Keithley 2002, Getting Started Manual

Page: 63 / 95

Query commands
With few exceptions, every SCPI command has a corresponding query. A command sets a
control point in the instrument; a query determines the present setting of the control point. The
query is simply the command name with a "?" attached.
Some commands are actions rather than control point settings. These commands have no que-
ry form. For example,
SENSe1:VOLTage:DC:REFerence:ACQuire
is an action command, not a setting, and so has no query form.
There are some queries that have no corresponding command. For example,
SENSe1:DATA?
causes the instrument to return the latest reading. Of course, there is no corresponding command
to send a reading value into the instrument.
Default nodes
SCPI uses the concept of default nodes. Consider the example command tree shown previ-
ously in Figure 16. What is within square brackets is not necessary to send to the instrument, but
the instrument will accept it if you send it. Consider the
:UPPer
command, which sets the mea-
surement range. To set the Mode 2002 to measure 15VDC, any of the following commands
works:
SENSe1:VOLTage:DC:RANGe:UPPer 15
SENSe:VOLTage:DC:RANGe:UPPer 15
SENSe1:VOLTage:DC:RANGe 15
VOLTage:DC:RANGe:UPPer 15
VOLTage:DC:RANGe 15
These are shown in long form, but short forms could also be used.
IEEE-488 Bus Operation 3-9