234 Advanced Operation Manual
7 GC Output Signals
You cannot change the data rate during a run.
You will see higher relative noise at the faster sampling
rates. Doubling the data rate can double peak height while
the relative noise increases by 40%. Although noise increases,
the signal- to- noise ratio is better at the faster rates.
This benefit only occurs if the original rate was too low,
leading to peak broadening and reduced resolution. We
suggest that rates be chosen so that the product of data rate
and peak width in seconds is about 10 to 20.
The figure shows the relationship between relative noise and
data rates. Noise decreases as the data rate decreases until
you get to data rates of around 5 Hz. As the sampling rate
slows, other factors such as thermal noise increase noise
levels.
10 0.02 0.7
5 0.04 0.5 to
2 0.1 0.3 All types
1 0.2 0.22
0.5 0.4 0.16
0.2 1.0 0.10
0.1 2.0 0.07 Slow packed
Tabl e 58 EZChrom/ChemStation data processing (continued)
Data rate, Hz Minimum peak
width, minutes
Relative
noise
Detector Column type
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