A method for determining an artery location on a living subject's skin and positioning a tonometry pressure sensor on the artery location for tonometric blood pressure measurement is provided. The method comprises a non-contact optical search followed by a contact pressure search. In the non-contact optical search, an optical-sensing unit is used to scan the skin along a scan path while maintaining a pre-determined distance between the unit and the scan path. A search region within the scan path and a height profile characterizing the scan path's curvature are determined. The search region is determined such that an artery is predicted to lie thereunder. The artery location is then searched within the search region by the contact pressure search, in which the pressure sensor sweeps along the search region and the sweeping is guided by curvature information provided by the height profile. A device using the method is also provided.