How to connect from IGOR PRO 7 on MacBook Pro (USB-C) to Mettler-Toledo balance (RS232)

We try to connect a balance from Mettler-Toledo to the MacBook under Sierra.
connection USB-C tp USB2 to RS232 on balance.
Parameters on balance and IGOR VDT2 XOP set equivalent.
I can see only the following ports:
>print S_VDT
lpss-serial1;lpss-serial2;Bluetooth-Incoming-Port;

Under 'System Report' one can recognise the adapters but not the balance.

Maybe a hint could be that the balance allows only for characters ANSI/WIN or IBM/DOS and nothing like that can be set in the VDT2 settings.