Contact Profilometers have a stylus which is run across the surface. The profilometers can measure variations in height from a few nanometers to 1 millimeter. The stylus generates an analog signal, which is subsequently converted to a digital signal and saved. Contact Profilometers are considered to be more accurate as they physically touch the surface they are measuring.
Non-contact profilometers These profilometers work without physically coming in contact with the surface. They use laser based techniques.