HP 3468A - Page 70

Since you know the voltage to be measured is small, set the 3468A to a low
range before we autorange. The instruction “R2” will do this. Furthermore, if we
want the meter to only take one reading, add the instruction “T2” to the end of
the string. By adding it at the end, the meter is set up for the measurement before
the reading is actually triggered. The complete string, along with the OUTPUT
statement is:
OUTPUT 901; ”F2R1RAZ1N4T2”
Instructions are implemented as they are received through the loop. In other
words, the 3468A will go to the ac volts mode before it goes to the lowest
range. It will go to the lowest range before autorange, etc. The last thing it will do
is trigger for the measurement.
Programming Hints
When more than one command is sent to the 3468A in one “OUTPUT” instruc-
tion statement, the commands are executed as they arrive. Therefore it is best to
make the trigger statement the last statement in the command string so that the
3468A will be set up for the measurement before it triggers. If you send the com-
mand ”T2T1”, the “T1” command is the last one received and will be in effect.
Instructions are sent to the 3468A as a series of 8-bit ASCII characters. All lower-
case letters, spaces, commas, semicolons, Carriage Return (CR) and Line Feed (LF)
are ignored and may be freely used to format commands for easy readability. All
null characters, form feed, and vertical and horizontal tab characters result in a
syntax errror. All other characters and sequences not explicitly allowed (see the
Command Table) also result in a syntax error. Errors will be discussed later. For
example, sending the message:
OUTPUT 901;”Function 1 Range 1”
would be the same as:
OUTPUT 901;”F1R1”
When a multicharacter command is received, if a character is received which does
not fit into the syntax of the command, the command will be aborted and an error
will be generated. An attempt is made to process the character as if it were the
first character of another command. For example, the command “FR3” will cause
a syntax error but then go on to range 3 (that is, ”“R3”).
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