HP 86140A Series User Manual page 52

Setup panel
selections
Using the Optical Spectrum Analyzer
The Amplitude Menus
Reference Level Position
The value selected for the Reference Level Position determines the position of
the reference level on the graticule. Setting this value to zero divisions places
the reference level on the very bottom of the grid. Setting the reference level
to 10 divisions places the reference level at the top of the grid. Pressing the
front-panel Preset key resets the reference level to 9.0 divisions.
Note
When using the knob or step keys, the value will automatically change. When using the
numeric entry pad, a terminator must be selected from the softkey panel.
Amplitude Units
Selecting Auto for amplitude units allows power to be shown in dBm when
using the logarithmic scale and in watts when using the linear scale. Selecting
W forces the readout to be in watts, regardless of the amplitude scaling.
Auto Ranging
The Auto Range function allows the OSA to change the gain of the transim-
pedance amplifier during a sweep. This provides measurements to be made at
the widest dynamic range and at the fastest sweep speed.
Pressing the front-panel Preset key turns Auto Ranging
Note
It is recommended that Auto Ranging always be turned
Auto Zero
Turns Auto Zero and
ON
be zeroed between sweeps. Selecting
front-panel Preset key resets this function to
Note
Turning Auto Zero allows the instrument to sweep faster, but results in less accu-
OFF
racy on low level signals.
3-12
. Auto Zero enables the internal amplifiers to
OFF ON
disables this feature. Pressing the
OFF
ON
.
ON
.
ON
.