Andreas,
If you go to the main NI Developer Exchange page (www.ni.com/exchange) and search for "bt848", you will find another message thread discussing this very issue. They offer a few good suggestions in this thread. You could also contact the individuals who were involved in that thread if you need more information.
I hope this suggestion helps. Have a pleasant day.
Sincerely,
Darren Nattinger
Applications Engineer
National Instruments
