A field-portable impedance reader, configured to measure a resonant impedance response of a resonant sensor, and to be inductively coupled to the resonant sensor, the reader comprising: a reader antenna, and the field-portable impedance reader being characterized in that: the field-portable impedance reader includes a calibrator comprising calibration standards having reference impedance values and a a switch for said calibration standards; wherein the field-portable impedance reader is configured to perform self-calibration by measuring the impedance response of the sensor, comparing the impedance response to said reference impedance values, and extracting equivalent circuit parameters of the sensor; and wherein the field-portable impedance reader further includes: an impedance compensator operatively coupled to the reader antenna, in which the impedance compensator is configured to match the impedance of the calibrator to the combined impedance of the resonant sensor and the reader antenna; a synchronous sampler comprising a digital direct synthesizer, DDS, configured to generate frequency signals acting as excitation signals for the reader antenna so as to generate a magnetic field to interact with the resonant sensor, in which the DDS is configured to be swept over a desired frequency range, and the synchronous sampler is also configured to generate reference signals acting as excitation signals for the calibrator and to receive reference impedance values from the calibrator; and a digital processor coupled to the synchronous sampler, in which the digital processor is configured to receive and process signals from the synchronous sampler. a reader antenna, and the field-portable impedance reader being characterized in that: the field-portable impedance reader includes a calibrator comprising calibration standards having reference impedance values and a a switch for said calibration standards; wherein the field-portable impedance reader is configured to perform self-calibration by measuring the impedance response of the sensor, comparing the impedance response to said reference impedance values, and extracting equivalent circuit parameters of the sensor; and wherein the field-portable impedance reader further includes: an impedance compensator operatively coupled to the reader antenna, in which the impedance compensator is configured to match the impedance of the calibrator to the combined impedance of the resonant sensor and the reader antenna; a synchronous sampler comprising a digital direct synthesizer, DDS, configured to generate frequency signals acting as excitation signals for the reader antenna so as to generate a magnetic field to interact with the resonant sensor, in which the DDS is configured to be swept over a desired frequency range, and the synchronous sampler is also configured to generate reference signals acting as excitation signals for the calibrator and to receive reference impedance values from the calibrator; and a digital processor coupled to the synchronous sampler, in which the digital processor is configured to receive and process signals from the synchronous sampler. the field-portable impedance reader includes a calibrator comprising calibration standards having reference impedance values and a a switch for said calibration standards; wherein the field-portable impedance reader is configured to perform self-calibration by measuring the impedance response of the sensor, comparing the impedance response to said reference impedance values, and extracting equivalent circuit parameters of the sensor; and wherein the field-portable impedance reader further includes: an impedance compensator operatively coupled to the reader antenna, in which the impedance compensator is configured to match the impedance of the calibrator to the combined impedance of the resonant sensor and the reader antenna; a synchronous sampler comprising a digital direct synthesizer, DDS, configured to generate frequency signals acting as excitation signals for the reader antenna so as to generate a magnetic field to interact with the resonant sensor, in which the DDS is configured to be swept over a desired frequency range, and the synchronous sampler is also configured to generate reference signals acting as excitation signals for the calibrator and to receive reference impedance values from the calibrator; and a digital processor coupled to the synchronous sampler, in which the digital processor is configured to receive and process signals from the synchronous sampler. an impedance compensator operatively coupled to the reader antenna, in which the impedance compensator is configured to match the impedance of the calibrator to the combined impedance of the resonant sensor and the reader antenna; a synchronous sampler comprising a digital direct synthesizer, DDS, configured to generate frequency signals acting as excitation signals for the reader antenna so as to generate a magnetic field to interact with the resonant sensor, in which the DDS is configured to be swept over a desired frequency range, and the synchronous sampler is also configured to generate reference signals acting as excitation signals for the calibrator and to receive reference impedance values from the calibrator; and a digital processor coupled to the synchronous sampler, in which the digital processor is configured to receive and process signals from the synchronous sampler.