Keithley 6430 Instruction Manual page 497

-420, "Query UNTERMINATED"
This error occurs when you address the instrument to talk, and there is no response message
to send. The most likely causes are:
• Not sending a query. You must send a valid query to the instrument before addressing it
to talk.
• Sending an invalid query. If you have sent a query and still get this error, make sure that
the instrument is processing the query without error. For example, sending an ill-
formed query that generates an error -113, "Undefined header" and then addressing the
instrument to talk will generate an error -420, "Query UNTERMINATED" as well.
• Valid query following an invalid command. This situation can occur when you send
multiple commands or queries (program message units) within one command string
(program message). When the Model 6430 detects an error in a program message unit,
it discards all further program message units until the end of the string; for example:
:SENS:DATE?; :SENS:FUNC?
In the above program message, the program message unit :SENS:DATE? will generate
error -113, "Undefined header," and the Model 6430 wi|| discard the second program
message unit :SENS:FUNC? even though it is a valid query.
Status and Error Messages B-9