More About Oscilloscope Commands 39
Agilent InfiniiVision 3000 X-Series Oscilloscopes Programmer's Guide 1145
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
Agilent 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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