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Chapter 2, Methods For Reading Measurement Results
Background
This situation can be avoided entirely by:
1. sending a Selected Device Clear (SDC) interface message to put the Test Set’s GPIB
subsystem into a known state.
2. sending a command to terminate the requested measurement cycle.
These commands issued in this order will allow the control program to regain
control of the Test Set. Any other sequence of commands will result in unexpected
operation.
The following programs demonstrate a recommended technique for querying and
entering data from the Test Set. This technique will prevent the Test Set from
getting into a ‘hung’ state such that power must be cycled on the Test Set to regain
manual or programmatic control.
There are a variety of programming constructs which can be used to implement
this technique. In the programming examples presented, a function call is
implemented which returns a numeric measurement result. The function call has
two pass parameters; the query command (passed as a quoted string) and a time-
out value (passed as a integer number).
The time-out value represents how long you want to wait, in seconds, for the Test
Set to return a valid measurement result. If a valid measurement result is not
returned by the Test Set within the time-out value, the function returns a very large
number. The calling program can check the value and take appropriate action.
The program examples are written so as to be self-explanatory. In practice, the
length of: variable names, line labels, function names, etc., will be
implementation dependent.