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Measurements Applications
Measuring Signal-to-Noise Ratios with Averaging
During a signal-to-noise with averaging measurement, the display indicates
S/N A xx,
where A indicates averaging and xx is the number of averages
taken so far. The maximum number of averages is 900, the minimum number
of averages is 10, and the default (Preset) value is 100 averages. A measure-
ment with 100 averages takes about 2 minutes to complete. When the mea-
surement is complete, the instrument switches to single measurement mode.
Then, pressing the
Cont
key will start a completely new measurement. During a
measurement and before the number of averages has been reached, pressing
the
Single
key will stop the measurement. Then, pressing the
Cont
key will con-
tinue with the current measurement.
While making a signal-to-noise with averaging measurement, the number of
averages can be changed. As long as the new number of averages is greater
than the number of averages taken so far, the measurement continues. If the
new number of averages selected is less than the number of averages taken so
far, the measurement stops and the instrument switches to single measure-
ment mode. Then, pressing the
Cont
key will start a completely new measure-
ment.
Noise bandwidth
affects
measurement
When measuring noise power, the Agilent 86120B must account for the noise
bandwidth used during the measurement. Because noise bandwidth varies
with measurement bandwidth (a wide bandwidth allows more noise to the
Agilent 86120B’s detector than a narrow bandwidth), the Agilent 86120B nor-
malizes all noise power measurements to a bandwidth of 0.1 nm. The annota-
tion
0.1 nm
is displayed to show that the noise bandwidth is being
normalized to a 0.1 nm bandwidth.
To measure signal-to-noise with averaging
1
Press the front panel
Preset
key.
2
Press
List by WL
or
List by Power
.
3
Press
Appl's
and then
S/N AVG
.
4
To change the number of averages, press
NUM AVG
. The default (Preset) value
is 100.
5
To stop the measurement at the current number of averages shown, press the
Single
key. Then press the
Cont
key to continue the present measurement.
6
When the measurement is complete, the instrument will switch to the single
measurement mode and stop.
7
To make a new measurement, press the
Cont
key.
8
To exit, press the
EXIT
softkey, then press the
Cont
key for continuous
measurement.