Instrument Functions
NRP2
66
User Manual 1173.9140.02 ─ 07
"Burst Av"
The
Burst Av
erage mode is used to measure the average burst
power of pulsed signals. The acquisition interval is automatically
derived from the signal (see
chapter 4.2.1.3, "Measuring the average
Remote command:
4.2.1.2
Continuous average-power measurements
The "Cont Av" mode is the preferred measurement method if the measurement is not
to be, or cannot be, synchronized with a specific signal event.
This is the only available measurement mode for thermal power sensors because they
are too slow for the other measurement modes.
► Select "Cont Av" in the "Mode..." dialog box opened via the "Sensor" menu.
Fig. 4-5: Mode dialog box / Cont Av
Aperture
Defines the aperture time (size of the acquisition interval). In the manual operating
mode, the sensor-specific default setting combined with active smoothing (see below)
is usually adequate. A different setting may be required if the result exhibits fluctua-
tions due to modulation.
If the modulation frequency is known, the best results can be achieved with the aper-
ture time set exactly to an integer multiple of the modulation period and smoothing
switched off. If possible, choose the multiple such that the resulting aperture time is
about as high as its sensor-specific default value.
If the modulation frequency is not known or not constant, or if a spread-spectrum mod-
ulation technique is used, smoothing should be switched on. With smoothing on, about
five periods are enough to reduce fluctuations caused by modulation to an acceptable
level. With more than nine periods, the fluctuations are imperceptible. With smoothing
off, the situation is much less favorable as instead of just five periods as many as 300
are required; the fluctuations only completely disappear with more than 3000 periods.
Data acquisition and parameters
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