added after the pulse drops below the threshold. The window gate extends until the pulse is 75% of the
initial threshold.
l
Width
The current width is measured by the electronics.
Digital electronics
BD FACSymphony™ A1 electronics digitize the signal intensity produced by a detector. The digitized data is
stored in memory and further processed by the electronics to calculate:
l
Pulse height and area
l
Compensation
l
Parameter ratios
These results are transferred to your workstation computer for further processing by BD FACSDiva™ software.
For more information about digital theory, see Digital Theory in the
BD FACSDiva™ Software Reference Manual
.
Threshold
The threshold is the level at which the system starts to measure signal pulses. A threshold is defined for a
specific detector signal. The system continuously samples the digitized signal data and calculates pulse area
and height for all channels based on the time interval during which the threshold is exceeded.
Thresholds can also be set for more than one parameter, and pulse measures are based on either of the
following:
l
Intervals during which ALL signals exceed their threshold value (AND threshold in the software)
l
Intervals during which ANY signal exceeds its threshold value (OR threshold in the software)
Laser controls
Controls in the Laser tab of the Cytometer window are used to manually set the (laser) delay, area scaling, and
window extension values.
These parameters are set by BD Biosciences service personnel during instrument installation and performance
check and are updated each time you run a performance check.
Note:
Do not otherwise change the settings in the Laser tab unless instructed to do so by BD Biosciences.
Changing the settings affects your data.
See the following screen capture for the correct settings.
86
BD FACSymphony™ A1 Flow Cytometer User's Guide
Summary of Contents for FACSymphony A1 Flow
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