共查询到19条相似文献,搜索用时 215 毫秒
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提出了一种采用压电矩形鼓和永磁铁的小型电流传感器。基于安培定律,永磁铁感受电流变化并驱动压电矩形鼓振动,压电矩形鼓因压电效应将振动转化为电信号输出,从而实现电流传感。利用有限元分析方法研究了电流传感器的一阶振动模态及其应力分布,并计算了电流传感器的灵敏度频率响应特性,其与实验结果较吻合。实验结果表明,该电流传感器在一阶谐振频率204 Hz处具有较高的灵敏度(0.95 V/A),在动态范围0.005 A~30 A内具有良好的线性度(0.3%);与采用压电悬臂梁结构的电流传感器相比,具有更好的稳定性。文中提出的传感器结构还可以应用于振动信号、磁场的长期不间断测量或监测。 相似文献
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针对当前非接触电流测量方式存在的灵敏度低、结构复杂等问题,本文提出了一种采用压电复合音叉的电流传感器用于非接触低频微弱电流测量,其结构由永磁体、弹性音叉、压电片及底座组成.当该传感器处于电线周围交变磁场中时,永磁体在磁场作用下产生扭矩并驱动弹性音叉臂及压电片产生形变;因压电效应,形变的压电片两端电极之间输出交变电压信号,从而实现电流的测量.由于磁扭矩效应,这种传感器具有较高的谐振灵敏度,大约是压电悬臂梁式电流传感器的4.0倍;在负载电阻为10 MΩ、频率为41.7 Hz时,灵敏度可达1.393 V/A,线性度约为0.57%.这种压电复合音叉式电流传感器模型还可以应用于微弱振动、磁场信号探测等. 相似文献
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木文把压电石英传感器的固有特点与岩土介质压力测量的特殊要求有机地联系起来,论述了压电石英及传感器在岩土压力测量中,具有匹配件性能稳定、宽量程范围内线性好、频响特性好、稳定性好等待。同时,介绍了几种传感器的综合性能和现场应用简况,从而展示了压电石英压力传感器在岩土工程中的应用前景。 相似文献
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医用超导磁共振主磁体在励磁过程中出现的交流损耗和传导漏热等情况,是超导磁体失超的根本原因;为了控制和保证励磁过程的稳定性、可靠性和安全性,开发和完善励磁的测控系统就显得格外重要;设计并开发了基于LabVIEW平台的超导磁共振主磁体励磁测控系统;系统数据通过在虚拟仪器平台上调用动态链接库文件(DLL),控制泰克公司KE2700系列集成式采集卡采集得到;传感器选择根据相应功能需要配置;操作台仪器控制、数据采集程序和人机界面由LabVIEW编写;搭配保护电路,保护超导线圈,降低失超损失;实现数据采集、参数控制、失超保护、匀场测试等功能。系统满足设计开发目的,平台搭建稳定可靠;功能相对完善,具体操作简易,交互界面友好,后期修改和功能扩展灵活;经工程实际运行测试验证,提高了研究和工作效率,达到设计要求,有实际应用价值。 相似文献
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This paper describes a method to control and detect droplet size gradient by step-wise flow rate ramping of water-in-oil droplets
in a microfluidic device. The droplets are generated in a cross channel device with two oil inlets and a water inlet. The
droplet images are captured and analyzed in a time sequence in order to quantify the droplet generation frequency. It is demonstrated
that by controlling the ramping of the oil flow rates it is possible to manipulate the ramping of droplet sizes. Increasing
or decreasing of droplet sizes is achieved for a step-wise triangular ramping profile of the oil flow rate. The dynamic behavior
of droplets due to the step-wise flow pulses is investigated. Uniform linear size ramping of water-in-oil droplets from 73
to 83 μm in diameter is generated with an oil flow ramping range from 1 to 11 μL/min in a minimum of five steps while water
flow rate is held constant at 2 μL/min. 相似文献
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石英晶体压电式力传感器的
单晶【djm】转换及晶组的排列与组合 总被引:1,自引:0,他引:1
本文深入研究了石英晶体的[d_(jm)]较换,晶组的排列与组合,从压电原理与工艺理论方面给出了单元与复合晶组的构成形式。对一些新形式的传感器在理论与实践方面给以明确的阐述。 本文不仅对压电式传感器研制与使用有重要的意义,而且对新型传感器的开拓具有重要的参考价值。 相似文献
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Ming Chun Hsieh Yean Kuen Fang Ming-Shaung Ju Gin-Shin Chen Jyh-Jier Ho Yang C.H. Pei Ming Wu Wu G.S. Terry Yuan-Fang Chen 《Journal of microelectromechanical systems》2001,10(1):121-127
A prototype contact-type micro piezoresistive shear-stress sensor that can be utilized to measure the shear stress between skin of stump and socket of above-knee (AK) prosthesis was designed, fabricated and tested. Micro-electro-mechanical system (MEMS) technology has been chosen for the design because of the low cost, small size and adaptability to this application. In this paper, the finite element method (FEM) package ANSYS has been employed for the stress analysis of the micro shear-stress sensors. The sensors contain two transducers that will transform the stresses into an output voltage. In the developed sensor, a 3000×3000×300 μm3 square membrane is formed by bulk micromachining of an n-type (100) monolithic silicon. The piezoresistive strain gauges were implanted with boron ions with a dose of 1015 atoms/cm2. Static characteristics of the shear sensor were determined through a series of calibration tests. The fabricated sensor exhibits a sensitivity of 0.13 mV/mA-MPa for a 1.4 N full scales shear force range and the overall mean hysteresis error is than 3.5%. In addition, the results simulated by FEM are validated by comparison with experimental investigations 相似文献
