Hello Guy04,
The default value of Waveform Coupling is DC coupling. I am curious to know what version of NI-DMM are you using? I ask this because I am looking at the currently shipping version (NI-DMM 2.6) and the information about the default value of is there in the function/vi reference and the property/attribute reference. I am attaching a snapshot of the help file of at least one place where I found the information.
Regards.
Regrads,
Sead Suskic
National Instruments