Regina,
With the high background voltage on cups 2 and 3, I suspect you're getting air into
the system at some point. It could be the SGE valve on the source housing, but more
likely it's one of the connections in the EA. Have you leak checked your EA? If you
have the 1500 or 2500, you should be able to attach the plug to the gas outlet (which
norally connects to Conflo) and watch the He flow (ml/min) drop to zero. Hit the right
arrow on the EA display to see the He flow rate.
Hope this helps!
-Bill

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Bill Holmes, Research Associate
Terrestrial Ecosystem Laboratory
University of Michigan
School of Natural Resources and Environment
430 East University, Room G540
Ann Arbor, MI 48109-1115
[log in to unmask]   Office:(734)647-0459   Lab: 7-0469/7-0481
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~


----- Original Message -----
From: "Regina Galarza" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Tuesday, November 13, 2001 7:35 AM
Subject: [ISOGEOCHEM] Help


> Dear listmembers,
>
> I need some ideas about what is happening with our Delpta plus. We have a
> Finnigan Delta plus to do continuos flow N2 and CO2 analyses.
> We have problems with the signal in cup 1 (mass. 28 for N2 and mass 44 for
> CO2).
> Three weeks ago; the background signal in all cups was O.K. When the
> reference gas ocurred, the signal in cups 2 and 3 was stable but not in cup
> 1. It had valleys. When we tried to do a stability test, we obtained the
> following delta values:
> delta13/12 for CO2 between 0.18 and 1.81
> delta29/28 for N2 between 0.18 and 0.43.All of them greater than 0.15 per mill
> We thougt that it could be because of contamination in the references gas.
> We changed them and purged the system but the problem persisted.
> At this moment, the background signal in cup 2 and 3 are OK but in cup have
> a value of 14V!!!!!. Is cup 1 break down????? What does it means?
> Any suggestions as to the origin of the problem and a possible solution
> would be greatly appreciated
>
> Thanks                  Regina