MDO3000 Programmer Manual.pdf - 第132页

Command Groups X 1 = -500ms + 1ms *( 1-1 ) = -500ms X 2 = -500ms + 1ms * (2 - 1) = -499ms .. . X 1000 = -500ms + 1ms * (1000 - 1) = 499ms V ertical (amplitude) values: Y i =Y Z E r o+( Y M U l t*D a t a P o i n t i ) = 0…

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Command Groups
Scaling Waveform Data
Once you transf
er waveform data from an oscilloscope to a computer, you can
convert the data points (which are digitizing levels) into engineering units such as
Volts or Amps for analysis using information from the waveform preamble.
The following is an example for converting transferred data into the appropriate
engineering units. The transfer data is from an analog waveform in YT (single
point) format. (See WFMInpre:PT_Fmt for the definition of the point
formats.)
The data points returned from the
CURVE? query for analog channel data are in
digitizing levels. The YMULT value is in vertical units (e.g. volts) per digitizing
level.
Formula for computing horizontal (time) point value:
X
i
= XZEro + XINcr * (i - 1)
Formula for computing vertical (amplitude) point value:
Y
i
= YZEro + (YMUlt * DataPoint
i
)
where:
i is the index of a curve data point (1–based: first data point is point number 1)
X
i
is the ith horizontal value in XUNits
Y
i
is the ith vertical value in YUNits
DataPoint
i
is the waveform data point value, in digitizing levels.
Commands used:
:DATa:SOUrce CH1
:DATa:START 1
:DATa:STOP 1000
:WFMOutpre:NR_pt? 1000
:WFMOutpre:XUNit? “s”
:WFMOutpre:XZEro? -500.000E-3
:WFMOutpre:XINcr? 1.0000E-3
:WFMOutpre:YUNit? “V”
:WFMOutpre:YZEro? 0.0E+0
:WFMOutpre:YMUlt? 4.0000E-3
:WFMOutpre:BYT_nr? 1
Horizontal (time) values:
X
i
=XZEro+XINcr*(i-1)
=-500ms+1ms*(i–1)
MDO4000/B/C, MSO/DPO4000B and MDO3000 Series Oscilloscopes Programmer Manual 2-101
Command Groups
X
1
= -500ms + 1ms
*(1-1)
= -500ms
X
2
= -500ms + 1ms * (2 - 1)
= -499ms
.. .
X
1000
= -500ms + 1ms * (1000 - 1) = 499ms
Vertical (amplitude) values:
Y
i
=YZEro+(YMUlt*DataPoint
i
)
= 0.0V + (0.004 * DataPoint
i
)
YZERO is in vertical units; in this example, 0.0 Volts.
YMULT is in vertical units per digitizing level (DL), in this example,
0.004 Volts per digitizing level.
From
CURVe query:
DataPoint
1
=-10
DataPoint
2
=-11
DataPoint
1000
=23
Y
1
= 0.0V + (0.004V/DL * -10DL) = –0.040V
Y
2
= 0.0V + (0.004V/DL * -11DL) = –0.044V
Y
1000
= 0.0V + (0.004V/DL * 23DL) = 0.092V
Further Explanation of the
Digital Collection
When the waveform source is set to DIGital using the DATa:SOUrce command, a
WFMOutpre? and CURVe? query (or a WAVFRM? query) will return the Digital
Collection data. The format and content of this data will depend upon the width
that has been specified using the
DATa:WIDth command, which can be either
4 or 8 bytes per point.
NOTE. Applies to MSO/MDO4000/B models only as well as MDO3000 and
MDO4000C models with option MDO3MSO or MDO4MSO installed.
4 Byte Data. When the data width is set to 4 bytes (using either DATa:WIDth or
WFMOutpre:BYT_Nr, the Digital Collection represents
the states of digital channe
ls D0 – D15,
the digital representations of analog Channels 1 – 4, and
the trigger state.
2-102 MDO4000/B/C, MSO/DPO4000B and MDO3000 Series Oscilloscopes Programmer Manual
Command Groups
In this case, th
e Digital Collection data returned will be 32-bit packed integers,
where each point is represented as follows. Note that the trigger state bit described
below is only available when ACQuire:MAGnivu is 1 (on).
Table 2-46: Digital Collection: 4 Byte Data
Bit number Description
31– 22 not used
21 trigger state
20
not used (always 1)
19
CH4 digital state
18
CH3 digital state
17
CH2 digital state
16
CH1 digital state
15 D15 state
...
1 D1 state
0 D0 state
8ByteData. When the data width is set to 8 bytes, the Digital Collection
represents
the transition state information for digital channels D0 – D15 and
the digital representations of analog Channels 1 – 4.
The "transition state" refers to MSB and LSB bits which together represent the
state of the digital channel during the sampling period, as fol
lows:
MSB LSB Transition/State
0 0 Low
01High
10
Single transition
1 1 Multiple transitions
If the width specified using the DATa:WIDth command is 8 bytes, the Digital
Collection data returned will be 64-bit packed integers, where each point is
represented as follows:
Table 2-47: Digital Collection: 8 Byte Data
Bit Number Description
63 — 52 not used
51
CH4 trans ition state MS B
50
CH3 trans ition state MS B
49
CH2 trans ition state MS B
MDO4000/B/C, MSO/DPO4000B and MDO3000 Series Oscilloscopes Programmer Manual 2-103