfg=SRI

[Paul Hovnanian P.E.]

Post by Tom Biasi
Tucker has a manual for it for 20 bucks.
http://www.etestmanuals.com/Search.aspx?Mfg=SRI

I saw that. But it's more than I paid for the gadget.