电涡流传感器的脉冲激励与双参数检测

采用矩形脉冲作为激励信号,对电涡流传感器在位移检测过程中谐振频率及谐振阻尼的变化情况进行了研究分析.建立了以现场可编程门阵列(FPGA)为核心芯片的检测系统,用于产生所需要的矩形脉冲激励信号以及对传感器响应信号的欠采样.利用8 mm直径的电涡流线圈,对0～10 mm范围内碳钢目标靶的位移响应特性进行了测量,借助短时傅里叶变换分析了响应信号中频率成分的分布情况,同时获得了谐振频率及谐振阻尼的测量值.验证了通过脉冲激励同时获取电涡流传感器双参数检测的可行性.为研制基于电涡流效应的位移传感器及无损探伤传感器提供了一种新思路.     

用输出电感做谐振电感的软开关弧焊逆变电源

FB-ZVS-PWM变换器结合了PWM控制技术和零电压谐振技术的优点,但由于该电路借着功率开关元件的寄生电容和变压器的原边漏感形成谐振回路,只有在较大的负载电流时才能实现完全的零电压开关。本文通过在变压器副边增加两个饱和电感作为磁性开关,使输出滤波电感绐终反射到原边,参与谐振切换过程,在很小的电流下就实现了全负载下的零电压开关。上述研究结果通过计算机仿真和硬件试验得到了证实。     

PCB型Rogowski线圈电流传感器检测电路设计

介绍了PCB型Rogowski线圈的工作原理及特点,详细分析并设计了该传感器的信号处理电路,对该线圈电流传感器进行了线性度和灵敏度测试,实验结果表明:该传感器测量时线性度好,准确度较高,能满足测量要求。     

直流叠加脉冲电流波形宽频带电流传感器

提出了一种用于测量直流叠加脉冲电流波形的电流传感器。该传感器由两个磁芯组成,一个工作于磁通门状态,另一个基于罗氏线圈原理。为了将磁通门与罗氏线圈检测技术集成在一起,引入了一个反馈绕组,有效克服了脉冲磁场与直流磁场对磁芯工作状态的影响。基于理论分析制作了样机。实验结果表明,所提出的电流传感器能有效测量直流叠加脉冲电流波形:有效测量频带为340 k Hz,直流分量的测量误差为0.6%;低频段与高频段交点处的测量误差最大,最大测量误差为1.5%。     

四极杆并联振荡电子学系统和反馈控制

四极杆质谱的电场是由随时间变化的射频交变电压(RF)及直流电压(DC)分别加在两对极杆上产生的。通常射频交流电压由电感电容谐振振荡电路产生,根据电感电容的连接方式不同分为并联振荡电路和串联振荡电路。本综述主要解读并联振荡电子学系统及其反馈控制的核心技术原理。并联谐振的优势在于对射频振荡源的内阻要求不高,容许高内阻的振荡源,使电路的设计与研制更加简单;其缺点是需要采用双调谐振荡回路,在阻抗匹配方面有较高的要求。另外,并联振荡回路的升压主要依靠次级线圈与初级线圈的匝数比,因此仅适合于升压较小,即所需RF输出电压较低的场合。     

An ultralow noise current amplifier based on superconducting quantum interference device for high sensitivity applications

An integrated ultrahigh sensitive current amplifier based on a niobium dc superconducting quantum interference device (SQUID) has been developed. The sensor design is based on a multiturn signal coil coupled to a suitable SQUID magnetometer. The signal coil consists of 60 square niobium turns tightly coupled to a superconducting flux transformer of a SQUID magnetometer. The primary coil (pick-up coil) of the flux transformer has been suitably designed in order to accommodate the multiturn input coil. It has a side length of 10 mm and a width of 2.4 mm. In such a way we have obtained a signal current to magnetic flux transfer coefficient (current sensitivity) as low as 62 nA∕Φ(0). The sensor has been characterized in liquid helium by using a direct coupling low noise readout electronic and a standard modulated electronic in flux locked loop configuration for the noise measurements. Beside the circuit complexity, the sensor has exhibited a smooth and free resonance voltage-flux characteristic guaranteeing a reliable and a stable working operation. Considering a SQUID magnetic flux noise of S(Φ)(1∕2) = 1.8 μΦ(0)∕Hz(1∕2) at T = 4.2 K, a current noise as low as 110 fA∕Hz(1∕2) is obtained. Such a value is about a factor two less than the noise of other SQUIDs of the same category. As an application, Nyquist noise measurements of integrated test resistors using the current sensing noise thermometer technique are reported. Due to its high performance such a sensor can be employed in all applications requiring an extremely current sensitivity like the readout of the gravitational wave detectors and the current sensing noise thermometry.     

A traceable technique to calibrate dc current shunts and resistors in the range from 10 μΩ to 10 mΩ

A traceable to dc resistance and dc voltage National Standards measurement technique to calibrate dc current shunts and resistors in the range from 10 μΩ to 10 mΩ has been developed at National Institute of Metrological Research (INRIM) in addition to the primary reference system for low value resistors calibration. This technique is applicable in secondary and industrial metrological laboratories. It is based on a volt-amperometric method, to compare an unknown shunt with a standard one in 1:1 or 1:10 ratios. In the setup are involved: a dc current calibrator and a current generator to supply currents respectively up to 100 A and up to 1200 A, with a switch to reverse the current, two 7 1/2 digit nanovoltmeters (nVs) for the acquisition of the voltage on the standard and under calibration shunts and two Tinsley 100 μΩ and 1 mΩ standard shunts kept in mineral oil and with a cooling system. An optional variation in the procedure that can reduce the measurement uncertainties is discussed. The 2σ relative capabilities of the technique span from 6.0 × 10⁻⁶to 4.6 × 10⁻⁴. Compatibility results with the INRIM reference measurement system for low value resistors calibration are also given.     

