Comparison of analysis methods for package-induced stresses on moulded Hall sensors

Due to the piezoresistive and the piezo-Hall effect in semiconductor materials, Hall sensors show a strong temperature dependency and also a drift when subjected to temperature cycles Manic et al. (2000). Four factors mainly influence the mechanical stress in the sensitive layer. These are the geometry of the device, the differences of the coefficients of thermal expansion of the package materials, the temperature-dependent material properties and the time-dependent, viscous material properties. The objective of this investigation was to determine the mechanical stress in a moulded Hall sensor during the packaging process by finite-element simulation in comparison to experimental methods. It is shown that after each process-step the mechanical stress in the sensitive layer changes over time depending on the absolute value and the rate of the temperature change. Measurements of the inverse bending radius of glued and moulded chips show good agreement to the simulations.

     

The influence of package-induced stresses on moulded Hall sensors

The output signals of moulded Hall sensors show changes in offset and sensitivity when the devices are affected by changing temperatures. This behaviour is a result of the differences in the thermal expansion behaviour of the package materials and is also affected by their time-dependent, viscous material properties. The stresses affected to the sensor’s sensitive layer will become effective via the piezo-Hall-effect as well as via piezo-resistivity which both change the sensitivity and the offset of the sensor’s output voltage. For modelling the stress in the sensitive area correctly it is indispensable to consider the visco-elastic and the visco-plastic behaviour of the materials constituting the package. Especially for very accurate sensors or components operating in harsh environments these effects must be regarded. In this work we investigate the thermo-mechanical stresses, which are induced in the sensitive layer of a moulded Hall sensor during the assembly process, the investigations were based mainly on finite-elements-simulations.     

An accurate compact model for CMOS cross-shaped Hall effect sensors

The paper describes a new design-oriented compact model for horizontal Hall effect devices. This model is based on the physics of semi-conductor and is simplified according to some assumptions verified through experimental results and/or numerical simulations. Compared to existing models, it has the advantage to take most of the first-order effects into account while allowing fast simulations. A procedure to extract the parameters of the model is given and simulation results are compared to experimental data measured on a cross-shaped sensor designed in a standard 0.35 μm CMOS technology. The maximum error between simulation results and experimental data is less than 1%.     

基于电流补偿的低精度霍尔传感器位置估计

为了降低永磁同步电动机伺服控制系统的成本,采用3个低精度开关型霍尔传感器作为转子位置检测装置来估算高精度的转子位置信息,并采取电流补偿的方法对启动及低速阶段的加速度进行估计,解决了传统的低精度控制技术在启动及低速阶段误差较大的问题。仿真结果表明,该方法能有效提高电动机在低速阶段的稳定性,减小转子位置估算误差,在全速范围内达到了良好的调速性能。     

电学量传感器通用线性处理方法

把电学量传感器测量物理量的范围，平分二段，分别建立拟合回归方程，并用电路实现之。这种线性处理方法具有通用性。以K型热电偶传感器为实验例子，未经线性处理前，理论线性度为3.2%，线性处理后，理论线性度为0.015%。测量数据标准差为0.00138。     

Investigations on excitation and detection methods for Lamb wave sensors

Due to a high potential sensitivity, Lamb wave acoustic sensors have been studied for biochemical applications. Usually, Lamb waves are generated and detected using piezoelectric transducers. This technology involves bilayers structures and causes some problem of induced strain and temperature compensation. In this paper, we have investigated optical and electrostatic excitation methods. The optical excitation of Lamb waves is studied, and the main limitations of such an excitation method are pointed out. Theoretical as well as experimental studies are reported on electrostatic excitation of Lamb waves, and it is shown that this technique can be suitable for biosensors.     

霍尔传感器在直流电机转速测量中的应用研究

采用霍尔传感器和AT89S52单片机控制步进直流电机转速,介绍了测速原理与软硬件设计方法。通过1602LCD显示电机转速值,根据需要可调整控制电机的转速。测试结果表明:该转速测量系统满足设计要求,具有硬件结构简单、性价比较高、易于调节电机转速及系统性能稳定等优点。     

0.2 mT Residual offset of CMOS integrated vertical Hall sensors

A residual offset lower than 0.2 mT is obtained with a CMOS integrated vertical Hall (VH)-sensor microsystem. Instead of the conventional design with five contacts in the sensor active area, we apply a layout with only four contacts. This design shows a higher effectiveness for the offset reduction by the spinning current (SC) method, because of the symmetrical current flow for the two different biasing phases. Furthermore, to obtain very low offsets, coupled sensors are integrated with the spinning current electronics in the final microsystem. A sensitivity up to S_v=0.025 V/VT is achieved for these sensors without any additional technology step. The measured output noise level of the integrated microsystem (1.9 μT/ ) is in the usual range of commercial integrated Hall-sensors. Our new developments open the way to the realization of compact, low-cost angular sensors with 10 bit resolution.     

