CDO

Good morning people.

I'm having a problem when I try to read a netcdf data. I used the CDO to convert an ensemble file ECMWF in grib format (C1E06291200071312001) to netcdf4. However he is reading the members as if they were time steps.
I used the following command to convert:
cdo -f nc copy C1E06291200071312001 test.nc
Results:
cdo copy: Processed 431613 values from 1 variable over 51 timesteps ( 0.06s )

So I open the grads software and use sdfopen command:
ga-> sdfopen test.nc
Scanning self-describing file: test.nc
gadsdf: Time unit has too small an increment (min. 1 minute).

how do I properly convert the data? So the cdo understand that it is an ensemble data?
Thanks.