a duration that expires in the gap between
pulse #3 and #4.
Use the same test setup as in the preceding ex
-
ample. Then proceed as follows:
–
Press SETTINGS ® Arm and select
Stop Chan E and negative Stop Slope.
–
Measure.
#4 Profiling
Profiling means measuring frequency versus
time. Examples are measuring warm-up drift
in signal sources over hours, measuring the
linearity of a frequency sweep during seconds,
VCO switching characteristics during milli
-
seconds, or the frequency changes inside a
“chirp radar” pulse during microseconds.
These counters can handle many profiling
measurement situations with some limitations.
Profiling can theoretically be done manually,
i.e., by reading individual measurement re
-
sults and plotting in a graph. However, to
avoid getting bored long before reaching your
800th or so measurement result, you must use
some computing power and a bus interface. In
profiling applications, the counter acts as a
fast, high-resolution sampling front end, stor
-
ing results in its internal memory. These re
-
sults are later transferred to the controller for
analysis and graphical presentation. The
TimeView™ software package greatly simpli
-
fies profiling.
You must distinguish between two different
types of measurements called free-running
and repetitive sampling.
n
Free-Running Measurements
Free-running measurements are performed
over a longer period, e.g., to measure the sta
-
bility over 24 hours of oscillators, to measure
initial drift of a generator during a 30-minute
warm-up time, or to measure short-term sta
-
bility during 1 or 10s. In these cases, measure
-
ments are performed at user-selected intervals
in the range 2 ms to 1000 s. There are several
different ways of performing the measure
-
ments at regular intervals.
Measurements using the statistics
features for setting the “pacing time”
By setting the pacing time to 10 s for exam-
ple, measurements are automatically made at
10 s intervals until the set number of samples
has been taken. The range is 2 - 2
*
10
9
.Use
HOLD/RUN and RESTART if you want to
stop after one full cycle. You can watch the
trend or spread on the graphic display while
the measurement is proceeding.
Using a controller as a “pacer”
As an alternative, the timer in the controller
can be used for pacing the individual measure
-
ments. This allows for synchronization with
external events, for instance a change of DUT
when checking a series of components.
Using external arming signals
External arming signals can also be used for
“pacing.” For example with an arming signal
consisting of 10 Hz pulses, individual mea
-
surements are armed at 100 ms intervals.
Letting the counter run free
When the counter is free-running, the shortest
delay between measurements is approximately
4 ms (internal calibration OFF) or 8 ms (inter
-
Arming Examples 5-13
Measurement Control
S y n c E
S t a r t A r m i n g
I n p u t A
S t o p A r m i n g
Fig. 5-15 Using both start and stop arm
-
ing to select the part of the
burst that is of interest.
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