Keysight P9241, Scpi Programmer'S Manual

Page: 1002 / 1344

1002 Keysight P9241/42/43A Oscilloscopes SCPI Programmer's Guide
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:WAVeform Commands
Peak detect display mode is used to detect glitches for time base settings of
500 us/div and slower. In this mode, the oscilloscope can sample more data than
it can store and display. So, when peak detect is turned on, the oscilloscope scans
through the extra data, picks up the minimum and maximum for each time bucket,
then stores the data in an array. Each time bucket contains two data sample.
The array is transmitted over the interface bus linearly, starting with time bucket 0
proceeding through time bucket n-1, where n is the number returned by the
:WAVeform:POINts? query (see page 1010 ). In each time bucket, two values are
transmitted, first the minimum, followed by the maximum. The first pair of values
corresponds to the time bucket at the leftmost side of the screen. The last pair of
values corresponds to the time bucket at the far right side of the screen. In
:ACQuire:TYPE PEAK mode (see page 242 ), the value returned by the
:WAVeform:XINCrement query (see page 1029 ) should be doubled to find the time
difference between the min-max pairs.
HRESolution Data
The high resolution ( smoothing ) mode is used to reduce noise at slower sweep
speeds where the digitizer samples faster than needed to fill memory for the
displayed time range.
Data Conversion
Word or byte data sent from the oscilloscope must be scaled for useful
interpretation. The values used to interpret the data are the X and Y references, X
and Y origins, and X and Y increments. These values are read from the waveform
preamble. Each channel has its own waveform preamble.
In converting a data value to a voltage value, the following formula is used:
voltage = [(data value - yreference) * yincrement] + yorigin
If the :WAVeform:FORMat data format is ASCii (see page 1009 ), the data values
are converted internally and sent as floating point values separated by commas.
In converting a data value to time, the time value of a data point can be
determined by the position of the data point. For example, the fourth data point
sent with :WAVeform:XORigin = 16 ns, :WAVeform:XREFerence = 0, and
:WAVeform:XINCrement = 2 ns, can be calculated using the following formula:
time = [(data point number - xreference) * xincrement] + xorigin
This would result in the following calculation for time bucket 3:
time = [(3 - 0) * 2 ns] + 16 ns = 22 ns
In :ACQuire:TYPE PEAK mode (see page 242 ), because data is acquired in
max-min pairs, modify the previous time formula to the following:
time=[(data pair number - xreference) * xincrement * 2] + xorigin
Data Format for Transfer