阶跃阻抗谐振器结构的双频差分天线

提出了一种采用阶跃阻抗谐振器(SIR)结构设计的同轴馈电双频差分天线.天线具有对称结构,其传输线模型包含两个谐振单元.通过对谐振单元的简化和分析,证明了谐振单元类似于标准的1/4波长SIR,并导出了谐振单元的电长度和阻抗比与双频天线工作频率的关系.依照该方法设计了一个2.4/5.2 GHz的双频差分天线,同时用模型仿真...     

衰减法测Q值原理分析

Q值是为描述谐振回路中损耗电阻的影响而引进的阻抗参量。一般将回路Q值又细分为回路真实Q值和回路有效Q值两种,并确定前者用通频带法测定,后者用串联谐振原理测定。那么用衰减法测量原理(如HL 2801     

高性能生物电测量电路设计与参数自动测试

设计了一种具有皮肤接触阻抗同步检测功能的生物电测量电路,采用同相并联方式输入,结合仪表放大器以及共模驱动电路以获取高共模抑制比.利用微电流交流恒流源,在测量生物电信号的同时可检测皮肤接触阻抗.电路还具有50 Hz陷波、低通、高通滤波等功能.为了测试电路性能指标,设计了基于Labview的放大器性能自动测试平台,可对放大器幅频特性、共模抑制比进行实时动态测试.实际测量结果表明:生物电信号放大器性能优异,可获得120 dB的共模抑制比,能够用于心电、脑电、肌电等生理电信号测量.     

石英晶体元件负载谐振频率测量技术的研究

在分析与对比三种测量石英晶体元件负载谐振频率方法的基础上,设计适用于测量法的π网络与整个测量系统,采用自动网络分析仪测量晶体的阻抗,采用测量法测出负载谐振频率.实验表明,在1 MHz～200MHz频率范围内,系统对负载谐振频率重复测量一致性能达到士1×10-6以内,在30 MHz～200MHz频段,测量误差达到士2×10-6以内.     

基于压电动态信息的便携式阻抗测量系统设计

为解决对大型基础设施微小损伤检测所使用的阻抗分析仪昂贵且不便于携带的问题,采用基于压电阻抗的结构健康诊断技术,检测附着于结构表面的压电材料的阻抗,设计开发出一种便携式的小型阻抗测量系统.通过对机械结构中螺栓松动的情况反复实验,证明此便携式阻抗测量系统的精确度与目前商用的多用途阻抗分析仪相差无几,不但可以对机械结构进行实时在线损伤检测,而且对于微小损伤的检测也非常有效.     

超磁致伸缩振动器谐振频率自感知机理研究

振动系统工作在谐振频率处则其工作效率最高,但由于受到负载、温度等因素的影响,其谐振频率往往会发生漂移,为了实现对振动系统工作频率的自动调节,提高系统的工作效率,提出采用搜索振动系统速度阻抗的方法,在无需安装检测谐振频率传感器的条件下,实现振动系统谐振工作点的自感知,并能快速、方便地自动跟踪系统的谐振频率。设计了超磁致伸缩振动器,并给出了振动器机械阻抗的表达式;在分析超磁致伸缩材料磁-机耦合关系的基础上,建立了超磁致伸缩振动系统的速度、阻抗及所受外力的自感知模型;在研制的实验系统上,验证了振动系统谐振频率自感知方法的可行性与正确性。     

火工品高频段射频阻抗测试技术?

为测量高频段火工品射频阻抗,根据火工品脚线和矢量网络分析仪的结构特点,设计了火工品专用连接夹具,实现了同轴和平行线的有效连接。并对夹具引入的测量误差进行了修正计算,建立了基于矢量网络分析仪的高频段火工品射频阻抗测试系统。利用此系统,测量了火工品1~18 GHz范围内的射频阻抗,共出现了5个谐振点,在谐振点火工品从电磁环境中吸收的能量最大,为评价火工品在电磁环境中的安全性提供了数据支撑。     

浅谈浊度计的检定

浊度计是用于测量悬浮于水（或其他透明液体）中,不溶性颗粒物质所产生的光的散射或衰减的程度,并定量表征这些悬浮颗粒物质含量的仪器。常用光电浊度计主要由光源、光的准直系统、样品测量池、测量室、光电检测元件和显示系统等部分组成。按测量原理或方式可分为光透射衰减、光散射、散射透射以及积分球等几种方式。     

浅谈浊度计的检定

浊度计是用于测量悬浮于水（或其他透明液体）中不溶性颗粒物质所产生的光的散射或衰减的程度，并定量表征这些悬浮颗粒物质含量的仪器。常用光电浊度计主要由光源、光的准直系统、样品测量池、测量室、光电检测元件和显示系统等部分组成。按测量原理或方式可分为光透射衰减、光散射、散射透射以及积分球等几种方式。     

多层粘接材料深层界面脱粘的超声谐振检测方法

针对多层粘接材料深层界面脱粘检测问题,使用超声谐振检测法进行研究.基于弹簧质量模型分析超声谐振检测的基本原理.在有限元软件中建立某构件二界面脱粘的声谐振检测模型,得到不同大小缺陷以及无缺陷条件下的检测信号,计算得出模型的谐振频率曲线,分析比较典型谐振频率下信号的衰减程度.使用超声谐振检测仪对置有不同大小尺寸人工缺陷试件...     

