Zeta potential measurements are made using a technique called micro electrophoresis. The measurement is very direct. First, your sample is placed in a viewing chamber called an electrophoresis cell. Then an electric field is activated. This causes the colloids to move with a velocity that is proportional to their zeta potential, and in a direction that indicates whether their charge is positive or negative.
Colloids are comfortably observed and tracked using video optics or a high quality stereo microscope. Once your sample is in the cell, you get your first results in a matter of seconds, and complete results in minutes.