The magnitude and relative phase of the time varying magnetic field in an inductively coupled discharge have been measured with twodB/dt(B-dot) probes: OneB-dot probe was enclosed by a dielectric tube (as is commonly used indB/dtmeasurements) while the other, a thin wire probe, was immersed directly into the plasma. Each probe was used to measure the radial and axial component ofdB/dt. A comparison of rf electric fields and currents obtained by the two probes showed essentially different results. The disagreement is interpreted to be due to a large local disturbance of the plasma density and current caused by the dielectric tube. ©1997 American Institute of Physics.