| 摘要 |
The method electromagnetically measures a pipe inner diameter ID and a pipe ratio of magnetic permeability to electrical conductivity ~2/.sigma.2 by mea ns of a measuring arrangement 1 comprising a transmitter coil 2 and a receiver coil 3, both coils being coaxial to and longitudinally spaced from each othe r, the measuring arrangement 1 being adapted to be positioned into the pipe CS and displaced through the pipe. The method comprises the steps of: a1) exciting the transmitter coil 2 by means of a transmitter current I1, the transmitter current having a first excitation frequency f1, a2) measuring a receiver voltage Vi at the receiver coil 3, a3) determining a transimpedance Vi/li between the transmitter coil 2 and the receiver coil 3 based on the transmitter current Ii and the receiver voltage V1, and determining a measurement ratio Mi based on said transimpedance, b) repeating the excitati on step a1), the measuring step a2), the transimpedance and the measurement rat io determination step a3) for at least a second excitation frequency f2 so as t o define a measurement ratio vector [M1, M2, ... Mn], c) calculating a prediction function vector [G1, G2, ... Gn] based on the first and at least the second excitation frequency, a plurality of potential pipe ratio of magnetic permeability to electrical conductivity and a plurality of potentia l pipe inner diameter ID, and d) applying a minimizing algorithm onto the measurement ratio vector [M1, M2, ... Mn] and the prediction function vector [G1, G2, ... Gn] and determining the pipe inner diameter and the pipe ratio of magnetic permeability to electrical conductivity corresponding to a maximum solution of the algorithm.
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