Dual ECD Signal & A/D box problem

Chromatography Forum: GC Archives: Dual ECD Signal & A/D box problem
Top of pagePrevious messageNext messageBottom of pageLink to this message  By Randy Bower on Monday, December 8, 2003 - 08:23 am:

Hello,

I'm trying to perform an analysis using very short (6m) megabore columns (0.53mm) into dual ECDs. The problem I am having is that the A/D box won't accept a signal below a certain point, and the trace is being cut off in the middle of the run. There's just a flat line until a peak gives enough signal for the A/D box to recognize. I'm not sure how to fix this.

Equipment is a Varian 3400 GC and Turbochrom 4.1.2 software with Perkin-Elmer 900 A/D interface.

TIA for any advice


Top of pagePrevious messageNext messageBottom of pageLink to this message  By Anonymous on Monday, December 8, 2003 - 08:52 am:

Sounds like the zero is set above the signal. Try setting the zero well below the signal.


Top of pagePrevious messageNext messageBottom of pageLink to this message  By Randy Bower on Monday, December 8, 2003 - 10:32 am:

That's what I thought. There's only one place in the software to set the range: if you are familiar with the TC software, then it's in the Real-time Plot section. I set it to -50 for the zero, but that still results in a flat line at the 0 mV mark.


Top of pagePrevious messageNext messageBottom of pageLink to this message  By Anonymous on Tuesday, December 9, 2003 - 02:08 am:

The PE Nelson boxes can't accept a negative signal. You need to program an offset at the GC, such that the baseline gives a postive reading (e.g. 10 mV).


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