B&K Precision MDL Series - Programming Manual - Manual (Page 21)

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Note: Each command word must be in long-form or short-form, and not something in between. For
example, :SYSTe:PRESe is illegal and will generate an error. The command will not be executed.
Using Queries
Observe the following precautions with queries:
• Set up the proper number of variables for the returned data. For example, if you are reading
back a measurement array, you must dimension the array according to the number of
measurements that you have placed in the measurement buffer.
• Read back all the results of a query before sending another command to the electronic load.
Otherwise a Query Interrupted error will occur and the unreturned data will be lost.
2.2 Types of SCPI Messages
There are two types of SCPI messages, program and response.
1) A program message consists of one or more properly formatted SCPI commands sent from
the controller to the electronic load. The message, which may be sent at any time, requests
the electronic load to perform some action.
2) A response message consists of data in a specific SCPI format sent from the electronic load
to the controller. The electronic load sends the message only when commanded by a
program message called a "query."
The following figure illustrates SCPI message structure:
Figure 5 - SCPI Message Structure