More About Oscilloscope Commands 43
Keysight InfiniiVision 4000 X-Series Oscilloscopes Programmer's Guide 1617
Query Return Values
Command headers immediately followed by a question mark (?) are queries.
Queries are used to get results of measurements made by the instrument or to find
out how the instrument is currently configured.
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). For example, the query :TIMebase:RANGe? places the
current time base setting in the output queue. When using the Keysight VISA COM
library in Visual Basic, the controller statements:
Dim strQueryResult As String
myScope.WriteString ":TIMebase:RANGe?"
strQueryResult = myScope.ReadString
pass the value across the bus to the controller and place it in the variable
strQueryResult.
Infinity
Representation
The representation of infinity is +9.9E+37. This is also the value returned when a
measurement cannot be made.
Read Query Results Before Sending Another Command. Sending another command or query
before reading the result of a query clears the output buffer (the current response) and places
a Query INTERRUPTED error in the error queue.
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