Agilent Technologies Infiniium 90000 Q-Series, Programmer'S Manual

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Agilent Infiniium 90000 Series Oscilloscopes
Programmer's Reference
19
Histogram Commands
:HISTogram:AXIS 373
:HISTogram:MODE 374
:HISTogram:SCALe:SIZE 375
:HISTogram:WINDow:DEFault 376
:HISTogram:WINDow:SOURce 377
:HISTogram:WINDow:LLIMit 378
:HISTogram:WINDow:RLIMit 379
:HISTogram:WINDow:BLIMit 380
:HISTogram:WINDow:TLIMit 381
The HISTogram commands and queries control the histogram features. A
histogram is a probability distribution that shows the distribution of
acquired data within a user- definable histogram window.
You can display the histogram either vertically, for voltage measurements,
or horizontally, for timing measurements.
The most common use for histograms is measuring and characterizing
noise or jitter on displayed waveforms. Noise is measured by sizing the
histogram window to a narrow portion of time and observing a vertical
histogram that measures the noise on a waveform. Jitter is measured by
sizing the histogram window to a narrow portion of voltage and observing
a horizontal histogram that measures the jitter on an edge.
Histograms and
the database
The histograms, mask testing, and color grade persistence use a specific
database that uses a different memory area from the waveform record for
each channel. When any of these features are turned on, the oscilloscope
starts building the database. The database is the size of the graticule area.
Behind each pixel is a 21- bit counter that is incremented each time data
from a channel or function hits a pixel. The maximum count (saturation)
for each counter is 2,097,151. You can use the DISPlay:CGRade:LEVels
command to see if any of the counters are close to saturation.
The database continues to build until the oscilloscope stops acquiring data
or all both features (color grade persistence and histograms) are turned
off. You can clear the database by turning off all three features that use
the database.