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Query Usage

Command headers immediately followed by a question mark (?) are

queries. After receiving a query, the instrument interrogates the

requested function and places the response in its output queue. The

output message remains in the queue until it is read or another command

is issued. When read, the message is transmitted across the bus to the

designated listener (typically a controller). For example, the logic

analyzer query

:MACHINEl:TWAVEFbRM:RANGE?

places the

current seconds per division full scale range for machine 1 in the output

queue. In BASIC, the input statement

ENTER XXX; Range

passes the value across the bus to the controller and places it in the

variable Range.

Query commands are used to find out how the instrument is currently

configured. They are also used to get results of measurements made by

the instrument. For example, the command

:MACHINE1:‘lWAVEFORM:XOTIME?

instructs the instrument to

place the X to 0 time in the output queue.

p’

Note

The output queue must be read before the next program message is sent.

or example, when you send the query

:TWAVEFORM:XOTIME?

you

must follow that with an input statement. In BASIC, this is usually done

with an ENTER statement.

Sending another command before reading the result of the query will

cause the output buffer to be cleared and the current response to be lost.

This will also generate a “QUERY UNTERMINATED” error in the

error queue.

HP 1650B/HP 1651B

Programming Reference

Introduction to Programming an Instrument

1-7

HP 1650B User Manual

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