Detector Control
Defining Step and Average

The time interval between two recorded data points is referred to as Step.

The smaller the selected step, the more data points will be recorded, thus (generally) ensuring a more precise result. As this increases required storage capacity, Dionex recommends a good compromise between the required information and the capacity.

For intelligent minimization of the required storage capacity, the individual instruments, for example, Dionex detectors, support the setting Step = Auto. However, Dionex recommends that you select a fixed step because an automatic step may result in a faulty integration.

In combination with the Average parameter, the step can optimize the signal-to-noise ratio. See the following example:

Example:  A detector delivers 100 values per channel (A and B) and per second. For channel A, the setting Step = 0.1; Average = On is selected, and for channel B Step = Auto; Average = On.

Channel A:

A step of 0.1 corresponds to a sampling rate of 10 Hz. This means that out of the 100 values that are available, only every tenth value is stored. If the Average signal parameter is On, the values recorded per step are averaged. From 10 values, one average value is formed and is stored. For channel A, 10 signal values per second are stored.

Channel B:

Step = Auto means that the Chromeleon decides depending on events, how many values should be recorded per second. As a different number of values is recorded at different times, a varying number of values is averaged in the final value.

 Tips:

Use Step = Auto for fast test chromatograms for which you do not know the peak width to be expected (method development). For a precise and reproducible analysis, use a fixed step.

For many Dionex detectors, the Data Collection Rate command determines the number of data points collected per second. At the start of data acquisition, the step value is automatically set to the reciprocal value of the selected data collection rate. For some Dionex detectors, only the step value is set, and it is not necessary, or not possible, to set a Data Collection Rate.