Ruud, Thank you for contacting National Instruments.
The problem does in fact have to do with the very small values of Y. As you mentioned, the solution is to scale the Y values, perhaps by multiplying them by 10^+8. The following link will take you to a knowledge base article that will give you more information: http://digital.ni.com/public.nsf/websearch/6F23B120B7A2C585862566F700130A0A?OpenDocument Hope this helps! Matthew C Applications Engineer National Instruments
