Stable Isotope Geochemistry


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Peter Swart <[log in to unmask]>
Reply To:
Stable Isotope Geochemistry <[log in to unmask]>
Wed, 11 Feb 2004 12:31:55 -0500
text/plain (98 lines)
I am not sure if this is applicable but we have had this happen on our 251
usually after disconnecting cables.  It was a poorly seated connector on
the main data acquisition board.  If you have not done so disconnect and
reconnect all relevant cables.

At 12:32 PM 2/11/2004 -0500, you wrote:
>My Delta Plus is currently in the semi-dreaded no signal in second cup
>state. I know how to get the signal back. Either start a run with no peak
>center, or just restart the software. Either of these will re-initialize
>the hardware and get the signal back. Simply turning the source off and on
>will not get the signal back. However, I'd really rather study the
>situation and try to figure out exactly what is happening, as I have no
>critical samples right now, and this has happened twice within the last 50
>samples I've run. How can I check the actual output from the detectors? The
>detector board stat? What should I even look at?
>Perhaps I should give you some background on my system and what I've done
>and noticed so far.
>My system is a Delta Plus, GPIB interface, installed 2000. I have 5 cups
>(don't ask), 1 and 2 are both narrow and seldom used. My universal cups are
>in positions 3, 4 and 5. Standard wide narrow wide configuration.
>Continuous flow only. Originally had 2 Conflo II's, control selectable by
>an external manual switch. Recently added GasBench/Precon. Initially it was
>a NT 4.0/ISA GBIP system. Currently XP/PCI GBIP ( I know, not supported,
>but seems good so far). I've lost signal in the second cup at the beginning
>of a run with Iso NT 1.2, 1.5, and now 2.0, 4 different software installs,
>2 different computers, 3 different GPIB cards (2 ISA and one PCI) and 3
>different OS installs (NT4 FAT32, NT4 NTFS, and XP). As has been stated by
>Finnigan themselves, this appears to be a MS hardware problem, not software
>or computer/interface hardware. After the last bout of posts on this
>subject and Gilles excellent computer setup procedure, I decided to
>'rebuild' my NT box from the ground up. Seems like it couldn't hurt and if
>he had never seen this problem with all the systems he has I figured it was
>more than worth a try. Maybe there really is some software/computer
>I had many spare parts, so I pulled the original hard drive out of the
>original computer that came with the instrument (Gateway E4200 PIII 450).
>This had REAL/32, NT 4.0 SP 5, and had seen ISODAT 7.5, Iso NT 1.2 and 1.5,
>SP 1.7. It was also FAT 32. Rather than reformat this, I put in another
>hard drive (not new, but compleletly wiped) and started fresh with NT 4.0
>installed with NTFS. This would also allow me to instantly go back to my
>old semi-stable system by simply swapping hard drives if necessary. This
>system was prestine. ONLY Finnigan's software, Isodat NT 1.5, SP 1.8. No MS
>office, no network (while running the instrument), no other applications.
>Even managed to find the correct Intel IDE bus mastering drivers, which
>even Gateway hadn't installed on the original system. Installed EVERY NT
>update (I had to reboot about 20 times to get everything!) as of Nov 2003.
>At the time I only had the original 8-bit ISA GP-IB card, so I used this.
>This system seemed stable, though during the install of my GasBench and
>Precon in Dec, it lost signal in the second cup (cup #4) during a GasBench
>run. Well, this had happened every 500-1000 runs, so I just took it on the
>chin. Then 3 weeks ago during a Conflo/EA sequence it happened again, about
>only 200 runs later. Again, maybe just a fluke, and I really needed to
>finsh, so I restarted the software, reweighed the lost sample and kept going.
>Then this last week I had a chance to try an XP box with a PCI GPIB card
>(National Instruments 2.1 XP drivers) and Isodat 2.0, sp 1.35. Everything
>seemed to be going fairly well. Ran several std on-off sequences, both with
>the GasBench and a Conflo, and had no problems. The I start a regular
>EA/Conflo sequence. On the second sample, the middle cup went dead. I
>stopped the run before it wasted my EA sample, and now that's where I'm at.
>The software returned no errors. This was a nitrogen only run, and I long
>ago abandoned peak centering before every run for nitrogen only sequences.
>If the cup gets 'lost' and you try a peak center, it stops the whole
>sequence with the error peak center not found. If you don't have to peak
>center, the sequence will continue, and you only lose one sample. As I
>said, with the next hardware initialization the signal will come back.
>Oddly, one thing I have encounted is that if I'm doing Carbon only runs,
>the signal tends to be lost after the peak center. The time I lost signal
>with the Gasbench and the next time on the EA I was running carbons, and I
>do peak center for those. I wasn't watching the peak center, but the file
>recorded finding a normal peak center, but then proceded to only acquire
>cups 3 and 5. Every time I've seen this happen with nitrogen, it gets lost
>before the peak center, and the sequence aborts. A clue perhaps?
>Another thing I've noticed is that this is happened more (3 times since
>December) since I added the GasBench and Precon than it has for the last 2
>years with only Conflos. Another clue?
>Anyway, if anyone made it this far, thanks for your attention.
>Howard Sanford
>North Carolina State University
>Dept. of Soil Science
>Box 7619
>3114 Williams Hall
>Raleigh, NC 27695