A common problem when setting up communication with the Keithley 2400 is setting the correct communication parameters:
RS-232 (COM port)
When using RS-232 (COM port), you must select the right baudrate and terminator character. Go to Menu → Communication → RS-232.
The default values supported by this Device Class are baudrate 9600 and terminator ‘\r’ (CR). Keithley has a video tutorial on how to set up the communication:
If different programs connect to your SMU and you cannot change these settings, you can use the Port Manager of SweepMe! to define custom port settings.
Warning: Do not change the settings in the Device Class Python file of the SweepMe! driver, as they will be overwritten when the driver receives an update.