Burst Measurements Using Manual; Presetting - Fluke PM6690 Operator's Manual

Burst Measurements using
Manual Presetting
You can measure the frequency on Input A
and Input B to 300 MHz and on Input C with
limited specifications to the upper frequency
limit of the prescaler with the internally syn-
chronized BURST function as follows:
–
Select Freq Burst under the Freq menu
–
Select A, B, or C as measurement input.
–
Press SETTINGS and Burst. Select a
Meas Time that is shorter than the burst
duration minus two CW cycles.
If you do not know the approximate burst pa-
rameters of your signal, always start with a
short measurement time and increase it gradu-
ally until the readout gets unstable.
–
Press Sync Delay and enter a value lon-
ger than the burst duration and shorter
than the inverse of the PRF. See Fig. 4-3.
B u r s t
S i g n a l
Fig. 4-3 Set the sync delay so that it ex-
pires in the gap between the
bursts.
–
Press Start Delay and enter a value lon-
ger than the transient part of the burst
pulse.
–
Select Frequency Limit (160/300 MHz)
if Input A or Input B is to be used. Use
the low limit if possible to minimize the
number of cycles necessary to make a
measurement.
–
Press EXIT/OK to measure.
All relevant burst parameters can be read on
the display simultaneously.
n
Fig. 4-4
The measurement time must be shorter than
the duration of the burst. If the measurement
continues during part of the burst gap, no mat-
ter how small a period of time, then the mea-
surement is ruined. Choosing a measurement
time that is too short is better since it only re-
duces the resolution. Making burst frequency
measurements on short bursts means using
short measurement times, giving a poorer res-
S y n c . d e l a y
olution than normally achieved with the coun-
ter.
n
The sync delay works as an internal start arm-
ing delay: it prevents the start of a new mea-
surement until the set sync delay has expired.
See Fig. 4-5.
After the set measurement time has started,
the counter synchronizes the start of the mea-
surement with the second trigger event in the
burst. This means that the measurement does
Measuring Functions
Selecting Measurement Time
Three time values must be set to
measure the correct part of a
burst
How Does the Sync Delay
Work?
BURST A, B, C 4-5