Keithley 2790, Reference Manual

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3-40 Model 2790 SourceMeter
®
Swich System Reference Manual
:READ?
Actions
This command performs three actions. It will reset the trigger model to the idle layer
(equivalent to the :ABORt command), take the trigger model out of idle (equivalent to the
:INIT command), and return a reading (equivalent to a “:FETCh?” query). This command
will always return a new reading, since aborting the trigger model will invalidate any old
readings and trigger a new one. This query will “wait” for a new reading to become avail-
able before the instrument sends a result back.
Limitations
This command will not work if the trigger source is set for BUS or EXTERNAL. This will
cause a –214, “Trigger deadlock” error. Under this condition, one should use a “:FETCh?”
query or a “:DATA:FRESh?” query (
see page 3-41 ). If the trigger model is continuously
initiating (:INIT:CONT ON), sending this query may cause a –213, “Init ignored” error,
but will still give a new reading.
When appropriate
If the Model 2790 receives a *RST command, then it defaults to :INIT:CONT OFF,
:TRIG:SOUR IMM, and :TRIG:COUNT 1. Sending a “:READ?” query under these con-
ditions will trigger a new reading.
:MEASure[:<function>]?
Actions
This query will reconfigure the instrument to the function specified in the query, set the
trigger source for immediate, set the trigger count to 1, and configure the measurement
parameters to *RST defaults. It will then trigger a single reading and return the result.
Limitations
This query is much slower than a “:READ?” or “:FETCh?” query because it has to
reconfigure the instrument each time it is sent. It will reset the NPLC, autoranging, and
averaging to default settings.
When appropriate
This is an ideal command for taking one-shot measurements if the default settings for a
measurement are appropriate and speed is not a requirement.