A plasma diagnostic technique for measuring the electron density, electron temperature, and ion current near a surface in radio frequency (rf) discharges is proposed. The sensor uses a small wire probe to determine the plasma potential and a small metal electrode to measure the current and voltage profiles. The values of current, sheath voltage, and time derivative of sheath voltage at three distinct points during the rf cycle are used in conjunction with an analytical sheath model to determine the plasma parameters. The technique is demonstrated by implementing the diagnostic in a computer model of an inductively coupled plasma reactor which has an rf biased substrate. Although any three disjoint sets of measurements can ideally be used, a sensitivity analysis is used to show that certain sets may be more suitable in experimental systems where noise is present. ©1998 American Institute of Physics.