Four-probe method:

In this method, four probes are utilized to measure the resistance of the samples. For example, two of the outer probes are used to send the current from the source meter and other two inner probes are used to measure the voltage drop across the sample.

The typical set up of the four-probe method is shown in Figure 24.03. There are four equally spaced tungsten metal tips supported by springs at one end to mount the sample surface without any damage.

Figure 24.03: Schematic of four-probe setup.