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Sebastian Maneth 《Information and Computation》1998,147(2):111
Attributed tree transducers are abstract models used to study properties of attribute grammars. One abstraction which occurs when modeling attribute grammars by attributed tree transducers is that arbitrary trees over a ranked alphabet are taken as input, instead of derivation trees of a context-free grammar. In this paper we show that with respect to the generating power this isnotan abstraction; i.e., we show that attributed tree transducers and attribute grammars generate the same class of term (or tree) languages. To prove this, a number of results concerning the generating power of top-down tree transducers are established, which are interesting in their own. We also show that the classes of output languages of attributed tree transducers form a hierarchy with respect to the number of attributes. The latter result is achieved by proving a hierarchy of classes of tree languages generated by context-free hypergraph grammars with respect to their rank. 相似文献
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Abstract— The exoemission of electrons from the MgO cathode surface has a great impact on many properties of plasma displays and needs to be carefully engineered for successful display products. A method for direct measurement of this exoemission current using an ultra‐high‐impedance amplifier, which detects the integrated exoemission charge collected by a capacitance, is presented. The large discharge and displacement currents initiated by the changing sustain waveform, which could overload and saturate the sensitive amplifier, are shorted by a very low impedance switch in the form of a common reed relay. The exoemission current from the MgO cathode is significantly amplified by avalanches in the gas, and thus methods for directly measuring the avalanche amplification factor so as to correct the measured current and obtain the true exoemission current from the cathode are described. This highly variable avalanche amplification factor is measured and estimated to be as large as 500 when the voltage across the gas is just below breakdown. Methods are covered to correct for the small ion currents that flow in the plasma‐panel soda glass substrates and that add an unwanted error signal. Practical circuit techniques for measuring the very small exoemission currents are presented. 相似文献
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高压熔断器是一种用在高压线路和配电系统中的保护装置,可对故障电路予以安全保护。其结构中石英砂填料的密实度对熔断器的安全性能至关重要,为此本文探究了一种径向冲击旋转熔管的方式来解决熔断器中填料的密实度问题。石英砂颗粒在冲击作用下进行位置的重新排列来降低孔隙率,进而提高填充密实度。本文采用离散元素法,建立了颗粒接触过程的动力学方程,应用EDEM软件模拟了石英砂的振动过程,并通过石英砂填料的填充实验进行了验证。结果证明:径向冲击旋转熔管方式可以使熔管填料的平均密实度达到1.65 g/cm3的密实度要求,同时随着振动时间的增加填充密实度表现出先增加后稳定的规律。 相似文献
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针对多声道超声波流量计在流体流速测量时由于单个或多个换能器不能正常工作而导致测量存在误差的问题。提出在多传感器数据融合理论的基础上对其进行改进,使其适用于多声道超声波流量计的数据融合计算,同时改进后的最优加权数据融合方法能够在每次测量后自适应的计算最优权重系数。通过实验表明当流量计各声道均能正常工作时,该方法与Gauss-Jacobi积分法计算得到的流速值基本一致,当流量计单个声道不能正常工作时,应用该方法可以得到比Gauss-Jacobi积分法更加稳定的流速值,能够减小测量误差对计算结果的影响。 相似文献
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石英挠性加速度计的内部力矩器噪声对于高精度的加速度计应用系统的影响是不可忽视的,但很少引起高度重视.针对高精度加速度计电路应用需要,研究了力矩器机械热噪声和力矩器线圈谐振的影响,建立了表头内部力矩器噪声电路模型,设计了测试电路,并对噪声电路模型进行了测试与验证.理论和实验结果均表明:机械热噪声产生的等效加速度对系统影响较小,力矩器线圈影响的谐振与驱动方式及驱动频率有关,脉宽调制(PWM)波驱动方式较正弦波驱动方式产生的谐振影响更大,当驱动频率靠近谐振点时,产生毫安(mA)级的谐振电流.模型的建立对石英挠性加速度计应用具有较好的参考价值. 相似文献