Medium and interface components in impedance microbiology

Classic impedance microbiology (CIM) is based on the measurement of the impedance components that appear between a pair of electrodes submerged in a cell containing inoculated broth. Either a bipolar or a tetrapolar technique can be applied, requiring about 1 x 10(3) to 3 x 10(7) cells/ml to produce detectable changes in the impedance curves. Theoretical analysis of the electrode-electrolyte interface during bacterial growth is lacking, with no generally accepted measuring standards. Besides, there is considerable disagreement. We separated out the interface and medium components using the frequency variation technique (FVT) and also analyzed the interface reactance-resistance diagram, both before and after bacterial growth. Medium resistance Rm, interface reactance Xi, and interface resistance Ri, were quantified as time functions growth curves, from the complex bipolar impedance seen between two electrodes. We took into account the electrical current density, the temperature and the associated circuitry, also explaining the theoretical and experimental bases that justify the proposed dissecting procedure. It was found that, within the working frequency range, Rm, Ri, and Xi percental growth curves are frequency-independent, i.e., neither Rm(f), nor Xi(f) nor Ri(f) changed their slopes before, during and after bacterial growth. Besides, no alpha-dispersion effect in Rm curves was detected. It is concluded that impedance microbiology could become a fertile area for interdisciplinary knowledge; its development might offer new avenues for basic and applied research.     

Design and calibration of a large broadband dielectric measurementcell

A large dielectric measurement cell was designed and calibrated to operate over a 1-MHz to 3-GHz frequency range. The cell is much larger than commercially available cells and is useful for measuring samples with large-grain heterogeneities like concrete or rock. The cell works on a coaxial transmission line principle. Once the S parameters of the two end sections are calibrated, the S parameters of the sample region can be found. Then the complex permittivity of the sample can be deembedded. Because of the broad frequency range, three calibration methods are used for the low-, intermediate-, and high-frequency ranges. The accuracy of the cell is tested by measuring materials of a known dielectric constant. Error analysis is also performed to determine the uncertainty of the measurements     

A 141-dB Dynamic Range CMOS Gas-Sensor Interface Circuit Without Calibration With 16-Bit Digital Output Word

In this paper, we present the design and the characterization of a wide-dynamic-range interface circuit for resistive gas-sensors able to operate without calibration. The circuit is based on resistance-to-frequency conversion, which guarantees low complexity. The state-of-the-art of this measurement method has been improved first by separating the resistance value controlled oscillator circuit (RCO) from the sensing device, thus leading to higher linearity performance, and then by exploiting a novel digital frequency measurement system. Measurement results on a silicon prototype, designed in a 0.35-mum CMOS technology, show that the circuit achieves, without calibration, a precision in resistance measurement of 0.4% over a range of 4 decades and better than 0.8% over 5 decades (dynamic range, DR = 141 dB). Furthermore, after calibration, it reaches a precision of 0.4% for resistance values ranging between 1 kOmega and 1 GOmega, thus leading to a DR of 168 dB. The prototype chip consumes less than 15 mW from a 3.3-V supply.     

Study on impedance spectroscopy based on dynamic equivalent circuit of solar cell

This paper investigates the impedance spectroscopy of monocrystalline silicon solar cells (MSSC) and dye-sensitized solar cells (DSSC) using solar cell dynamic equivalent resistor-capacitance (RC) and capacitor sum capacitor (CSC) circuits. Firstly, these circuits effectively represent the dynamic behavior of MSSC and DSSC. Secondly, the measurement method significantly impacts the accuracy of impedance measurements in the high-frequency region. Finally, the series resistance affects the distance between the left end of the impedance spectroscopy and the origin, while the parallel resistance influences the size of the impedance spectroscopy. In the CSC circuit, the relative magnitudes of dielectric relaxation capacitance and chemical capacitance affect the number and position of arc in the impedance spectroscopy. The value of the dielectric relaxation capacitor determines the number of impedance spectroscopy arcs. These conclusions provide guidelines for improving the accuracy of solar cell impedance measurements.     

A method for measuring transients caused by interrupting currentusing a transmission line terminated in its characteristics impedance

A measurement method of transients caused by interrupting a current is described. In consideration of the fast transients and high-frequency discharge phenomena due to interrupting the current, a transmission-line system was introduced. It consists of a coaxial switch, coaxial cables as transmission lines on the right and left sides of the switch, and termination resistors. When the current is interrupted by the switch, the waveform across the termination resistor is measured by an oscilloscope. The impedance-matching technique for the cables was employed to minimize the effects of reflected waves. That is, the resistors were designed to match the characteristic impedance of the cables. The characteristics of the system were measured by a network analyzer. The VSWR of the system was within 1.33 in the frequency range below 500 MHz. The time-domain measurement using a transmission-line system terminated in its characteristic impedance clears up the process of the complicated transients caused by interrupting current     

An A.C magnetic field calibration system for SLF magnetic antenna Feng Shimin(冯士民), Zhou Suihua(周穗华), Chen Zhiyi(陈志毅),

