A novel inductance sensor for control rod position with high-precision and continuous measurement

Conventional inductance control rod position measurement sensors (ICRPMS) still suffer from insufficient measurement accuracy and the inability to achieve continuous measurement, which seriously affects reactor safety. Thus, a novel ICRPMS based on a segmented coil structure is proposed in this paper. To investigate the factors influencing the output characteristics of the sensor, an analytical model with a driving rod based on the truncated region eigenfunction expansion (TREE) method is established, and the feasibility of the model is verified by simulation and experiments, showing relative errors of less than 6.2% and 6.7%, respectively. Subsequently, to enhance integration of the measurement system, a single-phase inverter circuit is designed as the excitation source, ensuring a stable sinusoidal output voltage. Finally, the precision is evaluated under cold and thermal states. Experimental results indicate that the maximum error of the sensor in continuous measurement mode is within 2 mm, and the maximum nonlinearity error is less than 1.2% over the full 320 mm stroke without compensation.