124 Advanced User Guide
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.
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
Table 25 Agilent data system data processing (continued)
Data rate, Hz Minimum peak
width, minutes
Relative
noise
Detector Column type
Relative noise level
Slower data ratesFaster data rates
Excess noise (due to flow,
oven temperature, detector
block temperatures, etc.)
To Next Page
Loading...
Need help?
General
