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Triggering
Operating Basics
Holdoff Holdoff
Trigger Points
Trigger Level
Holdoff
Acquisition
Interval
Acquisition
Interval
Triggers are Not Recognized During Holdoff Time
Figure 2-2: Trigger Holdoff Time Ensures Valid Triggering
Holdoff is settable from 0% (minimum holdoff available) to 100% (maximum
available). To see how to set holdoff, see
Mode & Holdoff
on page 3-37. The
minimum and maximum holdoff varies with the horizontal scale. See
Holdoff,
Variable, Main Trigger
in the TDS 520A, 524A, 540A, & 544A
Performance
Verification Manual
, Section 2 on
Specification, Typical Characteristics
for
typical minimum and maximum values.
Trigger coupling determines what part of the signal is passed to the trigger
circuit. Available coupling types include AC, DC, Low Frequency Rejection,
High Frequency Rejection, and Noise Rejection:
DC coupling
passes all of the input signal. In other words, it passes both
AC and DC components to the trigger circuit.
AC coupling
passes only the alternating components of an input signal.
(AC components above 10 Hz are passed if the source channel is in
1 M coupling; above 200 kHz are passed in 50 coupling.) It removes
the DC components from the trigger signal.
High frequency rejection
removes the high frequency portion of the trig-
gering signal. That allows only the low frequency components to pass on
to the triggering system to start an acquisition. High frequency rejection
attenuates signals above 30 kHz.
Low frequency rejection
does the opposite of high frequency rejection.
Low frequency rejection attenuates signals below 80 kHz.
Noise Rejection
lowers trigger sensitivity. It requires additional signal
amplitude for stable triggering, reducing the chance of falsely triggering
on noise.
Coupling