新型环形同点单铁芯双分量磁通门传感器

双分量磁通门传感器在金属磁记忆检测中得到广泛使用,且使用的双分量磁通门传感器为双铁芯式跑道型设计的磁通门传感器。由于传感器中的双铁芯磁参数不一致、铁芯不闭合的原因,产生变压器效应,形成了测量噪声。双分量磁通门通常由两个磁通门传感器平行放置而成。因此,由于传感器铁芯参数,线圈参数不可能完全一致所造成的传感器之间的一致性差,而且双分量或多分量磁通门传感器存在着几何中心不重合的问题。本文研究设计了新型双分量磁通门传感器,采用环形铁芯设计,直接应用单铁芯调理双方向的磁通门信号,改善了双分量传感器的一致性差、几何中心不同点的问题,有效的抑制了变压器噪声,提高了磁通门传感器的测量中的测量准确度,减少了测量误差。     

Bulk property of 1/f noise for piezoresistive Ni/Cr thin films in pressure sensors on flexible substrate

In the current paper, we report the 1/f noise measurement of nichrome Ni/Cr (80/20 %) thin films for two types of pressure sensors: relative pressure sensors and absolute pressure sensors. The normalized Hooge coefficient for nichrome thin film was found to be 1.89 × 10^?10 for the relative pressure sensors and 4.64 × 10^?11 for the absolute pressure sensors. We demonstrated that the normalized Hooge coefficient multiplied by the volume of the thin film become constant regardless of the sensor types and discuss the complexities arise for the miniaturization of MEMS sensors due to the bulk noise properties of piezoresistive thin films.     

Ultra Dense DNA Microarray Design using Magnetoresistive Detectors

Microelectronic chip-based systems are available for a wide variety of applications. Many of these systems rely on NON-INTEGRATED optical detection schemes to collect data from the chips. A magnetoresistive detection format, however, can be completely integrated. This paper presents some basic concepts for optimizing micron-sized magnetoresistive sensors for single nucleotide polymorphism (SNP) analysis and DNA diagnostics. Magnetoresistive sensors are nano-fabricated thin film resistors whose resistance changes as a function of magnetic field. The magnetic DNA assay replaces the EXTERNAL optical reader apparatus with an INTEGRATED magnetoresistive sensor at each “pixel” of the array. The EXTERNAL light source can be replaced by an INTEGRATED magnetic field generation strap, or by a simple external coil. Magnetoresistive pixel sizes could presently be ˜ 3 microns on a side, and decrease to ˜ 100 nm with technological improvements. It is shown that, taking reasonable values for critical parameters, a signal to noise ratio of 10,000 : 1 is achievable using 10 nm paramagnetic beads as the assay label. As early demonstrations of the feasibility of this system, data have been collected using NVE's magnetoresistive sensors (non-optimized) to easily detect single micron-sized magnetic beads. Presently NVE is working on 1 million bit arrays of magnetoresistive sensors which are being fabricated into magnetoresistive random access memory (MRAM) chips. These arrays have many similarities to what is required for the magnetoresistive DNA assay including sub-micron bit size and single bit addressability.     

Chopping of a weak magnetic field by a saturable magnetic shield

A method for measuring a weak magnetic field with a Hall sensor is described. This method consists of chopping the magnetic field to be measured with a magnetic shield surrounding the Hall sensor. The magnetic shield is periodically driven into saturation by means of an excitation coil. Thus, the Hall device is alternately exposed to/shielded from the d.c. or slowly varying external field to be measured. During the time intervals when the magnetic shield is saturated, the external field passes and is detected by the Hall sensor. When it is not saturated the Hall sensor is shielded from the external field. This chopping method yields a magnetic measurement unaffected by 1/ƒ noise and offset errors of the Hall sensor, therefore improving its detectivity.     

Low-frequency noise in planar Hall effect bridge sensors

The low-frequency characteristics of planar Hall effect bridge sensors are investigated as function of the sensor bias current and the applied magnetic field. The noise spectra reveal a Johnson-like spectrum at high frequencies, and a 1/f-like excess noise spectrum at lower frequencies, with a knee frequency of around 400 Hz. The 1/f-like excess noise can be described by the phenomenological Hooge equation with a Hooge parameter of γ_H = 0.016. The detectivity is shown to depend on the total length, width and thickness of the bridge branches. The detectivity is improved by the square root of the length increase. Moreover, the detectivity is shown to depend on the amplitude of the applied magnetic field, revealing a magnetic origin to part of the 1/f noise.     

