When connecting the DA100 and PC (DAQ32) using an RS-232C cable, is there a way to change the communication speed from 9600 bps to 38400 bps?

Yes. If you are monitoring or recording with DAQ32, stop those.
Then, change the speed as follows.

1. Start "Environment, diagnosis and calibration", and click the Environment tab.
2. In the RS-232C field, click 9600 under Baud Rate to display a list. On the list, click 38400.
3. The 3 horizontally displayed dip switches change.
4. This display shows you the dip switch settings you need to make on the DA100's RS-232C module. Turn OFF the power to the DA100 and set the switches.
5. Turn the power to the DA100 back ON. Exit DAQ32, then restart it.
6. 38400 bps communication is now possible.