Magnetic nanoparticles (MNPs) are commonly used in biomedical detection due to their capability to bind with some specific antibodies. Quantification of biological entities could be realized by measuring the magnetic response of MNPs after the binding process. This paper presents a contactless scanning prototype based on tunneling magnetoresistance (TMR) sensors for quantification of MNPs present in lateral flow strips (LFSs). The sensing unit of the prototype composes of two active TMR elements, which are parallel and closely arranged to form a differential sensing configuration in a perpendicular magnetic field. Geometrical parameters of the configuration are optimized according to theoretical analysis of the stray magnetic field produced by the test line (T-line) while strips being scanned. A brief description of our prototype and the sample preparation is presented. Experimental results show that the prototype exhibits the performance of high sensitivity and strong anti-interference ability. Meanwhile, the detection speed has been improved compared with existing similar techniques. The proposed prototype demonstrates a good sensitivity for detecting samples containing human chorionic gonadotropin (hCG) at a concentration of 25 mIU/mL. The T-line produced by the sample with low concentration is almost beyond the visual limit and produces a maximum stray magnetic field some 0.247 mOe at the sensor in the x direction.

This paper introduces the design and development of an ultrasonic pig used for submarine oil pipeline corrosion inspection. Structure and functions of the equipment, as well as ultrasonic data acquisition system and off-line signal processing method are presented. The pig adopts a train-like structure including driver cups, batteries, ultrasonic transducers and data acquisition unit, which can detect and locate the corrosion of inspected pipeline. The data acquisition system is designed based on a digital signal processor and field programmable gate arrays structure to sample, process and compress the ultrasonic data and then store them in a hard disk. The off-line signal analysis method adopts a non-phase delay peak extraction algorithm to accurately calculate the pipe wall thickness. According to the thickness of each detected point, an ultrasonic image is traced by false color image, and then the potential defects are recognized by using a 3 × 3 grids template and classified according to American Petroleum Institute Standard. Both experimental and engineering testing results show that the pig is of perfect performance and could inspect defects greater than 10 × 10 mm² successfully.

Torque measurement presents challenges particularly in rotating structures, where traditional measurement methods are often limited. Surface Acoustic Wave (SAW) sensors, with their inherent wireless and passive characteristics, possess unique advantages in mechanical measurements of rotating structures. Currently, most of the existing resonant SAW mechanical sensors suffer from issues of short reading distances or poor signal quality, primarily due to the difficulty in achieving high Q factor of SAW resonators. Additionally, the problem of high temperature coefficient generally exists in the field of SAW sensors, which will seriously interfere with the measurement accuracy of the sensors. In this paper, a SAW torque sensor with excellent wireless performance was proposed based on the X-112°Y LiTaO3 substrate due to its large electromechanical coupling coefficient (K²) and favourable temperature characteristics. We investigated and simulated the characteristics of the sensing element including strain sensitivity, temperature coefficient, Q factor and electromechanical coupling coefficient, and designed SAW resonators on X-112°Y LiTaO₃ substrates. The experimental results show that the proposed SAW sensor has higher signal-to-noise ratio echo signal quality at the same wireless measurement distance compared with the case traditional high Q factor SAW sensor based on quartz substrate. Moreover, from temperature tests, the proposed SAW sensor has a linear temperature effect, which is beneficial to the compensation of temperature drift. Based on the manufactured SAW sensors, a SAW torque measurement system with wonderful linearity, repeatability and hysteresis was developed. Our work provides a valuable and promising solution for wireless and passive measurement of mechanical quantities.

The finite element method (FEM) has been applied to extract the coupling-of-modes (COM) parameters of surface acoustic wave (SAW) devices for a long time. It always involves calculating the dispersive curves or harmonic admittance, which makes the extraction process and results sophisticated, time-consuming and inaccurate. Therefore, a simple method is proposed to extract all COM parameters of the SAW devices rapidly and accurately in this paper. It is based on the FEM and combines the stationary analysis with modal analysis. We have described in detail the basic principles and procedures of the proposed method, and made a comprehensive comparison between the proposed method and the other two existing methods. We have also examined the proposed method by extracting COM parameters of some common SAW substrate, and compared our extracted results with those reported in the other literatures. Results show that our proposed method holds higher accuracy and more efficiency (~s order) than the others (~h order). Moreover, our extracted COM parameters are in an excellent agreement with those reported in the other literatures.

This paper presents a method of health monitoring for coated steel belts in an elevator system by measuring the electrical resistance of the ropes embedded in the belt. A model on resistance change caused by fretting wear and stress fatigue has been established. Temperature and reciprocating cycles are also taken into consideration when determining the potential strength degradation of the belts. It is proved by experiments that the method could effectively estimate the health degradation of the most dangerous section as well as other ones along the whole belts.

This paper presents a passive wireless weighing sensor based on surface acoustic wave (SAW) technology. It consists of a one port SAW sensing resonator and force sensitive structure. ST-cut quartz was employed as the piezoelectric substrate of the SAW sensing resonator, and the sensing characteristics of the SAW sensitive resonator were simulated by the finite element method (FEM). The double-connected holes structure was proposed to form difference sensing unit, which improves the sensitivity of the sensor and can counteract the effects of ambient temperature. Based on the designed force sensitive structure and SAW sensing resonator, a wireless passive SAW weighing test platform was built and tested. The experimental result shows that the sensor is consistent with the design expectation. The sensitivity of the weighing sensor is 75.35kHz/kg, and the nonlinear error is 0.17%. Under consecutive loading and unloading of 0-5kg, the hysteresis is 1.1%, and the maximum standard deviation of repeatability under the same load is 2.277kHz (about 0.6% of the full scale frequency shift). The difference structure effectively improves the sensitivity, and has a good ambient temperature inhibition effect. Under temperature of 30°C-60°C, the frequency shift is within 3kHz, which is 0.8% of the full scale.