Four-point probe

A four-point probe is a measurement tool used to determine a material's electrical conductivity or resistance. It involves placing four small, equally spaced tips onto a material's surface. The two outer tips send a controlled current through the material, while the two inner tips measure the voltage drop. This setup minimizes the effects of contact resistance, allowing for an accurate calculation of how well the material conducts electricity. It's commonly used in research and industry to evaluate the properties of semiconductors, thin films, and other conductive materials.