Chapter 2: Theory of Operation 69
Drop Delay Overview
The BD FACSAria cytometer includes integrated Accudrop technology to assist
in setting an accurate drop delay value. Accudrop components consist of the
following:
• a diode laser, mounted to the left of the sort block
• a camera that provides an image of the side streams
• an emission filter for viewing the fluorescence from Accudrop beads
The emission filter is installed in front of the lower camera and can be moved in
and out by clicking the Optical Filter control. When the button is green ( ), the
filter is out. This position is used to view the center and side streams.
Click the button to move the filter in front of the camera when you are
determining the drop delay; the button changes to red ( ). To determine the
drop delay, the streams are illuminated by the diode laser just below the point of
deflection. Specialized fluorescent particles (Accudrop beads) can be viewed in
the center and left side streams as the delay is adjusted. The best delay yields the
most particles in the left stream and the fewest in the center stream. See
Determining the Drop Delay on page 158 for more information.
2nd, 3rd, 4th Drop
fields
Apply a correction factor for the drop charge as a percentage of
the previous drop, from –100% to 100%.
Phase field Adjusts the phase between drop generation and charging of the
droplets from 0–360°.
The selected value is sent to both the drop-charging electrode
and the drop strobe. In general, the Phase never needs
adjusting; you can keep the default value of zero.
Table 2-2 Side Stream window controls
Control Description
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