Patent ID: 8536883

Claim:
A method of measuring the permittivity and/or conductivity of a multiphase fluid flowing through a conduit, the method comprising measuring the signal from a first electromagnetic transmitter to a first electromagnetic receiver separated by a first distance across the conduit, measuring the signal from the first electromagnetic transmitter to a second electromagnetic receiver separated by a second distance across the conduit, measuring the signal from a second electromagnetic transmitter to the first electromagnetic receiver separated by a distance substantially equal to the second distance across the conduit, measuring the signal from the second electromagnetic transmitter to the second electromagnetic receiver separated by a distance substantially equal to the first distance across the conduit, wherein the first and second distances are substantially different and wherein any variation in gain values applied to the transmitters and receivers affects the measurements of signals; using a ratio of the signals received by the first and second receivers from the first transmitter to derive a first measurement of phase shift and amplitude attenuation; using a ratio of the signals received by the first and second receivers from the second transmitter to derive a second measurement of phase shift and amplitude attenuation; and avoiding dependence on gain values by averaging the first and second measurements of phase shift and amplitude attenuation to obtain a measurement of the phase-shift and amplitude attenuation which is independent of the gain values applied to the receivers and transmitters and thereby provide an estimate of the permittivity and/or conductivity of the multiphase fluid.