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Chapter 7. Acquiring Data
The Property button opens a second
window, shown in Figure 56, that
allows you to set configuration options.
The “Status” Concept
Every pulse sequence can be divided
logically into “periods” of time. The
standard two-pulse sequence, for
example, can be divided as shown in
Figure 57. This sequence has three
logical periods, referred to in the
diagram as A, B, and C. These periods
are used in controlling the decoupler
“status” (as well as the “homospoil”
status, discussed later in this chapter).
For example, say we want the
decoupler to be on during period A, on
during period B, and off during period
C. Using the letter n to signify “no” or
an “off-status,” and y to signify “yes”
Figure 56. Property Button Window
or an “on-status,” we could then
(dps Program)
describe the desired decoupler status as
'yyn'. Setting dm='yyn' will select this experiment, which in the heteronuclear case
might produce a coupled spectrum with NOE, or in the homonuclear case might be used
for solvent presaturation experiments. dm='nny' would give us an experiment with the
decoupler only on during period C, the acquisition time, which in the heteronuclear case
would be a decoupled spectrum without NOE.
p1
pw
d1
A
d2
B
at
C
Figure 57. Logical Periods A, B, C in Standard Two-Pulse Sequence
Observe Transmitter and Decoupling Parameters
On all systems, transmitter power levels are set through attenuators, which are in turn
controlled through a number of parameters. Figure 58 and Figure 59 show schematics for
the attenuator configuration for different systems.
The parameter tpwr sets the observe transmitter power, which is under computer control
on systems with linear amplifiers. tpwr can be given values from 0 to 63, or from –16 to
63, depending on the range of attenuators present in the system. In both cases, 63 is the
maximum possible power.
The first decoupler mode parameter dm determines first decoupler output: if dm='y', the
first decoupler is on, and if dm='n', the first decoupler is turned off. On UNITYINOVA and
UNITYplus systems, setting dm to 'a' or 'y' specifies the asynchronous mode. In this
mode, the decoupler rf is gated on and modulation is started at random places in the
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Getting Started: VNMR 6.1B
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