Theoretical, numerical, and experimental investigation on resonant vibrations of piezoceramic annular disks

In this study, vibration characteristics of thin piezoceramic annular disks with stress-free boundary conditions are investigated by theoretical analysis, numerical simulation, and experimental measurement. The nonaxisymmetric, out-of-plane (transverse), and axisymmetric in-plane (tangential and radial extensional) vibration modes are discussed in detail in terms of resonant frequencies, mode shapes, and electrical currents. Two optical techniques, amplitude-fluctuation electronic speckle pattern interferometry (AF-ESPI) and laser Doppler vibrometer (LDV), as well as the electrical impedance measurement are used to validate the analytical results. Both theoretical and experimental results indicate that the transverse and tangential vibration modes cannot be determined by the impedance analysis; hence, only resonant frequencies of extensional vibration modes are presented from the impedance analyzer. The LDV system is used to measure the resonant frequencies of transverse vibrations. However, both the transverse and extensional vibration modes and resonant frequencies of piezoceramic annular disks are obtained by the AF-ESPI method, and the interferometric fringes are produced instantly by a video recording system. Numerical results obtained by finite-element calculations are compared with those from theoretical analysis and experimental measurements. It is shown that the theoretical predictions of resonant frequencies and the corresponding mode shapes agree well with the experimental results. Good agreement between the predicted and measured electrical impedance also is found. The dependence of resonant frequencies and dynamic electromechanical coupling coefficients on the inner-to-outer radius ratio also is analyzed and discussed in this study.     

Vibration characteristics of composite piezoceramic plates at resonant frequencies: experiments and numerical calculations

The experimental measurement of the resonant frequencies for the piezoceramic material is generally performed by impedance analysis. In this paper, we employ an optical interferometry method called the amplitude-fluctuation electronic speckle pattern interferometry (AF-ESPI) to investigate the vibration characteristics of piezoceramic/aluminum laminated plates. The AF-ESPI is a powerful tool for the full-field, noncontact, and real-time measurement method of surface displacement for vibrating bodies. As compared with the conventional film recording and optical reconstruction procedures used for holographic interferometry, the interferometric fringes of AF-ESPI are produced instantly by a video recording system. Because the clear fringe patterns measured by the AF-ESPI method will be shown only at resonant frequencies, both the resonant frequencies and corresponding vibration mode shapes are obtained experimentally at the same time. Excellent quality of the interferometric fringe patterns for both the in-plane and out-of-plane vibration mode shapes are demonstrated. Two different configurations of piezoceramic/aluminum laminated plates, which exhibit different vibration characteristics because of the polarization direction, are investigated in detail. From experimental results, we find that some of the out-of-plane vibration modes (Type A) with lower resonant frequencies cannot be measured by the impedance analysis; however, all of the vibration modes of piezoceramic/aluminum laminated plates can be obtained by the AF-ESPI method. Finally, the numerical finite element calculations are also performed, and the results are compared with the experimental measurements. Excellent agreements of the resonant frequencies and mode shapes are obtained for both results.     

Low Force Measurement Based on Impedance of a Piezo-resonator

Piezoelectric transducers have effectively been used for force measurement due to their inherently large stiffness. The primary transduction parameter of piezoelectric transducer is voltage which is used mostly for dynamic and sometimes for quasi-static force measurement. Other parameters of piezoelectric transducers such as resonant frequency, electrical impedance, etc. have also been used for force measurement. In the present work, precision measurement of conductance of a radial mode piezo-resonator has been carried out under different static loading and the resultant change in resonant conductance of the resonator have been evaluated as a function of loading force. This method based on resonant conductance measurement can prove to be effective in measuring forces between two interfaces which is an important requirement in many scientific and technical problems.     

一种新型的交流阻抗计量标准装置

为解决任意阻抗模与阻抗角的交流阻抗的溯源问题,研制了一套新型交流阻抗标准装置,由交流阻抗标准源及交流阻抗标准表组成,在100Hz~1MHz、0.1Ω~1kΩ范围,可对RLC数字电桥、交流阻抗和实物阻抗进行校准,技术指标可以达到0.01%。采用直接测量法、替代测量法和等电位测量法,将交流阻抗标准溯源到实物阻抗标准、电压比例标准和相位标准上,形成了一条完整的交流阻抗溯源链。     

Theoretical analysis and experimental measurement for resonant vibration of piezoceramic circular plates

