[sdiy] [OT] Name that tube

[Alex Stettler]

hi eric,


you aren't right either! ;-)

The pressure isn't messured with the AC-gain.

First the triode type (and the other types like Bayard, Schulz etc.) aren't
operated like a normal triode tube.
The hot filament emitts electrons as usual. But the grid has a positive
potential (120-200 VDC are common).
The outer electrode isn't the anode in this configuration. It's the ion
collector, which is on a lower or slighty negative
potential.

I didn't have looked that up somewhere. I'm operating some of this tubes
(bayard-alpert and a misused EC92) in my own high vacuum system with good
results. And I definitely messure the pressure with the ion current from the
outer collector electrode. Further the whole messuring circuit operates with
stabilized DC voltages, so there aren't a dynamic resistance other any other
dynamic properties involved in the messuring mechanism. ==> no variable AC
gain.

Perhaps the IG35 was one of the first high vacuum gauge tubes which operated
in normal triode configuration.

But I'll bet, that 'IG' stands for Ionization Gauge. So pressure is related
to ion current collected with the outer electrode for sure and definitely
not with AC gain.

alex

-----Original Message-----
From: owner-synth-diy at dropmix.xs4all.nl
[mailto:owner-synth-diy at dropmix.xs4all.nl]On Behalf Of metasonix
Sent: Wednesday, August 13, 2003 5:11 AM
To: synth-diy at dropmix.xs4all.nl
Subject: Re: [sdiy] [OT] Name that tube


>http://www.seanet.com/~tpaddock/public/tube0187a.jpg
>Any idea what this thing is?

Eimac IG35 vacuum gauge.

Just literally a 35T power triode with intubation.

It measures vacuum by the triode's AC gain--the harder
the vacuum, the higher the voltage gain (or, for very high vacuum,
there is an inverted-triode connection that can be a very sensitive
indication of residual gas).

WWII surplus, thus the Navy marking.

Tantalum anode, platinum-plated grid, thoriated tungsten filament,
borosilicate glass.

The green color in the glass around the seals is uranium--it makes
the glass stronger there.

Collectible. Not made in 50 years or more.
About $20 worth of platinum in it. Don't trash it.

>This is a Schulz-Phelps ion gauge tube.
>-closer spaced electrodes than in mostly used Bayard-Alpert ion gauge tube.
>-The collector electrode (the outer, anode-like electrode) has a bigger
surface.
>the Bayard-Alpert gauge tube has only a wire grid around the filament as
collector.
>The Schulz-Phelps type has mostly sheet metal as collector (as could be
seen in the picture)

Nice guess, but wrong! You looked that up somewhere...

ETI still makes all kinds of gauges--Bayard, Schulz, Pirani, triode, etc
etc...
www.etigauges.com/ion12.html

Next?



uncle eric
metasonix.com