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Power Measurement
How to Measure Power
84
Agilent 8163A Lightwave Multimeter, Agilent 8164A Lightwave Measurement
System, & Agilent 8166A Lightwave Multichannel System, Fourth Edition
How to Set the Averaging Time
N O T E
For a Dual Power Sensor, you cannot set the averaging time of the slave channel,
channel 2, directly. By default, the averaging time of the slave channel, channel 2,
is the same value as that for the master channel, channel 1. See Table 2 on
page 90 for more details.
This is the length of time over which a signal is averaged. Longer averaging times
increase the accuracy and improve the noise rejection. Longer averaging times
also decrease sensitivity.
For averaging times of 1 second or less, a new measurement is shown at the end
of each averaging time. This is drawn in Figure 53. A new measurement is shown
on the display at each x.
With modules designed for the HP 8153A Lightwave Multimeter, for averaging
times of more than 1 second, the displayed power is given by the formula:
Where,
P
new
is the new displayed result,
P
old
is the previously displayed result,
Sample
is the value read by the hardware,
T
avg
is the averaging time, as set by the user, and
T
sample
is the time the hardware takes to make a reading.
If the measurement condition change (for example, a range change in automatic
ranging),
P
old
is reset and the averaging starts again. This is why the display
update seems faster in automatic ranging.
To set the averaging time to 1 second:
1
Move to the Power Meter channel and press the [Details] softkey.
2
Move to the [
AvgTime
] parameter and press
Enter
.
3
Move to <
1 s
>, by using the cursor key, and press
Enter
.
How to Choose the MinMax Mode
N O T E
For a Dual Power Sensor, you cannot set the MinMax Mode of the slave channel,
channel 2, directly. By default, the MinMax Mode of the slave channel,
Figure 53
Measurements with Tavg
≤
1 second
x
x
x
x
x
x
x
x
T
avg
P
new
P
ol d
1
T
sam pl e
T
av g
------------------
–
Sample
T
sa m pl e
T
avg
------------------
+
=