Influence of sensor imperfections to electronic compass attitude accuracy

Analysis of various errors of orientation and motion sensors and their influence on resulting compass attitude information are investigated and quantified in this paper. A triple-axis acceleration sensor and a triple-axis magnetic sensor are considered to form a compass module giving full orientation information (attitude). 3D-compass module with PCB-fluxgate sensors and off-shelf acceleration sensor is introduced. Three main sensor error sources are discussed separately and their contribution to final compass heading accuracy is investigated. These are sensor orthogonality error, linearity error and ADC quantization noise. The influence of these errors is simulated on artificial group of test cases which evenly covers various orientations of the compass module. It was found that the errors in the accelerometric system have major influence on the heading accuracy. It was concluded that even low-resolution AD converters may have only a minor influence on the system accuracy, while the dominant error sources are sensor triplet nonorthogonality and sensor non-linearity.     

Ultrasonic sensor data integration and its application to environment perception

To move in an unknown or uncertain environment, a mobile robot must collect information from various sensors and use it to construct a representation of the external world. Ultrasonic sensors can provide range data for this purpose in a simple and cost-effective way. However, most ultrasonic sensors are not sufficient for environment recognition because of their large beam opening angles. In this article the beam-opening-angle problem is solved by fusing data from multiple ultrasonic sensors. We propose two methods for sensor data fusion. One uses an artificial neural network (ANN), and the other is based on a mathematical model. Simulations and experiments show that the mathematical model is more accurate when there is no noise in the sensor readings, but the ANN method is better when the sensors are subject to much noise. To extract line segments from the ultrasonic image, we develop a line extractor that is more efficient than traditional line fitting methods in this application. Experimental results show that this method is effective for environment perception in a robotic system. © 1996 John Wiley & Sons, Inc.     

不同长度敏感元件的两种巨磁阻抗传感器传感性能研究

针对采用Co基非晶丝作为敏感元件的传统巨磁阻抗传感器和非对角巨磁阻抗传感器进行比较研究。改变敏感元件的长度,观察两者在直流外磁场作用下输出信号的变化规律,并讨论退磁场等因素对传感器输出信号的影响。结果显示非对角巨磁阻抗传感器具有高灵敏度,无磁滞等优点,且灵敏度随样品长度的减小略有增大,在测量弱磁场方面表现出更大的潜力,为磁敏传感器的小型化提供了一定的参考依据。     

MEMS micro fluxgate sensors with mutual vertical excitation coils and detection coils

As a classic Earth magnetic field sensor, fluxgate magnetic sensors have great potential applications in many fields. This paper presents a new 3D micro-solenoid fluxgate magnetic sensor based on the MEMS technique. The excitation coils were placed vertically to the detection coils on the chip plane, around a rectangular shaped magnetic core. Polyimide was used to insulate coils and magnetic core. Width of copper conductor lines is 50 μm, and line space is 50 μm. The design of such fluxgate magnetic sensor followed second harmonic signal selecting method. Phase-lock amplifier was used to get second harmonic signal output by detection coils. The linear range of 0–80 μT with sensitivity of 6.7 V/T was achieved from the fabricated sensor with excitation current of 430 mA and the operational frequency of 40 KHz. As the excitation current was 470 mA, linear range of 0–50 μT with sensitivity of 21.7 V/T was achieved.     

Comparison analysis of energy loss between micro clamped–clamped and clamped-free beam in vertical motion flux modulation magnetic sensor

The 1/f noise is one of the main noise sources of giant magnetoresistive sensors, which will cause intrinsic detection limit at low frequency. To suppress this noise, a vertical motion flux modulation (VMFM) integrated with simple microelectromechanical-systems (MEMS) structure is proposed. However, the energy loss of VMFM structure is not considered yet. In this paper, energy loss between MEMS clamped–clamped beam (C–C beam) and clamped-free beam (C-F beam) used as VMFM structure are compared. In this comparison, quality factor (Q) is proposed to characterize the energy loss of the VMFM structure. Theory analysis and experimental results show that quality factor of a C–C beam is higher than that of a C-F beam, indicating a lower energy in VMFM. Finally, the sensitivity of a VMFM magnetic sensor modulated by a C–C beam is tested, and the sensitivity gets 3.85 mV/V/Gs.

