3 • Operation and Maintenance
Doc. 031644-02 9/03
3-17
Data Collection Rate
The data collection rate (or
sample rate
) is the number of data points per second
(Hz) at which the host computer stores data from the PDA-100. (The detector
electronics always collect data at 10.0 Hz.)
The data collection rate can be set to 0.25, 0.5, 1.0, 2.0, 2.5 (default), 5.0, or
10.0 Hz. The maximum number of data points is stored at 10.0 Hz. Slower data
collection rates store the average of the 10.0 Hz points; for example, a 2.5 Hz rate
stores the average of four 10.0 Hz points.
•
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 (1.0 Hz, for
example).
•
If any peaks of interest are less than a few seconds, select a faster data
collection rate (5.0 Hz, for example).
•
If the data collection rate is too slow, the start and end points of peaks are not
accurately determined. However, 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.
•
The table below lists the recommended pairings for the rise time and data
collection rate.
Rise Time
(seconds)
Data Collection Rate
(Hz)
0.1
10.0
0.2
10.0
0.5
5.0
1.0
2.5
2.0
2.0
5.0
0.5
