Abstract: The scanning probe microscope has a primary control loop (7, 11, 12) for keeping the phase and/or amplitude of deflection at constant values as well as a secondary control loop (9) that e.g. keeps the frequency of the cantilever oscillation constant by applying a suitable DC voltage to the probe while, at the same time, a conservative AC excitation is applied thereto. By actively controlling the frequency with the first control loop (7, 11, 12) and subsequently controlling the DC voltage in order to keep the frequency constant, a fast system is created that allows to determine the contact potential difference or a related property of the sample (3) quickly.

Abstract: To increase the accuracy and resolution of an m bit digital analog converter, n bit input values with n>m are fed to a control circuit and converted to a series of control values for the digital analog converter using dithering techniques. When the series of control values straddles a major transition where a large number of bits are switched between 1 and 0, a corrected series of control values is retrieved from a calibration table. The corrected series takes into account the glitch effects observed at the output of digital analog converter at a major transition.