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Remote Operation
SCPI Syntax Rules
Querying data
Data is requested from the instrument using a query. Queries can be used to
find out how the instrument is currently configured. They are also used to
obtain results of measurements made by the instrument, with the query actu-
ally activating the measurement. String responses are returned as uppercase
letters.
Queries take the form of a command followed by a question mark (?). After
receiving a query, the instrument places the answer in its output queue. The
answer remains in the output queue until it is read or another command is
issued. For example, the query
sendMessage":CALCulate:MARKer1:X?"
places the wavelength of marker 1 in the output queue.
Using your language interface to read the response passes the value across the
bus to the controller. Sending another command or query before reading the
result of a query causes the output queue to be cleared and the current
response to be lost. This generates an error in the error queue. The output of
the instrument may be numeric or character data depending on what is que-
ried. Refer to the specific commands for the formats and types of data
returned from queries. You can send multiple queries to the instrument within
a single program message, but you must also read them back within a single
program message. This can be accomplished by either reading them back into
a string variable or into multiple numeric variables. When you read the result
of multiple queries into string variables, each response is separated by a semi-
colon.
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