About Creating SAC file

I'm trying to create SAC files by mksac function by François Beauducel. The default unit of the function is velocity, but I need to use acceleration. So I need to modify the header of data unit, which is "IDEP" according to IRIS. Here is my question, I'm not sure what kind of input I should give to this header(IDEP). The following is my code.

   mksac([pwd,'\SACfile\',filenamev],Av,0,'NPTS',length(Av),...
            'DELTA',dt,'KSTNM',station_name,'KCMPNM','Z','CMPINC',0,...
            'STLA',slat,'STLO',slon,'STEL',selv,'EVLA',elat,'EVLO',elon,...
            'MAG',MAG,'LEVEN',true,'IDEP','IACC')