6482-901-01 Rev. A / August 2012
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B-3
Model 6482 Dual-Channel Picoammeter / Voltage Source Reference Manual
Appendix B: Data Flow
SENS1 and SENS2
The SENS1 and SENS2 blocks represent the basic measured current readings for channel 1 and
channel 2 respectively. If the filter is enabled, the readings will be filtered. The SENSE blocks also
measure time for the timestamp.
INIT
When the INITiate command is sent, the programmed number of source and measure operations
are performed, and the respective data is temporarily stored in a sample buffer. For example, if 20
source and measure operations were performed, then 20 sets of data will be stored in the Buffer.
Data from this buffer is then routed to other enabled data flow blocks.
Assuming that all functions are enabled, the data that is output by the read commands (FETCh?,
CALCX:DATA?, and TRACe:DATA?) depend on which data elements are selected. With all
elements selected, available data will include channel 1 and channel 2 measurements as well as
the timestamp and status information. Note that if a channel is not enabled, then either the NAN
(not a number) value or the source value will be used instead. See
,
for details.
After all source and measure operations are completed, the Model 6482 returns to the idle state.
The data stored in the sample buffer will remain there until data from another source-measure
cycle overwrites the buffer. Data in the sample buffer is lost if the Model goes to the local state
(REM indicator off).
NOTE
With no data in the Sample Buffer, the FETCh? and CALCulateX:DATA? commands to
read data will display the message Data corrupt or stale.
FETCh?
This command is used to read data stored in the sample buffer. If, for example, there are 20 data
sets stored in the sample buffer, then all 20 data sets will be sent to the computer when FETCh? is
executed. Note that FETCh? does not affect data in the sample buffer. Thus, subsequent
executions of FETCh? acquire the same data.
READ?
The READ? command performs an INITiate and then a FETCh? The INITiate triggers a new
source and measure cycle which puts new data in the sample buffer. FETCh? reads that new data.
The MEASure? command places the Model 6482 in a single source and measure mode and then
performs a READ?. See
for more information on READ? and MEASure?.
CALCulate[1]:DATA? and CALCulate2:DATA?
If CALCulate1 or CALCulate2 is enabled, SENS1 or SENS2 data is fed to the CALC1 (channel 1)
or CALC2 (channel 2) block where the results for the selected math function are calculated. The
CALC1:DATA? or CALC2:DATA? command will read the results of the math function. If CALC1 or
CALC2 is enabled, that block is bypassed, and SENS1 or SENS2 data is fed directly to CALC3 or
CALC4.
CALCulate3:DATA? and CALCulate4:DATA?
If CALCulate3 or CALCulate4 (channel 1 or channel 2 REL) is enabled, data is fed to the CALC3
(channel 1) or CALC4 (channel 2) block where the programmed or acquired REL value is
subtracted from the data. CALC3 data comes from either CALC1 or SENS1, depending on the
selected feed. Similarly, CALC4 data comes from CALC2 or SENS2, depending on the selected
feed. The CALC3:DATA? or CALC4:DATA? command will read the results of the REL operation.
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