A calibration system includes an excitation module that introduces an excitation signal to a primary coil of a differential transformer, a measurement module that measures, at a first phase shift, a positive value of an induced signal. The induced signal is caused by the excitation signal on a secondary coil of the differential transformer. The system further includes a calculation module that compares the positive value to a last positive value to form a compared positive value, and a calibration module that changes the first phase shift based on the compared positive value.

A susceptometer includes: a substrate; a plurality of electrodes including: a first pair of electrodes disposed on the substrate; a second pair of electrodes disposed on the substrate, the second pair of electrodes arranged collinear with the first pair of electrodes to form a set of aligned electrodes; and a third pair of electrodes disposed on the substrate, the third pair of electrodes arranged noncollinearly with set of aligned electrodes; and a solenoid circumscribingly disposed around the electrodes to: receive the sample such that the solenoid is circumscribingly disposed around the sample; receive an alternating current and produce an primary magnetic field based on the alternating current; and subject the sample to the primary magnetic field.

An object of this invention is to sense a transient displacement of the blade position to thereby detect abnormalities early. The invention includes: one or more first sensors mounted so as to be removable from an outer surface of a casing opposed to blade tips; a second sensor for acquiring a signal from a fixed point on a rotor shaft of the blades; a section configured to extract data groups from an output signal of the first sensor on the basis of information acquired by the second sensor; a section configured to average the data groups; a section configured to determine thresholds from averaged data obtained under a healthy condition; and an assessing section configured to compare magnitude of the thresholds and sensor signals obtained during blade status monitoring. Since a transient displacement of blade position can be sensed, abnormalities can be detected early in this invention. This early detection, in turn, enables a rotation to be stopped during an initial phase of blade damage. The invention is therefore advantageous in minimizing impacts on other devices.