     

Magnetic landmark-based position correction technique for mobile robots with hall sensors

We propose a precise position error compensation and low-cost relative localization method in structured environments using magnetic landmarks and hall sensors. The proposed methodology can solve the problem of fine localization as well as global localization by tacking landmarks or by utilizing various patterns of magnetic landmark arrangement. In this paper, we consider two patterns of implanted permanent magnets on the surface, namely, at each vertex of regular triangles or rectangles on a flat surface. We show that the rectangular configuration of the permanent magnetic bars is better for a robust localization under sensor noise. For the experiments, permanent magnet sets in rectangular configuration are placed on the floor as landmarks at regular intervals, and magnetic hall sensors are installed at the bottom of a mobile robot. In our implementation, the accuracy after the error compensation is less than 1 mm in the position and less than 1° in the orientation. Due to the low cost and accuracy of the proposed methodology, it would be one of the practical solutions to the pose error correction of a mobile robot in structured environments.     

低噪声宽频带感应式磁传感器

感应式磁传感器是频率域电磁（FEM）法中使用最广泛的磁传感器,通常由感应线圈和前置放大器组成,其中前置放大电路是影响磁感应式磁传感器性能指标的核心因素。为了增加感应式磁传感器探测深度和微弱磁场信号的能力,要求前置放大电路具有宽频带、低噪声等性能。基于磁通负反馈的原理,设计并研制了斩波前置放大器,有效抑制了感应线圈的输出噪声,使感应线圈谐振频率两侧具有平坦的幅频特性曲线,拓宽了感应式传感器的响应频带。在屏蔽室内对感应式磁传感器的性能指标进行了测试,其频带范围为0.001Hz～10kHz,输入噪声为3.75nVHz（1/2）,为感应式磁传感器在实际中的应用提供了性能保障。     

Assessing the effect of hydrocarbon oil type and thickness on a remote sensing signal: A sensitivity study based on the optical properties of two different oil types and the HYMAP and Quickbird sensors

We measured the light absorption properties of two naturally occurring Australian hydrocarbon oils, a Gippsland light crude oil and a North West Shelf light condensate. Using the results from these measurements in conjunction with estimated sensor environmental noise thresholds, the theoretical minimum limit of detectability of each oil type (as a function of oil thickness) was calculated for both the hyperspectral HYMAP and multispectral Quickbird sensors. The Gippsland crude oil is discernable at layer thickness of 20 µm or more in the Quickbird green channel. The HYMAP sensor was found to be theoretically capable of detecting a layer of Gippsland crude oil with a thickness of 10 µm in approximately six sensor channels. By contrast, the North West Shelf light condensate was not able to be detected by either sensor for any thickness up to 200 µm. Optical remote sensing is therefore not applicable for detecting diagnostic absorption features associated with this light condensate oil type, which is typical of the chemistry of many hydrocarbon oils found in the Australian Northwest Shelf area and condensates world wide. We conclude that oil type is critical to the applicability of optical remote sensing for natural oil slick detection and identification. We recommend that a sensor- and oil-specific sensitivity study should be conducted prior to applying optical remote sensors for oil exploration.The oil optical properties were obtained using two different laboratory methods, a reflectance-based approach and transmittance-based approach. The reflectance-based approach was relatively complex to implement, but was chosen in order to replicate as closely as possible real world remote sensing measurement conditions of an oil film on water. The transmittance-based approach, based upon standard laboratory spectrophotometric measurements was found to generate results in good agreement with the reflectance-based approach. Therefore, for future oil- and sensor-specific sensitivity studies, we recommend the relatively accessible transmittance-based approach, which is detailed in this paper.     

Fabrication of planar and three-dimensional microcoils on flexible substrates

Inductors are basic components of magnetic sensors. Generally, with those sensors, a weak magnetic variation has to be detected. As the sensitivity increases with the inductance value, our objectives are to design inductors with a maximum of turns while keeping millimetric sizes for the sensor. In this work, we present two microcoil fabrication processes compatible with rigid and flexible substrates. The first one is used for the realization of planar microcoils with one step of copper micromoulding. For example, a 40-turn microcoil of 1 mm external diameter and 5 μm copper width and spacing wires has been obtained. The second process allows the fabrication of three-dimensional microcoils (microsolenoids). It is based on two steps of copper micromoulding. In this process, a grey-tone photolithography step is implemented. Microsolenoids with 10–13 wires have been realized.     

