Right click on your control and select Representation >> Double
Precision. A Double-precision floating-point number takes 64 bits of
storage on disk.
Take a look at this <a
href=http://digital.ni.com/public.nsf/websearch/C261612DFCA8BD3586256CC300713EA6?OpenDocument>link</a>.
Hope this helps!
S Vences
Applications Engineer
National Instruments