The Data Channels command in the Instrument menu controls how TotalChrom acquires analog and digital data by letting you set the channel or channels for data collection, the data sampling rate, and the analysis run time. The options available on the Data Channels tab depend on the type of instrument that you are using.
¾ To set channel options for a LINK-controlled instrument:
1. Choose Data Channels from the Instrument menu to open the Data Acquisition dialog box with the Data Channels tab selected.
Series 200 DAD: The Data Channels dialog has a slightly different configuration for a Series 200 DAD detector, but the name and function of the available controls is the same as those described in this procedure.
Series 200 UV/VIS: The Data Acquisition dialog screen for the Series 200 UV/VIS uses the standard LINK instrument layout. Since only a single channel is available with the Series 200 UV/VIS, Channel A is always selected and Channel B and the Dual radio buttons are disabled. The Source setting will always be Series 200 UV/VIS (the only selection available).
2. Under Data Channel, select channel A, B, or Dual.
3. Under Source, select a data source for one or both channels from the list of choices supported by this instrument.
4. Under Set Data Rate, do one of the following to set the rate at which the instrument will sample its detectors:
• Select By Peak Width At Base, and then enter the number of seconds in the text box.
• With this option, TotalChrom acquires data in terms of the width (at its base) of the narrowest peak that you expect to occur in the run. If you enter a peak width, TotalChrom calculates the optimum sampling rate for that peak width, collecting at least 20 data points across the peak. • Select By Sampling Rate, and then enter or select a rate.
With this option, TotalChrom acquires data from the instrument using the number of data points per second that you explicitly set (or the nearest available rate to that value).
5. Under Data Storage, do one of the following:
• Select Store All Data From Run to store all the data from a run. TotalChrom collects and stores data for a run based on your instrument conditions. This option is useful if you don't know the run time because you haven't entered the GC oven program or LC solvent program. • Deselect Store All Data From Run to store only the data collected in a
given time window.
You must specify the relevant times. In the Delay Time text box, enter the number of minutes that you want to elapse between the start of the run and when data analysis starts. A value entered here does not affect the measurement of peak retention time. In the Run Time text box enter the number of minutes for which you want the interface to collect data. Note that TotalChrom will not allow the delay time to be greater than the run time.
The number of data points value is calculated as follows:
Data Points = RT x SR x 60
where RT is the run time and SR is the sampling rate.
6. If your instrument supports the uploading of run logs, you can select Store Run Log to upload the run log at the end of each run.
• To close the dialog box and discard your changes since the last time you chose Apply, choose Cancel.
¾ To set channel options for a 900 Series Interface:
1. Choose Data Channels from the Instrument menu to open the Data Acquisition dialog box with the Data Channels tab selected.
2. Under Data Channel, select channel A, B, or Dual. 3. Select the required Voltage Range.
The required Voltage Range depends on the magnitude of the output signal from the chromatograph detector.
4. Under Set Data Rate, do one of the following to set the rate at which the instrument samples its detectors:
• Select By Peak Width At Base, and then enter the number of seconds in the text box.
With this option, TotalChrom acquires data in terms of the width (at its base) of the narrowest peak that you expect to occur in the run. If you enter a peak width, TotalChrom calculates the optimum sampling rate for that peak width, collecting at least 20 data points across the peak. • Select By Sampling Rate and enter a rate in the text box.
With this option, TotalChrom acquires data from the instrument using the number of data points per second that you explicitly set (or the
If your power line frequency is 60 Hz, you must enter a sampling rate as follows:
• for single- and dual-channel acquisition, a rate that is evenly divisible into 100.
For example: 10 pts/s is acceptable as entered; however, TotalChrom changes 12 pts/s to 12.5 pts/s.
If your power line frequency is 50 Hz, you must enter a sampling rate as follows:
• for single-channel acquisition, a rate that is evenly divisible into 50.
• for dual-channel acquisition, a rate that is evenly divisible into 25.
If necessary, TotalChrom will change your entry for sampling rate to conform to this requirement. This is done to prevent the excessive baseline noise that may be produced with certain detector grounding configurations with older, generic interfaces.
5. In the Delay Time text box, enter the number of minutes that you want to elapse between the start of the run and when peak detection starts. 6. In the Run Time text box, enter the number of minutes that you want the
interface to collect data.
Note that TotalChrom will not allow the delay time to be greater than the run time.