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
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.
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.
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).