Based on the electroelastic theory for piezoelectric plates, the vibration characteristics of piezoceramic disks with free-boundary conditions are investigated in this work by theoretical analysis, numerical simulation, and experimental measurement. The resonance of thin piezoceramic disks is classified into three types of vibration modes: transverse, tangential, and radial extensional modes. All of these modes are investigated in detail. Two optical techniques, amplitude-fluctuation electronic speckle pattern interferometry (AF-ESPI) and laser Doppler vibrometer (LDV), are used to validate the theoretical analysis. Because the clear fringe patterns are shown only at resonant frequencies, both the resonant frequencies and the corresponding mode shapes are obtained experimentally at the same time by the proposed AF-ESPI method. Good quality of the interferometric fringe patterns for both the transverse and extensional vibration mode shapes are demonstrated. The resonant frequencies of the piezoceramic disk also are measured by the conventional impedance analysis. Both theoretical and experimental results indicate that the transverse and tangential vibration modes cannot be measured by the impedance analysis, and only the resonant frequencies of extensional vibration modes can be obtained. Numerical calculations based on the finite element method also are performed, and the results are compared with the theoretical analysis and experimental measurements. It is shown that the finite element method (FEM) calculations and the experimental results agree fairly well for the resonant frequencies and mode shapes. The resonant frequencies and mode shapes predicted by theoretical analysis and calculated by finite element method are in good agreement, and the difference of resonant frequencies for both results with the thickness-to-diameter (h/D) ratios, ranging from 0.01 to 0.1, are presented.     

Ultrasonic Transducer Sensitivity and Model-Based Transducer Characterization

It is shown that the role that an ultrasonic piezoelectric transducer plays in both generating and receiving ultrasound in an ultrasonic nondestructive evaluation (NDE) measurement system can be completely described in terms of the transducer's electrical impedance and open-circuit, blocked force receiving sensitivity. Furthermore, it is shown that both of these quantities can be obtained experimentally via a model-based approach and purely electrical measurements. The measurement of sensitivity uses a method originally developed for lower-frequency acoustic transducers. However, it is shown that at the higher frequencies found in ultrasonic NDE applications electrical cabling effects play an important role and must be compensated for in determining the transducer sensitivity. Examples of experimental measurement results using these new approaches are given.     

Ultrasonic Transducer Sensitivity and Model-Based Transducer Characterization

It is shown that the role that an ultrasonic piezoelectric transducer plays in both generating and receiving ultrasound in an ultrasonic nondestructive evaluation (NDE) measurement system can be completely described in terms of the transducer's electrical impedance and open-circuit, blocked force receiving sensitivity. Furthermore, it is shown that both of these quantities can be obtained experimentally via a model-based approach and purely electrical measurements. The measurement of sensitivity uses a method originally developed for lower-frequency acoustic transducers. However, it is shown that at the higher frequencies found in ultrasonic NDE applications electrical cabling effects play an important role and must be compensated for in determining the transducer sensitivity. Examples of experimental measurement results using these new approaches are given.     

A 0-phase circuit for QCM-based measurements in highly viscous liquid environments

Currently, the series resonant frequency f/sub s/ and the motional resistance Rm of liquid loaded quartz crystal microbalance (QCM) sensors are extracted either directly, through network analyzer (NWA) impedance measurements, or from QCM-stabilized oscillator circuits. Both methods have serious drawbacks that may affect measurement accuracy, especially if the sensor is operated under highly viscous load conditions and Rm exceeds 1 k/spl Omega/. This paper presents a simple passive low-loss impedance transformation LC network which greatly reduces additional electrical loading of the QCM by the measurement system or sensor electronics and maintains a symmetric resonance and a steep 0-phase crossing at f/sub s/, even if Rm increases by several orders of magnitude as a result of liquid loading. A simple S21 transmission measurement allows direct f/sub s/ reading at the 0-phase frequency, while Rm is obtained from the circuit loss at f/sub s/. Circuit operation was verified at 9 MHz by QCM measurements in a liquid with known density and viscosity. The agreement between predicted and experimental data, which was obtained by a temperature-controlled measurement, was within 1%, even in very high viscosity ranges in which Rm exceeds 10 k/spl Omega/.     

交流功率标准构建原理及发展趋势综述

交流功率标准作为电能计量最重要的溯源源头,对确保电能贸易结算的公平公正具有基础支撑作用。对目前构建高精度交流功率标准的常用方法以及功率量值溯源的链路进行了阐述。通过分析基于交流功率标准的电能表校准过程的误差来源,确立了主要的测量不确定度分量。针对现有交流功率标准存在的局限性,以及新型电力系统对电能计量提出的新需求,展望了电能计量标准未来的发展趋势。     

Ultrasonic Transducer Sensitivity and Model-Based Transducer Characterization

Abstract

It is shown that the role that an ultrasonic piezoelectric transducer plays in both generating and receiving ultrasound in an ultrasonic nondestructive evaluation (NDE) measurement system can be completely described in terms of the transducer's electrical impedance and open-circuit, blocked force receiving sensitivity. Furthermore, it is shown that both of these quantities can be obtained experimentally via a model-based approach and purely electrical measurements. The measurement of sensitivity uses a method originally developed for lower-frequency acoustic transducers. However, it is shown that at the higher frequencies found in ultrasonic NDE applications electrical cabling effects play an important role and must be compensated for in determining the transducer sensitivity. Examples of experimental measurement results using these new approaches are given.