Keithley 2790, Reference Manual

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C-8 Model 2790 SourceMeter
®
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klqb
For the following discussion, a “data array” is defined as the group of data
elements that are included with each measured reading. Each data array
includes the reading as well as the channel, reading number, units, timestamp,
and limits result (see
“FORMat:ELEMents <item list>,” page 14-6 , for details).
For example, assume the selected data elements to be returned by a read com-
mand include the reading, units designator, and reading number. Now assume a
1VDC input and the READ? command is sent to trigger two readings and return
the two data arrays. The two returned data arrays would look like this:
+1.0000VDC, +00000RDNG#, +1.0000VDC. +00001RDNG#
(Data Array #1) (Data Array #2)
SENSe and sample buffer
The TRACe:CLEar command clears the data store, INITiate:CONTinuous OFF command
disables continuous initiation, and TRIGger:COUNt 1 configures the instrument to perform
one measurement cycle. The INIT command can then be used to initiate the measurement
cycle. When the INIT command is sent, the programmed number of measurements (set by
the SAMPle:COUNt command) are performed and the respective data is temporarily stored
in the sample buffer.
For example, if 20 measurements were performed (SAMP:COUN 20), then 20 data
arrays will be stored in the sample buffer. Data from this buffer is then routed to other
enabled data flow blocks. The data in the sample buffer remains there until data from
another measurement cycle overwrites the buffer.
klqb
The trigger count (TRIG:COUN) determines how many measurement cycles are
performed. However, only the data arrays for the last measurement cycle end up in
the sample buffer. For example, assume TRIG:COUN 2 and SAMP:COUN 20. The
first measurement cycle stores 20 data arrays in the sample buffer. The second
measurement cycle then overwrites the 20 data arrays in the sample buffer.