Patent ID: 8451007

Claim:
An input circuit for the inductive measurement of the electrical conductivity of a fluid medium connected by a measurement terminal to a sensor, the sensor includes an excitation coil for applying an excitation current to the fluid medium and an induction coil for receiving an inducted current generated by the excitation current via the fluid medium, said input circuit comprising: a control circuit having a first input and a first output, the first input receiving a signal corresponding to the induced current from the measurement terminal connected thereto, the first output connected to a first feedback loop to provide a first output signal, the first output signal is a compensation current partially compensating for the induced current, the control circuit further comprising: a second output providing a second output signal corresponding to the electrical conductivity of the fluid medium; and a second feedback loop connecting the second output of the control circuit to a second input of the control circuit to provide a second input signal corresponding to the second output signal, wherein the control circuit is configured to control the first output signal and the second output signal such that the second and first input signals remain substantially equal.