Tektronix PSM3000 Series, Руководство пользователя

Страница: 35 / 76

Power Meter Application
For the upper and lower limit, the value can be equal outside the limit, equal
between the limit, or equal to one of the limits. Any condition may be speci
fi ed as
pass or fail.
Averaging Two types of averaging are available to use in the Power Meter application to
improve the stability of measurements, especially at low-levels: Averaging and
Extended Averaging.
The Averaging function averages some number of measurements and then
displays the averaged value. You can change the number of measurements that
are averaged from 1 to 100,000. By default, 75 measurements are averaged for
each displayed reading.
Averaging also has the effect of expanding the measurement interval. This
increases the amount of data used to determine peak pulse power, crest factor, and
duty cycle. For signals with narrow pulses or fast peaks, increase averaging to
achieve stable peak power, crest factor and duty cycle measurements.
For example, each raw measurement takes about 250 μ s. Setting the averaging
to 10,000 would result in a 250 μ s x 10,000 = 2.5 s delay between displayed
readings. The average is calculated before each reading is displayed. If averaging
is set high, then the display updates slowly.
Extended Averaging /
Reset
You can combine Averaging and Extended Averaging to balance stability and
responsiveness for your application and preference.
With the Ext Avg / Reset button and Measurement drop down menu, you can set,
enable, and reset extended averaging. Extended averaging should be seen as an
adjunct to averaging: it may be used to further smooth readings and does not slow
down the display update rate as does averaging.
Since extended averaging applies a running exponential average of the last n
readings, where n is the number of extended averages, the display updates quickly
but the measurements respond to changes more slowly. The Reset button resets or
restarts both the max hold and extended averaging functions.
An xAvg indicator will appear in the digital display when extended averaging is
enabled and set greater than 1.
Max / Reset
Retains the maximum measured value until reset or deactivated. For pulse
measurements, each reading (Pulse, Peak, CrF, Avg, DC) is held at its maximum
value independent of the other readings. You can reset or restart this function by
clicking on Reset. You can also
fi nd this item in the Measurement drop down
menu.
A MAX indicator will appear in the digital display when Max hold is enabled.
RF and Microwave Power Sensors/Meters 21