Detection coil independent frequency domain measurements for an inductively coupled resonant magnetoelastic bending sensor

Inductively coupled resonant sensors (ICR) are a class of wireless, passive sensors which can be used to monitor environmental parameters. Thereby a measurand alters the sensor resonance frequency through an inductance, capacitance and/or resistance change. When performing frequency domain measurements with a detection coil its parasitic capacitance and coupling factor influence onto the evaluated sensor resonance frequency are usually neglected, which leads to an additional measurement uncertainty. Analytical circuit analysis shows, that the transformed sensor impedance can be extracted from the detection coil frequency response function by a calibration scheme, which removes this influence and provides the true sensor resonance frequency. This technique allows a detection coil to be tuned to the sensor resonance frequency, increasing the detection range. By evaluating multiple frequency response characteristics additional sensor parameters can be estimated, such as its resistance, mutual inductance and either inductance or capacitance by providing one a priori known static quantity.