提高振弦式传感器测量精度的方法研究

振弦式传感器是水利工程和结构监测中应用较为广泛的设备之一.针对振弦式传感器输出信号微弱、放大检测中容易受到干扰而造成的测量精度下降问题,通过一个大坝高边坡安全监测工程应用实例的研究,从硬件的合理设计和软件的数据处理两方面详细分析和有效解决了振弦式传感器测量过程中的干扰问题,大大提高了振弦式传感器的测量精度.     

Comparison among three analytical methods for knowledge communities group-decision analysis

Knowledge management can greatly facilitate an organization’s learning via strategic insight. Assessing the achievements of knowledge communities (KC) includes both a theoretical basis and practical aspect; however, a cautionary word is in order, because using improper measurements will increase complexity and reduce applicability. Group decision-making, the essence of knowledge communities, lets one considers multi-dimensional problems for the decision-maker, sets priorities for each decision factor, and assesses rankings for all alternatives. The purpose of this study is to establish the objective and measurable patterns to obtain anticipated achievements of KC through conducting a group-decision comparison. The three multiple-criteria decision-making methods we used, simple average weight (SAW), “Technique for Order Preference by Similarity to an Ideal Solution” (TOPSIS) and “VlseKriterijumska Optimizacija I Kompromisno Resenje” (VIKOR), are based on an aggregating function representing “closeness to the ideal point”. The TOPSIS and VIKOR methods were used to highlight our innovative idea, academic analysis, and practical appliance value. Simple average weight (SAW) is known to be a common method to get the preliminary outcome. Our study provides a comparison analysis of the above-three methods. An empirical case is illustrated to demonstrate the overall KC achievements, showing their similarities and differences to achieve group decisions. Our results showed that TOPSIS and simple average weight (SAW) had identical rankings overall, but TOPSIS had better distinguishing capability. TOPSIS and VIKOR had almost the same success setting priorities by weight. However, VIKOR produced different rankings than those from TOPSIS and SAW, and VIKOR also made it easy to choose appropriate strategies. Both the TOPSIS and VIKOR methods are suitable for assessing similar problems, provide excellent results close to reality, and grant superior analysis.     

Temperature coefficients of Hall sensors made of InSb/GaAs epitaxial layers

We discuss the impact of the temperature coefficients (TCs) of the Hall voltage χ, the resistance α, and the electron mobility λ on the output voltage TC of Hall sensors made of heavily donor doped epitaxial InSb/GaAs thin films. We point bout that in those n⁺-InSb epitaxial films, each of the TCs spans some range of magnitudes that include both negative and positive values. The concrete value of each of the TCs depends on the preparation technology and temperature range, however, the relationship γ = χ−α must hold. Thus, various combinations of the TCs can be realized, and some of them can minimize the output voltage TC in one of the feed regime: the constant driving current or the constant voltage regime. For example, λ is the TC that determines the output voltage TC in the driving voltage regime. We show that n⁺-InSb epitaxial films that have small λ in a broad temperature range can be obtained in special preparation conditions.     

Intelligent multichannel sensors for pulse wave analysis

Aortic pulse wave velocity is an independent predictive indicator for all cause mortality and cardiovascular morbidity. Unfortunately it is only invasively accessible and thus the A. carotis–A. femoralis pulse wave velocity (cfPWV) is recommended as a non-invasive substitute. This work presents a model based analysis method for the beat-to-beat online determination of an arbitrary, peripheral pulse transit time (PTT). The method is based on the recording of a three lead electrocardiography (ECG) and of pulse waves (PW) at a peripheral site such as the A. carotis by means of a multiple sensor array. The two modules for the signal acquisition work autonomously but time-wise simultaneously and transmit the data via a radio unit to the central processing unit. There the algorithms for the pulse transit time determination exploit these signals. In doing so the main focus is on an efficient implementation to assure real-time usability. The evaluation of the developed modules and algorithms was done in two separate trials. First the algorithms were tested offline against manual signal annotation using invasive data previously recorded to proof their accuracy. The resulting mean differences in PTT for pulse waves assessed at the aortic root and the aortic bifurcation are 2.86 ms (4.72 ms SD) and 2.00 ms (2.28 ms SD). To evaluate the whole system integrity in a second step online measurements on probands were carried out and compared to data from literature. The trials resulted in a mean PTT of 174.6 ms (17.7 ms SD) for the A. radialis and of 81.9 ms (13.2 ms SD) for the A. carotis. The results suggest that the method may be useful and deployable at general practitioners (GP) and in ambulatory care of (chronic) cardiovascular diseases.     

