HP 54501A - Query Command

Query
Command Command
headers
immediately
followed
by a
question
mark
(?)
are
queries.
After
receiving
a
query,
the
instrument
interrogates
the
requested
function and
places
the
answer
in
its
output
queue.
The
answer
remains
in
the
output queue
until
it
is
read
or
another
command
is
issued.
When
read,
the
answer
is
transmitted
across
the
bus
to
the
designated
listener
(typically
a
controller).
The
query
:TIMEBASE:RANGE?
places
the
current
timebase
setting
in
the
output
queue.
The
controller
input
statement:
ENTER
<
device
address
>
;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,
with
the
query
actually activating
the
measurement.
For
example,
the
command
:MEASURE:RISETIME? instructs the
instrument
to
measure
the
risetime of
your waveform
and
place
the
result
in
the
output
queue.
Note
The
output
queue must
be
read
before
the
next
pro/yam
message
is
sent.
For
example,
when
you
send
the
query
:MEASURE:RISETIME?
you
must
follow
that
query
with
the
program
statement
ENTER
Value
jisetime
to read
the
result
of
the
query
and
place
the
result
in
a
variable
(Value
jisetime).
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
an
error
in
the
error
queue.
HP
54501A
Programming
Introduction
to Programming
an
Oscilloscope
1-7