基于磁通负反馈的低噪声宽频带感应式磁传感器设计

感应式磁传感器（IMS）是频率域电磁法（FEM）中使用最广泛的磁传感器,通常由感应线圈和前置放大器组成.为了增加IMS探测深度和微弱磁场信号的能力,基于磁通负反馈技术,获得其在低频段平坦的灵敏度曲线,拓宽了其观测频带.采用斩波前置放大技术,降低了1/f噪声对IMS的影响,对IMS的输出噪声进行了压制.通过在屏蔽室内对所研制的IMS性能进行测试,结果表明：其频带范围为0.001Hz ～10 kHz,输入噪声为3 nV/Hz1/2,较3D-3磁传感器等效输入噪声提高了10.04dB,为其在实际项目应用提供了可靠的性能保障.     

地震波、空间磁变及预警研究

介绍了一种基于巨磁磁阻GMR效应的高灵敏度三维加速度传感器和相关的磁传感器构成的惠斯通电桥电路组成的探测系统,通过对地震波波相及其空间磁变现象进行实时监测,根据地震发生前及发生过称程中空间磁场突变特征,予以提前预警,预警时间可提前到10～25min。从震动和磁变两方面对地震进行实时监测,大大提高了探测及预警的准确度。     

Fabrication of planar and three-dimensional microcoils on flexible substrates

Inductors are basic components of magnetic sensors. Generally, with those sensors, a weak magnetic variation has to be detected. As the sensitivity increases with the inductance value, our objectives are to design inductors with a maximum of turns while keeping millimetric sizes for the sensor. In this work, we present two microcoil fabrication processes compatible with rigid and flexible substrates. The first one is used for the realization of planar microcoils with one step of copper micromoulding. For example, a 40-turn microcoil of 1 mm external diameter and 5 μm copper width and spacing wires has been obtained. The second process allows the fabrication of three-dimensional microcoils (microsolenoids). It is based on two steps of copper micromoulding. In this process, a grey-tone photolithography step is implemented. Microsolenoids with 10–13 wires have been realized.

     

巨磁阻抗磁传感器研究进展

巨磁阻抗效应是指材料的交流阻抗在外加直流磁场的作用下发生显著变化的现象,利用该效应研制的巨磁阻抗磁传感器具有灵敏度高、体积小和功耗低等特点,具有巨大的应用前景.分析了巨磁阻抗磁传感器的研究现状,重点介绍了磁场传感器、电流传感器和生物传感器的工作原理和特性,并指出了其目前存在的问题和发展趋势.     

基于MSP430的磁弹性传感器检测系统设计

磁弹性传感器无线无源的优点使其在无损检测、在体分析等领域具有非常广阔的应用前景.通过对磁弹性传感器检测原理的分析,设计了一种基于MSP430平台的小型化磁弹性传感器检测系统.该系统以MSP430单片机为控制核心,利用永磁铁作为偏置磁场激励,集成了交流激励信号产生单元、有效值检测单元和AD采样单元,并通过RS-232实现与上位机之间的通信.实验结果表明:该检测系统可以方便快捷地实现对磁弹性传感器共振特性的检测,具有稳定性好、集成度高、功耗低的特点,能够满足磁弹性传感器在不同状态和环境下共振特性的精确检测需求.     

A hybrid capacitive pressure and temperature sensor fabricated by adhesive bonding technique for harsh environment of kraft pulp digesters

We have developed a compensated capacitive pressure and temperature sensor for kraft pulp digesters (pH 13.5, temperatures 25–175°C reaching a local maximum of 180°C and pressures up to 2 MPa). The gauge capacitive pressure sensor was fabricated by bonding silicon and Pyrex chips using a high temperature, low viscosity UV (ultraviolent) adhesive as the gap-controlling layer and heat curing adhesive as the bonding agent. A simple chip bonding technique, involving insertion of the adhesive into the gap between two chips was developed. A platinum thin-film wire was patterned on top of a silicon chip to form a resistance temperature detector (RTD) with a nominal resistance of 1,500 Ω. A silicon dioxide layer and a thin layer of Parylene were deposited to passivate the pressure sensor diaphragm and the sensors were embedded into epoxy for protection against the caustic environment in kraft digesters. The sensors were tested up to 2 MPa and 170°C in an environment chamber. The maximum thermal error of ±1% (absolute value of ±20 kPa) full scale output (FSO) and an average sensitivity of 0.554 fF/kPa were measured. Parylene-coated silicon chips were tested for a full kraft pulping cycle with no signs of corrosion.