HP 54620A, User'S And Service Manual

Page: 135 / 243

The time reference position sets the general location of the trigger event
within acquisition memory. A time reference position of Left sets the event to
a few locations after the beginning of acquisition memory, Center sets the
event to the middle of acquisition memory, and Right sets the event to a few
locations before the end of acquisition memory. The delay setting sets the
specific location of the trigger event with respect to the time reference
position.
Thus, because the delay can be adjusted in the positive
direction to greater than the depth of acquisition memory, the trigger
event may or may not be stored in acquisition memory
. (The range of
available negative delay is less.)
Consider a measurement where the time reference is set to Center, the
sweep speed is set to 5
µ
s/div (sample interval 40 ns), and the delay is set to
75
µ
s. A single acquisition is performed. The result looks like the following:
Single Acquisition, Time Reference Center, Positive Delay of 75
µ
s
The trigger event
is off-screen to
the left
Part of acquisition
memory is
off-screen as well
Figure 38
Ensuring Accurate Measurements
Time base and Acquisition
134