Caution:Raw Data Storage
Saving detector signals in digital form is referred to as raw data storage. However, raw data storage also includes other important data, such as the analysis time, signal unit, number of data points, etc.
If a detector is equipped only with an analog output, the data must be converted into digital signals--a task performed by the A/D converter card.
Storage Procedure
With conventional data systems, an analog value is digitized at a fixed time interval and stored with a defined accuracy. The number of values stored per second is referred to as the Sampling Rate. The inverse of the sampling rate (the time interval between two data points) is referred to as the Step.
The higher the sampling rate is (i.e., the smaller the step is), the more data points are stored and the more exactly the original signal can be restored from the stored data. However, a higher sampling rate has higher memory requirements. Therefore, Chromeleon supports the Step=Auto setting. It is true that this setting requires high algorithmic resources in real time, but it provides the following advantages:
Raw data files are as small as possible. Fewer data points would result in a loss of precision. If an analysis requires a conventional step width of 0.5 seconds, Chromeleon can typically acquire such chromatograms with an average step width (= chromatogram length divided by the number of data points) of 2 seconds. Thus, the compression factor is 4:1, making optimum use of the available storage capacity.
Despite the minimal file size, maximum integration accuracy is ensured for the given chromatographic conditions, as the continuous signal is approximated to the optimum. Generally, each peak includes more data points than with conventional acquisition methods.
The processing speed, for example, for peak detection, re-integration, graphical output, etc., is significantly higher due to the reduced number of data points.
Storage Location
Raw data is stored in the directory of the current sequence. Chromeleon creates a separate subdirectory for each channel specified during installation of the program. An Audit Trail directory is created, also. The directories are not visible in the Browser.
The reason is that Chromeleon manages raw data files automatically. Users does not need to access the raw data files directly at any time.
You can view these files in the Windows Explorer, but this is possible only if the datasources are not protected. Besides, the datasource names are not displayed in the Explorer. Therefore, you must follow the path to the corresponding sequence directory.
A separate raw data file is created for each sample in a sequence, for which raw data of a specific channel was recorded.
Caution:
Do not modify these directories! Operations outside Chromeleon are not permitted. Dionex recommends that you protect your datasources to prevent access from the Windows Explorer. In the Browser, select Properties on the context menu or File menu of the datasource and then select the Protect Datasource Directory check box.