Data Acquisition for more information).Data Collection Rate
The rate at which Chromeleon collects digital data points from the detector, expressed as points per second or Hertz (Hz), is referred to as the data collection rate. The data collection rate of detectors corresponds to the Sampling Rate of A/D converters (refer to Data Management Data Acquisition for more information).
In general, each peak should be defined by at least 20 data points. For chromatograms with co-eluting peaks or low peak-to-noise ratios, 40 points per peak are better.
If you expect all of the peaks to be relatively wide, use a slow data collection rate.
If any peaks of interest are less than a few seconds wide, set a fast data collection rate.
If the data collection rate is too slow, the peak start and end will not be precisely determined. If the data collection rate is too fast, data files will occupy more disk space and take longer than necessary to process.
Step vs. Data Collection Rate
In addition to the data collection rate, a step value is set. The step value is the reciprocal value of the selected data collection rate. For example, if you select a data collection rate of 5 Hz, the step value is automatically set to 0.2 second at the start of data acquisition. In general, Dionex recommends using the automatically selected step value (see Step for exceptions). It is possible to specify a step value that is independent of the data collection rate; however, only advanced users should do this. Refer to the detector operator's manual for guidelines.
Tip:
When you issue the Data Collection Rate command, the Step value is automatically set to the reciprocal value. Therefore, if you want to use a different step value, place the Step command after the Data Collection Rate command in the program.
Setting the Data Collection Rate for Integrated Amperometry Data
For 2D integrated amperometry data, the data collection rate is governed by the Waveform period. Chromeleon generates one integrated data point per waveform period. The data collection rate determines the rate at which this data is stored. The data collection rate is usually equal to the reciprocal of the waveform period. Thus, every integrated data point is stored. It is also possible to set the data collection rate to less than the reciprocal of the waveform:
data collection rate £ 1/waveform period
Note:
The data collection rate does not apply to 3D amperometry data. 3D data is collected at a fixed rate of 1 kHz.