Cross Device User ID

Hi,

There are any form to detect Cross Device User ID detection? I checked that if I detect an user by User ID but they access in less thant 30 min all their visits is added at first visit as Unique Visitor and all pages visited as Visits so I cannot know the differents device or browsers from the visito acces to my site (always if the visitor browser from different device in less of 30 min).

Thanks

Rubén