Applied Biosystems Data Explorer 4 Series User Manual page 344

Chapter 8 Viewing Voyager PSD Data
How the
composite
spectrum is
generated
8
PSD calibration
equation
8-6 Applied Biosystems
The software does the following to generate a composite
spectrum:
• Evaluates all segments in the .DAT file to determine if
there are multiple segments acquired using the same
PSD Mirror Ratio.
• If there are duplicates, selects the most recently acquired
segment to include in the composite spectrum.
• Using the precursor ion mass and calibration constants
from the PSD calibration in the .DAT file (see "PSD
calibration equation" below), determines the region of
each segment to include in the composite spectrum as
illustrated in Figure 8-3 on page 8-7.
• Applies baseline correction and two-standard-deviation
noise removal to the composite region of each segment.
• "Stitches" the composite regions together and displays
the composite spectrum.
The equation that the Voyager software uses to calculate the
mass for fragment ions is:
m
( R + ) t
f =
i
where:
m = Fragment ion mass
f
= Calibration constants
,
R = Mirror Ratio
i
t = Fragment ion flight time
f
t = Precursor ion flight time (at R
p
during acquisition
m = Precursor ion mass entered in PSD Acquisition settings
p
before acquisition, or changed in PSD Processing
2
– t ) + t – t ) ] +
f p f p
= 1) calculated
i
R +
i
m
p
+