This manual collinear four-point probe station is a simple set up used to measure resistivity of a conductive thin film or a diffusion layer on an insulating material (i.e. silicon dioxide). The system passes a known current through the outer most probes while measuring the voltage drop on the inner two probes. For thin samples (with respect to the probe spacing), these values of current and voltage can be used to estimate the sheet resistance of the thin film.
This measurement works best with blank substrates with continuous films. If the conductive film is patterned it may not permit all four probes to contact the film. Additionally, this measurement is considered to be destructive as it will leave four indentation marks on the film.