Design of compensation coils for EMI suppression in magnetostrictive linear position sensors

Induced Voltage Linear Extraction Method Using an Active Kelvin Bridge for Disturbing Force Self-Sensing

This paper presents an induced voltage linear extraction method for disturbing force self-sensing in the application of giant magnetostrictive actuators (GMAs). In this method, a Kelvin bridge combined with an active device is constructed instead of a conventional Wheatstone bridge for extraction of the induced voltage, and an additional GMA is adopted as a reference actuator in the self-sensing circuit in order to balance the circuit bridge. The linear fitting of the measurement data is done according to the linear relationship between the disturbing forces and the integral of the induced voltage. The experimental results confirm the good performance of the proposed method, and the self-sensitivity of the disturbing forces is better than 2.0 (mV·s)/N.

Implementation of High-Precision Magnetostrictive-Type Liquid Level Measurement System UsingWavelet Transform

Precise measurement of levels of liquids stored in tanks is essential for monitoring and predicting disasters by detecting leakages or arbitrary discharge of toxic materials. Therefore, tanks are typically equipped with a series of liquid level sensors. A magnetostrictive-type level sensor is composed of a waveguide, a current pulse interrogator, and a sensing coil for detecting reflective torsional signals caused by Wiedemann effect, which is themain principle of operation of magnetostrictive-type liquid level sensors. In order to implement a high-precision magnetostrictivetype liquid level measurement system, we used time–frequency analysis techniques such as wavelet transform (WT) to precisely detect the reflected signals. By using time–frequency analysis techniques such as short-time Fourier transform (STFT) and WT, a robust and precise liquid level measurement system can be implemented even in noisy environments.

High resolution switching mode inductance-to-frequency converter with temperature compensation

This article proposes a novel method for the temperature-compensated inductance-to-frequency converter with a single quartz crystal oscillating in the switching oscillating circuit to achieve better temperature stability of the converter. The novelty of this method lies in the switching-mode converter, the use of additionally connected impedances in parallel to the shunt capacitances of the quartz crystal, and two inductances in series to the quartz crystal. This brings a considerable reduction of the temperature influence of AT-cut crystal frequency change in the temperature range between 10 and 40 °C. The oscillator switching method and the switching impedances connected to the quartz crystal do not only compensate for the crystal's natural temperature characteristics but also any other influences on the crystal such as ageing as well as from other oscillating circuit elements. In addition, the method also improves frequency sensitivity in inductance measurements. The experimental results show that through high temperature compensation improvement of the quartz crystal characteristics, this switching method theoretically enables a 2 pH resolution. It converts inductance to frequency in the range of 85-100 µH to 2-560 kHz.