326 Chapter5
Language Reference
SENSe Subsystem
Spectrum—ADC Range
[:SENSe]:SPECtrum:ADC:RANGe
AUTO|APEak|APLock|M6|P0|P6|P12|P18|P24|
[:SENSe]:SPECtrum:ADC:RANGe?
Select the range for the gain-ranging that is done in front of the ADC.
This is an advanced control that normally does not need to be changed.
Auto peak ranging is the default for this measurement. If you are
measuring a CW signal please see the description below.
• Auto - automatic range
For FFT spectrums - auto ranging should not be not be used. An
exception to this would be if you know that your signal is
“bursty”. Then you might use auto to maximize the time domain
dynamic range as long as you are not very interested in the FFT
data.
• Auto Peak - automatically peak the range
For CW signals, the default of auto-peak ranging can be used, but
a better FFT measurement of the signal can be made by selecting
one of the manual ranges that are available: M6, P0 - P24.
Auto peaking can cause the ADC range gain to move
monotonically down during the data capture. This movement
should have negligible effect on the FFT spectrum, but selecting a
manual range removes this possibility. Note that if the CW signal
being measured is close to the auto-ranging threshold, the noise
floor may shift as much as 6 dB from sweep to sweep.
• Auto Peak Lock - automatically peak lock the range
For CW signals, auto-peak lock ranging may be used. It will find
the best ADC measurement range for this particular signal and
will not move the range as auto-peak can. Note that if the CW
signal being measured is close to the auto-ranging threshold, the
noise floor may shift as much as 6 dB from sweep to sweep.
For “bursty” signals, auto-peak lock ranging should not be used.
The measurement will fail to operate, since the wrong (locked)
ADC range will be chosen often and overloads will occur in the
ADC.
• M6 - manually selects an ADC range that subtracts 6 dB of fixed
gain across the range. Manual ranging is best for CW signals.
• P0 to 24 - manually selects ADC ranges that add 0 to 24 dB of fixed
gain across the range. Manual ranging is best for CW signals.
Factory Preset
and *RST: Auto peak
Remarks: To use this command, the appropriate mode should be
selected with INSTrument:SELect.
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