Calibrating the super low frequency （SLF） magnetic antenna in magnetic free space or an outdoor environment is difficult and complicated due to the large size calibration instruments and lots of measurement times. Aiming to calibrate the SLF magnetic antenna simply and efficiently, a calibration system comprised of a multi-frequency source, an A.C constant-current source and a solenoid is proposed according to the characteristic of an SLF magnetic antenna. The static magnetic transfer coefficient of the designed solenoid is calibrated. The measurement of the frequency response characteristics suggests the transfer coefficient remains unchanged in the range of the SLF band and is unaffected by the magnetic antenna internally installed. The CORDIC algorithm implemented in an FPGA is realized to generate a linear evenly-spaced multi-frequency signal with equal energy at each frequency. An A.C constant weak current source circuit is designed in order to avoid the impact on the magnetic induction intensity of a calibration system affected by impedance variation when frequency changing, linearity and the precision of the source are measured. The frequency characteristic of a magnetic antenna calibrated by the proposed calibration system agrees with the theoretical result and the standard Glass ring calibration result. The calibration precision satisfies the experimental requirement.     

A High-Power Automatic Network Analyzer for Measuring the RF Power Absorbed by Biological Samples in a TEM Cell

A device for measuring the radiofrequency (RF) power absorbed by biological samples while they are being irradiated in a transverse electromagnetic (TEM) cell is described. The report discusses the design, calibration, and performance of this automated measurement system. The power absorption analyzer is based on a six-port type of automatic network analyzer, and operates at an incident power to the TEM cell of 1 to 1000 W, over a frequency range of 100 to 1000 MHz. Experiments show that an absorbed power of 0.02 to 0.05 percent of the incident power can he measured. Measurements of the power absorbed by a 1-percent saline solution were made rising the power absorption analyzer and by an independent calorimetric measurement. The two measurement techniques show excellent agreement.     

基于嵌入式技术的靶场破片测速系统设计

为了增强靶场破片测速系统的便携性和实时性,提出了一种基于嵌入式技术的靶场破片测速系统设计方法。系统硬件上采用ARM＋FPGA的架构,软件上不仅采用Qt／Embedded设计了图形界面,而且给出了嵌入式设备上Qt／Embedded程序的优化方法。经过多次野外破片测速试验检测,系统工作稳定,可实现破片飞行速度、速度降、末速度、破片速度分布等参数的获取。试验结果证明,系统能够满足靶场破片测速的大多数需要。     

Enhanced through-reflect-line characterization of two-portmeasuring systems using free-space capacitance calculation

A through-reflect-line (TRL) calibration procedure is presented wherein the free-space capacitance and propagation factor of the line standard are used to determine the complex, frequency-dependent characteristic line impedance. The impedance is used in the conventional TRL, so the method is designated the ETRL (enhanced TRL) method. The method is applied to measurement of a microstrip via. The results show that the PCB via model used needs to be modified at frequencies above 2 GHz     

仿真耳耦合腔声转移阻抗自动测量系统的设计

基于新的IEC60318-1国际标准,设计并实现了一套仿真耳耦合腔声转移阻抗的自动测量系统.该系统能够完成100 Hz～10 kHz频率范围内1/N倍频程频率点上声转移阻抗的自动测量,并具有测量速度快、效率高、易于操作等特点.试验结果表明,该系统能够满足国际标准的相关要求,可为仿真耳的生产产商或使用单位提供测量校准服务.     

采用张量分解的四摄像机测量系统标定方法

摄像机标定是精密三维视觉测量的关键,为了实现对多摄像机测量系统的精确标定,首先分析了现有基于一维靶标的多摄像机标定方法的优缺点,并针对其不足,提出了一种基于张量分解的多相机标定方法,该方法主要包括以下三个方面的内容:(1) 利用透视投影成像模型和刚体变换理论建立多摄像机测量的数学模型;(2) 分析现有基于基本矩阵的多摄像机标定方法存在标定结果之间相互耦合的问题;(3) 将四摄像机测量系统的四焦张量引入标定过程中,利用一维标定靶标的成像点坐标求解的四摄像机测量系统的四焦张量,并根据四焦张量的简化求解方法来精炼获取摄像机矩阵。最后,通过实验验证了该方法的有效性和准确性,实验结果表明:(1) 四摄像机三维测量系统的标定可仅通过三组标定靶标图像即可实现,且标定操作效率相对于基本矩阵法更高;(2) 在4000 mm×4000 mm×2000 mm范围内,多摄像机测量系统的精度达到4 mm (3σ),相比于传统方法具有更精确的标定结果。满足室内运动目标位姿精确测量的要求。     

基于阵列天线测量装备的标校方法研究

介绍了一般测量装备的标校方法及步骤,对基于阵列天线测量装备的标校方法做了进一步论述。利用此标校方法,解决了基于阵列天线的测量装备测量数据处理的精确度问题,通过测量值与提供的真值比较,结果表明该标校方法合理实用并且精度较高,提高了装备保障水平,该研究成果可为靶场其他测量装备的标校提供借鉴。     

