Sens1 And Sens2; Init; Fetch; Read - Keithley 2500 User Manual

Models 2500 and 2502 User's Manual

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
After all source and measure operations are completed, the Model 2500 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 annunciator off).
NOTE

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 2500 in a one-shot source and
measure mode and then performs a READ?. See
READ? and MEASure?.
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Section 17, "FORMat subsystem,"
With no data in the Sample Buffer, the FETCh? and CALCulateX:DATA? com-
mands to read data will display the message Data corrupt or stale.
Data Flow
for details.
Section 16 for more information on
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