Abstract: The sheet resistance of an integrated circuit wafer (W) may be measured during an integrated circuit fabrication process step. A chamber (26) has disposed therein a plurality of probes (40) each having a conductive tip (84) for abutting the work surface at a respective preselected location thereon. A current source (52, 114) is connected by at least two conductors (118, 112) between at least two of the tips (110, 116). A voltmeter (50) is connected between at least two of the tips (120, 126) by further conductors (122, 124). The voltmeter (50) is read out while the process step is being performed, and the voltage is converted to a sheet resistance according to the preselected electrical configuration of the circuit and a predetermined formula.