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A novel contactless method for conductivity sensing is introduced that utilizes a driving coil and two tunable and near resonant coils. The design uses only inexpensive electronic components and a variable frequency rf generator. An algebraic expression for the response has been derived and simulations indicate a linear response to surface conductivity changes over at least four orders of magnitude. The sensitivity is shown to depend on the conductivity of the substrate, with a limit to conductivity changes as low as 10-4 Ω-1 for insulating substrates. An ultrahigh vacuum compatible version of this probe has been used to monitor in situ aluminum thin film growth by chemical vapor deposition on a native oxide covered, highly doped, Si(111) wafer. On this semiconducting substrate (3 Ω-1) a sensitivity to sheet conductivity changes as low as ∼2×10-2 Ω-1 has been demonstrated. The Al films show a discrete jump in differential sheet conductivity associated with Al cluster coalescence during growth. © 1997 American Institute of Physics.