PDA Calibration Window

Function

This window allows you to:

•	Examine wavelength calibration of the diode array and recalibrate if necessary.

•	View the reference spectrum and dark current.

•	View the effects of exposure time on photodiode saturation for a given wavelength range.

Parts of the Window

The PDA Calibration window contains the followng parts:

•	Menu Bar – Displays File, View, Calibration, and Help menus for performing commands in the PDA Calibration window.  For details, click here [image].

•	Tool Bar − Displays shortcut buttons that provide quick access to some commonly used commands in the PDA Calibration window.  For details, click here [image].

•	Plot − Displays Reference spectra from less than 190 nm to more than 800 nm.  Also, displays the Dark spectrum, the 486.0- and 656.1-nm Deuterium Balmer lines as references (black vertical lines), and the 85% lamp energy saturation (black horizontal line).  You can zoom in on any area of the Spectral plot.  You can also pan a zoomed plot using the vertical and horizontal scrollbars.

Note:  The Y-axis for the plot is in analog-to-digital (A/D) converter counts.

•	Controls − Buttons that control zooming, full view, run, and stop; an Exposure time field for the Reference spectrum; and a check box to display the Dark spectrum instead of the Reference spectrum.

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PDA Calibration Accuracy Dialog Box

Use this dialog box to display the accuracy of the detector wavelength readings.  Accuracy numbers are rounded to one decimal place.  If wavelengths are accurate to 1 nm, recalibration is not recommended.

Attention:  Recalibrating your 996 detector wavelength may invalidate your current PDA libraries and may affect future results of library matching.  Recalibrate only when necessary.

If wavelengths are not accurate to within 1 nm, clicking Recalibrate recalibrates the wavelengths.

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PDA Calibration Window Menus

The PDA Calibration window includes the following menus:

 File – Saves and deletes preferences, and exits from the Calibration window.

 View – Displays/hides the deuterium source markers, the toolbar, and the status bar.

 Calibration – Detects marker lines, displays the Calibration Accuracy dialog box, and recalibrates the PDA detector wavelength.

 Help – Accesses the Millennium32 Online Help system, displays window-level Help for the PDA Calibration window, and displays an About dialog box.

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PDA Calibration Window File Menu
File Menu (PDA Calibration)

Save Preferences

Saves the display preferences that you selected for the window.

Delete Preferences

Deletes the display preferences that you selected for the window.

Exit

Exits from the Calibration window.

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PDA Calibration Window View Menu
View Menu (PDA Calibration)

Deuterium Source Markers

Displays the deuterium source markers at 486.0 nm and 656.1 nm in the Spectral plot.

Toolbar

Displays/hides the toolbar, which contains a button that activates Millennium32 context-sensitive Help.

Status Bar

Diplays/hides the Calibration window status bar.

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PDA Calibration Window Calibration Menu
Calibration Menu (PDA Calibration)

Note:  Calibration commands use preset Exposure Time values for calibration.  They do not use the Exposure Time you enter in the PDA Calibration window.

Detect Lines

Reads the optics bench calibration values (Lambda1 and Lambda512) and displays vertical default colored lines at the points in the spectrum where the 486.0-nm and 656.1-nm peaks appear.

Calibration Accuracy

Displays the Calibration Accuracy dialog box [image].

Recalibrate

Recomputes Lambda1 and Lambda512 and sends the new calibration parameters to the optics bench of the 996 detector.  Prior to recalibrating the 996 PDA detector, the software displays a warning message about the effects of recalibrating.

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PDA Calibration Window Help Menu
Help Menu (PDA Calibration)

Millennium Help Topics

Accesses the Help Topics Browser of the Millennium32 Online Help System.  The browser has three tabs (Contents, Index, and Find) that provide you with the flexibility to navigate through all topics found in the Help system.

Help on PDA Calibration

Accesses the Help topic for the PDA Calibration window (same as pressing F1).

About PDA Calibration

Displays the software version, copyright information, and system resource usage.

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PDA Calibration Window Toolbar

The PDA Calibration Window toolbar contains the following tool:

Tool	Function
(Context-sensitive Help tool)	Displays context-sensitive Help for the object you click after clicking this tool.
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Dark Spectrum

Photodiodes lose charge over time even when they are not exposed to light.  The amount of charge lost by the photodiodes when they are not exposed to light is called dark current.

At the start of a chromatographic run, the Waters 996 detector closes the shutter to take a dark current reading for each photodiode.  The shutter closes after the exposure time is calculated and stays shut for the same interval as the exposure time.

The detector subtracts the dark current values from the current values that are recorded for both the sample and the reference spectra.

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Saves the display preferences that you selected for the window.


Deletes the display preferences that you selected for the window.


Displays the deuterium source markers at 486.0 nm and 656.1 nm in the Spectral plot.


Reads the optics bench calibration values (Lambda1 and Lambda512) and displays vertical colored lines at the points in the spectrum where the 486.0- and 656.1-nm peaks appear.


Displays the Calibration Accuracy dialog box, which displays the accuracy of the wavelength readings.


Recomputes Lambda1 and Lambda512 values and sends the new calibration parameter values to the optics bench of the 996 detector.  Prior to recalibrating the 996 PDA detector, the software displays a warning message about the effects of recalibrating.


Returns the Reference Spectrum plot or the Dark Spectrum plot to the full range of values in both axes.


Undoes one zoom level after you have drawn one or more zoom boxes to enlarge an area of the Reference spectrum or the Dark spectrum.


The time in milliseconds that the photodiode array is exposed to the lamp in the 996 PDA detector.


Displays the dark spectrum, which is a plot of the electrical current discharged from the photodiode array with the shutter closed.


Acquires and displays the Reference spectrum using the specified exposure time and dark spectrum settings.


Halts the acquisition of the Reference spectrum or the Dark spectrum (if selected).  If you want to calibrate or to zoom spectral features, click Stop first.


Recomputes Lambda 1 and Lambda 512 values and sends the new calibration parameter values to the optics bench of the 996 PDA detector.


Displays Reference spectra from less than 190 nm to more than 800 nm.  Also, displays the Dark spectrum, the 486.0- and 656.1-nm deuterium Balmer lines (black vertical lines), and the 85% lamp energy saturation level (black horizontal line).  You can zoom in on any area of the Spectral plot.  You can also scan a zoomed plot using the vertical and horizontal scrollbars.

Note:  The Y-axis for the plot is in analog-to-digital ( A/D) converter counts.