The available COM ports listed in the COM Port drop-down menu are supplied to PC400 by the Windows Operating System (OS). If there are no COM ports shown for selection, it most likely means that there are no COM ports registered with the Windows OS. This can be confirmed using the Windows Device Manager (Control Panel | Device Manager | Ports).
Most modern laptops are not equipped with native RS-232 COM ports. In this situation, a USB-to-RS-232 adapter cable must be used to connect to the data logger. Even when the drivers for this device have been properly installed, the derived COM port will not be shown for selection until the cable is attached to the laptop.