Data Acquisition Options And Detector Selection
These sections of the Method allow you to control how data collection is initiated, the duration and frequency of data acquisition, and the way the runs are named and numbered.
The Channel Selection section allows you to select which detectors will be used for the run. The Epsilon can be configured for up to four simultaneous channels of data collection. Depending on the configuration purchased, you can select various configurations of onboard electrochemical (EC) and external (EXT) detectors.
DATA DESCRIPTION
The Data Description section can be accessed through the Method drop-down Menu:
This section also can be reached by clicking the <
OPERATOR, CONDITIONS and RUN NOTES are user-inserted comments entered into the Method. This information is saved along with every Data file generated by CONTROL. CHROMGRAPH REPORT imports this information and includes it in the final processing report that it generates. By using these fields when you collect data, you will always be able to identify any particular Data file.
During unattended operation you can automatically import sample identifying information into the RUN NOTES section. Click here for details.
DATA NAME is the name used to store the data file. It can have any combination of characters and spaces (the last position must be a letter, to avoid confusion with the run number, which will be appended).
Run numbers (three digits, up to 999) and a letter (A through D, for detector 1 through 4) are automatically appended to the data name by the data-acquisition software. When saved to disk, the name is given the extension .DAT. Thus, CATS003A.DAT is the third run in a series called cats, and contains data from detector A.
Data names can theoretically be up to 127 characters long, including the path (thus, C:\BAS2\DATA\mydata002A.dat = 27 characters). Some advanced procedures may require shorter names, so we recommend using names with total lengths (including the path) of less than 33 characters.
For display purposes, a filename may be truncated somewhat in various places in the program.
DATA ACQUISITION OPTIONS
The Data Acquisition Options section can be accessed through the Method drop-down Menu:
This section also can be reached by clicking the <
The following options are available:
TRIGGER TYPE determines how a chromatographic run will start. There are three types of triggers:
- Manual means you start each run by clicking the RUN button in the Run Status box.
- Automatic means you start the first run by clicking the RUN button in the Run Status box, but that subsequent runs start automatically.
- External means that an external device (e.g. an autosampler) will initiate each run. You must connect the external device to the epsilon's back panel. Before the first trigger arrives you must put the epsilon in the 'waiting for trigger' mode by clicking the RUN button in the Run Status box.
OMIT DATA BEFORE/AFTER allows you to specify the time during which data will be collected and saved. In most cases this is equal to the length of the run, but you may want to shorten the data-collection time if you have a column wash or re-equilibration programmed into the pump schedule.
DATA ACQUISITION RATE is the number of times per minute that detector response is recorded. Too small a rate will result in poor peak resolution. Too large a rate wastes computer resources. We recommend the AUTO setting, in which the optimum rate is decided for you. Alternatively, you may open up this listbox and select rates between 75-1200 points per minute. In all cases the actual data-collection rate is shown in the Run Status box.
FIRST RUN NUMBER is the number that will be given to the first run of a series. This value is incremented by one each time a run is completed. If a series of runs is aborted during a run, the number assigned to the aborted run will remain, so the series can be restarted where it left off.
NUMBER OF RUNS is the number of runs (maximum = 999 for any Data Name) to be made in programmed operation. This number will be decremented by one each time a run is completed. If a series of runs is aborted during a run, the NUMBER OF RUNS will remain at its last decremented value so the series can be restarted where it left off.
If runs are being made manually, one by one, use either '0' or '1' for this parameter.
DETECTOR SELECTION
The number of detectors enabled, and their type, is shown in the Data Acquisition Options screen:
DISABLE ALL CHANNELS allows you to deconfigure all detectors at once. You must do three things to put this change into effect:
- Check the 'Disable' box
- Click the OK button
- Click the EQUIL button in the Run Status box.
CHANGE ... If the detector configuration is not appropriate for the analysis to be done, press the CHANGE button. This brings up the Detector Channel Options screen:
AVAILABLE HARDWARE shows the number of analog circuit boards installed in the epsilon detector. The detector channels available are determined by the number of circuit boards as follows:
| Boards | Channels |
| 1 | 1 |
| 2 | 2 |
| 3 | 3 and 4 |
Click on the configuration that is required for your analyses. The software will not allow you to make selections that are inconsistent with the installed hardware or the requirements of certain modes. In particular:
- Pulsed Amperometric Detection (PAD) precludes the use of any other detector.
- Electrochemical Detectors (W1-W4) must be selected before External Detectors.
- The number of available channels is limited by the number of analog boards purchased with the instrument.
- Detectors are added sequentially; upper channels become available only as the lower channels are filled.
After the detectors are enabled, their conditions must be set in the relevant detector schedules. Detector conditions for on-board EC detectors are set in the EC Detector Schedule and those for PAD are set in the PAD Options section.
Conditions for the External Detectors are set in this screen, but are discussed in the External Detectors LINK section.
DIFFERENCE CHANNEL. The epsilon detector provides a means for monitoring the difference between two chromatograms, in real time. When you click on one of the difference options, the system will do the requested subtraction during the run and graph it continuously. The data file that is generated is saved as a normal file and may be processed and graphed with ChromGraph Report. Please note the following:
- The difference channel will replace one of the original channels.
- An offscale peak in one of the original channels (particularly the one that is replaced, so you can't see it) can have some odd effects on the difference channel.
- Use an insensitive range to keep the peaks on scale.
- Rezero before each run, to keep the peaks on scale.
