Thermo Scientific 074114, Operator'S Manual

Page: 53 / 148

3 • Operation and Maintenance
Doc. 065378-01 1/12
45
Data Collection Rate
The data collection rate (or sample rate ) is the number of data points per second
(Hz) at which the computer stores data from the Dionex PDA. (The detector
electronics collect data at up to 20.0 Hz.)
The Dionex PDA data collection rate settings are 0.25, 0.5, 1.0, 2.0, 2.5 (default),
5.0, 10.0, or 20.0 Hz. The maximum number of data points is stored at 20.0 Hz.
•
In general, each peak should be defined by at least 20 data points. For
chromatograms with co-eluting peaks or low signal-to-noise ratios, 40 data
points per peak is recommended.
•
If all peaks are relatively wide, select a slower data collection rate (for
example, 1.0 Hz).
•
If any peaks of interest are less than a few seconds, select a faster data
collection rate (for example, 5.0 Hz).
•
If the data collection rate is too slow, the start and end points of peaks are not
accurately determined. If the collection rate is too fast, data files may occupy
excessive disk space and post-run analyses may require more processing time.
•
A slow data collection rate with a fast rise time may result in a longer system
response than indicated by the rise time. For example, a data collection rate of
0.5 Hz and a rise time of 0.5 second results in a system response longer than
2.0 seconds.
•
At a data collection rate of 20 Hz, the 3D sample wavelength range must be
d
310 nm. Regardless of the data collection rate, the reference wavelength (if
set) must always be within the 3D range.
•
These are the recommended pairings for the rise time and data collection rate:
Rise Time
(seconds) Data Collection Rate
(Hz)
0.05 20.0
0.1 20.0
0.2 10.0
0.5 5.0
1.0 2.0
2.0 1.0
5.0 0.5