Measuring The Time Between Burst Pulse #1 And #4 - Fluke PM6690 Operator's Manual

Measurement Control
#3 Measuring the Time
Between Burst Pulse #1 and
#4
In the previous examples, the synchronization
task has been to identify the start of a mea-
surement and to perform a single-shot time in-
terval measurement. Now, we will complicate
the picture even more. In our next example we
will not only arm the start, but also the stop of
a measurement. We will measure the time be-
tween the first and the fourth pulse in the
pulse burst. We still have the SYNC signal
available, see Fig. 5-13.
S y n c E
I n p u t A
1 2 3
Fig. 5-13 Measuring a time interval inside
a burst.
The measurement function is not Pulse Width
A but Time Interval A to A where the set-
tings for input B are used for controlling the
stop conditions. The desired start and stop
trigger points are marked in the preceding il-
lustration. Our task is now to arm both the
start and the stop of this measurement. The
start arming is already described in example
#1, i.e., synchronize measurement start to the
leading edge of the first pulse. The challenge
is to synchronize the stop of the measurement,
i.e., to arm the stop. If we do nothing, the time
interval measured will be the time between the
first and the second pulse. We must thus delay
the stop. This can be done in different ways.
n
A. Using Trigger Hold Off to
Delay the Stop a Certain Time
Trigger Hold Off is used to inhibit stop trig-
gering during a preset time. The Hold Off pe-
5-12 Arming Examples
4
riod starts synchronously with the start trigger
event. The Hold Off time should be set to ex-
pire somewhere between pulse number 3 and
4, see Fig. 5-14.
S t a r t A r m
T r i g g e r H o l d O f f
I n p u t A
Fig. 5-14 If Hold Off expires between
pulses three and four, the cor-
rect time interval is measured.
Use the same test setup as in the preceding
examples. Then proceed as follows:
–
Use the MEAS/FUNC key to select
Time Interval A to A.
–
Press INPUT B and choose positive slope
and a suitable trigger level.
Press SETTINGS ®Trigger Hold Off
–
(On) and enter a suitable Hold Off time.
–
Make sure the start arming conditions
from example #1 are maintained, i.e. no
arming delay.
–
Measure.
n
B. Using Stop Arming (i.e.,
External Hold Off) to Delay the
Stop
So far in our examples, the sync signal has
been used exclusively as a start arming signal;
i.e., we have been concerned only about the
leading edge of the sync signal, and not its du-
ration. However, the sync signal can also be
used as an External Trigger Hold Off when
you select stop arming on the trailing edge of
the sync signal. If the duration of the sync
pulses can be externally varied, we can select