Re: Bombing -TC gauge recalibration

To: neon-l@netcom.com
Subject: Re: Bombing -TC gauge recalibration
From: marcus@ttphysik.uni-duisburg.de
Date: Thu, 28 Mar 1996 12:45:17 +0100 (MESZ)
In-Reply-To: <v01530502ad7cc786cb70@[153.37.8.207]> from "Tom U." at Mar 25, 96 07:17:03 pm
Reply-To: neon-l@netcom.com
Sender: owner-neon-l@netcom.com

You shouldn't wonder about your wrong gauge reading.
All TC / Pirani gauges are VERY temperature dependent, the linearization
is always not correct.
They contain a very thin platinum filament (5 micron diameter) which
very easy bcomes contaminated by pump oil and/or mercury condensing. 
Some gauges have the possibility to heat up the filament for cleaning. 

But every TC needs a recalibration of zero pressure ( best vacuum 
a good trapped diffusion pump can give) and of atmosphere as
second point. easy to do if you have two marks on your scale. 
You should do this every three or four months, depending on 
how clean your pump and manifold are. 
Avoid straight connection of the gauge to the tubulation connector
on the manifold, so in case of tube breakage or vacuum breakdown 
nothing can rush into the gauge and contaminate the filament. 
Just insert a right angle bend. 
(In our lab, we recal our TC gauges once a month or so.)

Marcus Thielen
Student of physics at Duisburg University
marcus@ttphysik.uni-duisburg.de

References:

Bombing advice helped!

From: neonthom@earthlink.net (Tom U.)