Instrument Type:
Detector
Type:
Fixed point value
Value Range:
Depends on the channel; for example, for a UV channel: 0.01 ... 4.80 [s] or Auto
Note:
When using Auto, you may receive minor inconsistencies in the last few data points of the signal. This is expected and does not affect the chromatographic results.
Default:
Depends on the detector and the channel
Related Commands:
Description:
The Step determines the time interval between two consecutive data points within the signal's raw data file. In combination with the Average parameter, the signal-to-noise-ratio can be optimized.
Tip:
For most Dionex/Thermo Scientific detectors, you can define the number of data points measured per second using the Data Collection Rate command. In this case, Chromeleon automatically determines the Step value as the reciprocal value of the Data Collection Rate. Only advanced users should modify this value. In this case, you must issue the Step command after the Data Collection Rate command.
Function:
You can select a fixed step value or a variable step (Auto).
Usually, select a fixed step. This is required in particular if you want to export the recorded raw data to external software applications that can only process equidistant data points.
Use the Auto step for fast test chromatograms for which you do not know the width of the expected peaks (method development). For a precise and reproducible analysis, always use a fixed step (see below). Especially with increased baseline noise, using Auto may result in incorrect integration.
Fixed Step [0.01 .... 4.80 s]
Every step seconds, a data point is stored in the raw data file. For example, step = 0.5 means that 2 data points are acquired and stored per second. The smaller the step, the more data points will be recorded per time unit (regardless of whether there is a baseline segment or a peak).
For detectors that have no data collection rate setting, Step (here, 0.1 - 4.0 s) defines the data rate at which the connected Photodiode Array Detector collects spectra for the 3D field.
Tip:
Select the step in such a way that 20 data points are placed on the narrowest relevant peak of your chromatogram. If you acquire more data points, this will use unnecessary disk space, and the integration may become incorrect, especially with increased baseline noise.
Variable Step [Auto]
Depending on whether the peaks are narrow or wide, or a baseline segment is recorded, Chromeleon stores 0.2 to 100 data points per second as the result. Thus, the step automatically varies between 0.01 and 5 seconds. For 2D channels, use the MaxAutoStep command to define the maximum step for Auto.
Note:
To display the raw data points selected by Chromeleon in the Report, click Decoration on the context menu. On the Peak Decoration tab page select the Raw Data Point check box.
