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This paper presents a Fiber Bragg Grating (FBG)-based torque sensor with high sensitivity and miniature size for MIS instruments and multi-finger hands. The proposed sensor design mainly consists of a torque-sensitive flexure structure and two diagonally arranged optical fibers embedded with FBG sensing elements. An improved hollow hexaform structure with flexible hinges has been utilized to design the torque-sensitive flexure with an excellent linear measurement range and a solid capacity to resist non-torsion loading. Two optical fibers with an FBG inscribed each adopt a two-point gluing configuration with a tightly stretched status, and they are arranged diagonally along the hyperboloid surface. This configuration can obtain improved sensitivity and resolution and avoid the drawbacks of FBG chirping and low repeatability. Finite element modeling (FEM)-enabled simulation has been implemented to perform design optimization for further sensor sensitivity improvement and performance investigation. The prototyped sensor has been calibrated and achieves a high resolution of 0.062N $\cdot $ mm within [−100, 100N $\cdot $ mm] and excellent linearity with a small linearity error of 0.68%. The crosstalk experiments on the bending moment of Mx and My and the axial force have been conducted to validate the anti-interference capacity on the basis of the small values of 0.47%, 0.31%, and 1.78%. The proposed design also supports convenient customization to achieve the adjustable measuring range and torque sensitivity, which has been validated by another sensor version with a resolution of 0.26 $\text{N}\cdot $ mm within [−500, 500N $\cdot $ mm].

Overhauser magnetometer, a kind of static-magnetic measurement system based on the Overhauser effect, has been widely used in archaeological exploration, mineral resources exploration, oil and gas basin structure detection, prediction of engineering exploration environment, earthquakes and volcanic eruotions, object magnetic measurement and underground buried booty exploration. Overhauser magnetometer plays an important role in the application of magnetic field measurement for its characteristics of small size, low power consumption and high sensitivity. This paper researches the design and the application of the analog circuit of JOM-3 Overhauser magnetometer. First, the Larmor signal output by the probe is very weak. In order to obtain the signal with high signal to noise rstio(SNR), the design of pre-amplifier circuit is the key to improve the quality of the system signal. Second, in this paper, the effectual step which could improve the frequency characters of bandpass filter amplifier circuit were put forward, and theoretical analysis was made for it. Third, the shaping circuit shapes the amplified sine signal into a square wave signal which is suitable for detecting the rising edge. Fourth, this design elaborated the optimized choice of tuning circuit, so the measurement range of the magnetic field can be covered. Last, integrated analog circuit testing system was formed to detect waveform of each module. By calculating the standard deviation, the sensitivity of the improved Overhauser magnetometer is 0.047nT for Earth’s magnetic field observation. Experimental results show that the new magnetometer is sensitive to earth field measurement.

Overhauser magnetometer is a detection instrument of the geomagnetic field. The sensitivity of Overhauser magnetometer is one of the important technical parameters. This paper introduces a high sensitivity and low power consumption JOM-2 Overhauser magnetometer based on Overhauser effect. A detailed description of the system controlled by DSP+CPLD is provided from three aspects: design principle, system composition and the sensitivity experimental test. In order to explore the sensitivity of JOM-2 under ideal and practical conditions, we give the test methods and results. Under ideal conditions, we use a DDS function signal generator to make a static magnetic field whose frequency and amplitude are constant and the signal to noise ratio (SNR) is high. And we use an analog function signal generator to generate a time-dependent magnetic field. These experimental results indicate that the ideal sensitivity of the JOM-2 Overhauser magnetometer is up to 0.003nT. Under practical conditions, the sensitivity can reach 0.043nT, which confirms that the JOM-2 Overhauser magnetometer is sensitive to geomagnetic field measurement.

Overhauser proton magnetometer is a scalar instrument for measuring the total magnetic field intensity. Sensitivity, as one of the important specifications, reflects the ability to measure the change of magnetic field when detecting magnetic anomalies. It is very important to study the sensitivity estimation method for accurately evaluating the sensitivity specification of the magnetometer. In this paper, two methods, synchronous measurement method and gradient measurement method, are proposed to estimate the instrument sensitivity. The experimental results show that the lower the external environmental electromagnetic interference is, the more accurate the sensitivity estimation is. Furthermore, when the synchronization accuracy is about 1.7 milliseconds, the estimation results of the synchronization measurement method and the gradient measurement method are almost equal. Finally, in the environment with low electromagnetic interference, the sensitivity estimation of the JOM-4 magnetometers is 0.042 nT@3s.