基于霍尔传感器的高准确度磁场测量方法

霍尔传感器的测量准确度容易受到安装工艺和环境温度变化的影响。介绍了几种提高霍尔传感器的磁场测量准确度的方法:零位误差补偿法,温度误差补偿法和电压比测量法。其中电压比测量法不需恒流源电路,可以有效地减小环境温度变化所引起的磁场测量误差。试验表明:采用电压比测量法进行磁场测量,其准确度可以达到0.5%以上。     

Comparison of methods for logic-query implementation

A logic query Q is a triple < G, LP, D, where G is the query goal, LP is a logic program without function symbols, and D is a set of facts, possibly stored as tuples of a relational database. The answers of Q are all facts that can be inferred from LP ∪ D and unify with G. A logic query is bound if some argument of the query goal is a constant; it is canonical strongly linear (a CSL query) if LP contains exactly one recursive rule and this rule is linear, i.e., only one recursive predicate occurs in its body. In this paper, the problem of finding the answers of a bound CSL query is studied with the aim of comparing for efficiency some well-known methods for implementing logic queries: the eager method, the counting method, and the magic-set method. It is shown that the above methods can be expressed as algorithms for finding particular paths in a directed graph associated to the query. Within this graphical formalism, a worst-case complexity analysis of the three methods is performed. It turns out that the counting method has the best upper bound for noncyclic queries. On the other hand, since the counting method is not safe if queries are cyclic, the method is extended to safely implement this kind of queries as well.     

无线局域网业务流预报方法比较

介绍了基于时间序列、神经网络和小波的多种网络业务的预报方法,应用真实的无线局域网业务流序列检验了这些模型的预报性能,结果表明,和其他预报模型相比,基于神经网络的模型能够比较精确地捕获无线局域网业务流自身的特性,对业务流具有良好的预报性能,而基于ARIMA模型的预报性能最差。     

Similarity-based analysis for large networks of ultra-low resolution sensors

By analyzing the similarities between bit streams coming from a network of motion detectors, we can recover the network geometry and discover structure in the human behavior being observed. This means that a low-cost network of sensors can provide powerful contextual information to building systems: improving the efficiency of elevators, lighting, heating, and cooling; enhancing safety and security; and opening up new opportunities for human-centered information systems. This paper will show how signal similarity can be used to calibrate a sensor network to accuracies below the resolution of the individual sensors. This is done by analyzing the similarity structures in the unconstrained movement of people in the observed space. We will also present our efficient behavior-learning algorithm that yields 90% correct behavior-detection in data from a sensor network comprised of motion detectors by employing similarity-based clustering to automatically decompose complex activities into detectable sub-classes.     

Comparison of boundary element and finite element methods for dynamic analysis of elastoplastic plates

Boundary and finite element methodologies for the determination of the response of inelastic plates are compared and critically discussed. Flexural dynamic plate bending problems are considered and a hardening elastoplastic constitutive model is used to describe material behaviour. The domain/boundary element methodology using linear boundary and quadratic interior elements and the finite element method with quadratic Mindlin plate elements are used in this work. The discretized equations of motion in both methodologies are solved by an efficient step-by-step time integration algorithm. Numerical results obtained are presented and compared in order to access the accuracy and computational efficiency of the two methods. In order to make the comparison as meaningful as possible, boundary and finite element computer codes developed by the author are used in this paper. In general, boundary elements appear to be a better choice than finite elements with respect to computational efficiency for the same level of accuracy.     

Propeller blade stresses,application of finite element methods

This paper presents results from application of shell elements for prediction of quasi static and dynamic stresses in marine propeller blades.Stresses and deformations calculated for ordinary geometry and highly scewed propellers are compared with experiments.Specially designed data generators are employed to facilitate the helicoidal geometry involved.     

Pressure nonlinearity of micromachined piezoresistive pressure sensors with thin diaphragms under high residual stresses

Thermal residual stress plays a significant role in the performance of microelectromechanical system (MEMS) pressure sensor devices. For example, the voltage span and pressure nonlinearity (PNL) on the voltage output of a pressure sensing element can be significantly affected by the residual stresses of passivation films on the silicon diaphragm. The objective of this study is to resolve a pressure nonlinearity problem in terms of silicon nitride residual stress and diaphragm thickness in order to meet the PNL design criteria within ±3% at 25 °C. The curvatures of wafers were measured and the film residual stresses were calculated. Finite element analyses (FEA) were conducted and correlated with the PNL experimental tests. To build a design window for optimization, a central composite design (CCD) method was utilized to significantly reduce the number of FEA runs. It is concluded that the residual stress of PECVD silicon nitride needs to be optimized and controlled in order to reduce the pressure nonlinearity.