A technique for power supply harmonic impedance estimation using acontrolled voltage disturbance

A method for power system impedance estimation is presented. The method employs a power converter to inject a voltage transient onto the supply system. As the technique employs controlled power electronic devices it may be used as a stand alone piece of a portable measurement equipment, or it may be embedded into the functions of an active shunt filter for improved harmonic control. The impedance is estimated through correlation of the measured voltage and current transients. Simulations and experimental results demonstrate the measurement technique is highly accurate and effective     

压电结构测控系统中的电压衰减接口设计

针对压电智能结构在减振降噪领域的应用,基于NI 6343数据采集卡设计了一种无源10×衰减接口,扩大了输入电压范围,解决了基于NI 6343数采卡搭建压电测控实验系统的设计方案。该文首先分析建立了压电元件输出阻抗模型,在此基础上讨论了测试系统负载效应对压电元件输出电压的影响,最后设计了10×接口电路,并分析讨论了其幅频、相频特性。仿真和实验结果表明,所设计的10×接口可以用于直接测量采集的大多数压电元件的输出电压信号,且在1 000 Hz以内均有较高的幅值测量精度。     

Design and calibration of a high-frequency oscillatory ventilator

High-frequency ventilation (HFV) is a modality of mechanical ventilation which presents difficult technical demands to the clinical or laboratory investigator. The essential features of an ideal HFV system are described, including wide frequency range, control of tidal volume and mean airway pressure, minimal dead space, and high effective internal impedance. The design and performance of a high-frequency oscillatory ventilation system is described which approaches these requirements. The ventilator utilizes a linear motor regulated by a closed loop controller and driving a novel frictionless double-diaphragm piston pump. Finally, the ventilator performance is tested using the impedance model of Venegas [1].     

Six-port self-calibration based on active loads synthesis

An automatic method for self-calibrating six-port reflectometers is reported in this paper. It is based on the use of an active impedance synthesis system. This self-calibration method allows a completely autonomous operation, reduces measurement errors caused by the frequent connecting and disconnecting of calibration standards, and is suitable for low and high frequencies, where sliding shorts are difficult to manufacture. In addition, it simplifies operation of six-port reflectometers to nonspecialized users. The experimented impedance synthesis presented relies on an in-phase and quadrature vector modulator, and the entire system is computer controlled     

数字信号处理在雷达相噪测量中的应用

随着通信和雷达的发展,脉冲信号的相位噪声成了影响整个系统性能的重要因素之一,采用传统模拟相位检波法测量脉冲信号相位噪声是一个非常大的挑战,因为这样的测试系统非常复杂,并且在测量相位噪声之前需要非常繁琐的校准程序,先进的正交数字相位解调和幅度解调技术能很好地解决这个问题。采用正交数字相位解调和幅度解调技术的系统不需要相位检波器和复杂的校准程序,利用极低噪声的参考源和互相关技术,提高了系统动态范围和测量灵敏度,实现了一键式精密测量脉冲相位噪声和调幅噪声。     

Practical Implementation of a High-Frequency Current-Sense Technique for VRM

To track the inductor current in high-frequency dc/dc converters is not effortless, particularly when high output currents and low output voltages are demanded by the load. This paper proposes a simple technique to obtain a good accuracy in the inductor current measurement in voltage regulator module (VRM) applications. The main idea is to obtain an equivalent voltage image which can be used for the high-frequency pulsewidth modulation controller to generate the converter control law. This strategy of measurement is generic, and it has been previously validated by simulations. Afterward, some experimental results are obtained by using several prototypes of dc/dc converters delivering a very low output voltage and owning several loads from 10-mA to 100-A currents. This wide range covers the power requirements of portable and embedded VRM applications. Moreover, this sense technique has also been validated in a digital high-frequency current-mode-controlled dc/dc converter.      

基于TWAIN接口的图像测量系统的设计

介绍了TWAIN接口的标准,并分析了开发基于TWAIN接口的应用程序的方法.建立了基于TWAIN接口的图像测量系统,并分析了其测量的原理及标定的方法.位移测量的实验结果证明图像测量系统可应用于位移、长度、直径等工件尺寸的测量.     

On-wafer photoconductive sampling of MMICs

A practical technique for the on-wafer characterization of the high-frequency response of a MMIC was developed, using photoconductive (PC) sampling. It provides S-parameter measurement with broadband, high sensitivity, and accurate calibration. In addition, due to its inherent broadband signal generation on the wafer, high-frequency information of the circuits can be extracted merely by using DC probes. Starting from a hybrid testing configuration, the compatibility of PC switch fabrication with the MMIC production process is demonstrated. In this phase, 40-dB dynamic range in the S-parameter measurement was achieved. The success motivated the monolithic integration of the PC switches onto the MMIC. Efforts were made to reduce the size of the optical test structure. Good agreement between a conventional network analyzer measurement and two optical testing results has been achieved, showing that built-in optical test structures can be designed to have comparable overall size with existing CPW test structures. The S-parameter characterization of a nonlinear transmission line is demonstrated