Samples are usually placed on an RF bias electrode for an inductively coupled plasma device. The RF current and voltage waveforms at the bias electrode were measured. The current through the stray capacitance was cancelled by an LC cancel circuit. Only the sheath impedance at the bias electrode was considered as the equivalent circuit, The RF voltage greatly depended on the RF power, but the RF current slightly depended on the RF power. The conduction current could be related to the plasma density. The incident ion current to the bias electrode was given by the half value of the amplitude of the conduction current. The obtained incident ion current agreed with those obtained from different methods. (c) 2005 Elsevier B.V. All rights reserved.