The first thing you should do:
Look for the selected Interface - press button "Menue"
Then select "Communication" and there "RS-232". Typically these instruments are delivered in "GPIB"-mode - and nothing will happen at serial Interface until you change it !!
Next step: You have to go again into the same Menue and now specify the "RS232-setup"
(baudrate,bits,parity,terminator,flow-ctrl).
Find attached a simple serial vi, how I have tested a K2400-SMU to go into V-mode. Complete sweep programs available; if needed write to: werner.hasche@web.de
regards
wha
P.S. You should select the baudrate etc. like in example program or edit the vi !!!