干涉式光纤电流传感器

高压输电线中的电流测量大都采用铁芯式电流互感器。由于铁芯的非线性特性，一次测电流过大或含有高次谐波分量时，会出现磁路饱和现象，使电流互感器二次测电流数值和波形发生失真，从而引起测量精度下降。文中，设计了一种干涉式光纤电流传感器，提出了使用Rogowski线圈进行电流-电压转换，利用压电晶体实现相位调制，用迈克尔逊干涉仪进行相位检测的方法，解决了在高压端无源情况下，由电流转换的电压小的问题，提高了传感器的精度、可靠性和测量范围。     

A Magnetizer for Studying Transient Processes in Magnets over a Wide Time Interval

The magnetizer is intended for studies of transient processes in magnetic samples shaped as plates or planar films. The main element of the magnetizer is a strip line consisting of thin wires connected in series with damping resistors. The use of resistors makes it possible to reduce the eddy current decay time (and, therefore, the magnetic field settling time) to 5–6 ns and, in turn, to extend the range of durations of the processes under study and increase the spatial homogeneity of the field. The magnetization of samples is measured using a removable longitudinal sence loop. The magnetizer can be used to study a wide variety of transient processes with a duration of 0.05–100 s (in permalloy films, iron borate single crystals, garnet ferrite films with easy-plane anisotropy, etc.). The magnetizer can also be used to observe dynamic domains.     

Resonant enhancement of a passive coil-capacitance loop in eddy current sensing path

A passive resonant coupling loop was composed by connecting an inductive coil with a capacitance element in series. Without any electric connection with measurement circuits, the loop is coaxially inserted into the sensing path between the sensing coil and metallic target of an eddy current proximity sensor. When the sensor is working around the natural frequency of the resonant loop, the mutual coupling between the sensing coil and metallic target is efficiently improved. Home-made eddy current proximity sensing coils are experimentally tested in frequencies around 800 kHz. The results indicate that the equivalent inductance of the sensing coil performs more sensitively to metallic target distance. Thus the higher sensitivity and resolution of proximity sensor will be expected.     

Fabrication and characterization of a new MEMS fluxgate sensor with nanocrystalline magnetic core

This paper presents a new MEMS fluxgate sensor with a Fe-based nanocrystalline ribbon magnetic core and 3D micro-solenoid coils. The excitation coils were placed vertically to the sensing coil on the chip plane. Second harmonic operation principle was adopted in this fluxgate sensor. The total size of the fluxgate sensor was 6.25 mm × 4.85 mm × 120 μm. A simple testing system was established to characterize the fabricated devices. A band pass filter was used to pick up the second harmonic signals in the sensing coils. When excitation rms current of 120 mA and the operational frequency of 200 kHz were selected for the testing of the fabricated devices, the sensitivity of the developed fluxgate sensor was 1005 V/T in the linear range of −500 μT to +500 μT. Due to the combination of the 3D structure coils with the nanocrystalline core, relatively low sensor noise was achieved. The noise power density was 544 pT/Hz^0.5@1 Hz and the noise rms level was 9.68 nT in the frequency range of 25 mHz-10 Hz.     

Research on Microelectromagnetic Relays

A new microelectromagnetic relay is presented and fabricated based on micromachining technology, aiming at the miniaturization and high manufacturing efficiency of electromagnetic relays. This microrelay is composed of a lower magnetic circuit, a planar exciting coil, and an upper magnetic armature. A complete magnetic circuit is composed, and the “ON” and “OFF” states are controlled by the current of the exciting coil. The dimension of this microrelay is 5 mm × 5 mm × 0.4–mm. The fabrication process mainly includes lithography, sputtering, electroplating, etching, sacrifice-layer technology, etc. Electromagnetic force is calculated theoretically. The calculation results are used for the optimization design of the armature and the number of turns of the exciting coil. A microelectromagnetic relay is fabricated and the initial test results are given. The resistance of the exciting coil is about 300 Ω. The switch-on state resistance is about 1.7 Ω at an exciting current of about 50–mA. Translated from Journal of Beijing University of Technology, 2004, 30(2) (in Chinese)     

用于冲击电流测量的自积分式Rogowski线圈的研究

文中介绍了一种自制的自积分式Rogowski线圈配合示波器所组成的冲击电流测量系统的基本原理,采用标准电阻对该Rogowski线圈的测量结果进行了实验校准,并对校准实验数据进行处理.从处理结果看,该Rogowski线圈具有较好的冲击电流测量精度.     

磁流变减振器磁场特性分析及试验研究

设计了磁流变减振器磁芯磁路,建立了磁路的仿真模型,仿真研究了磁路的磁场特性,用实验的方法对仿真模型进行了验证和修正;在此基础上,建立了整个磁流变减振器的仿真模型,仿真研究了其磁场分布规律及不同参数下阻尼孔附近的磁通密度.研究结果表明,磁芯直径、工作缸壁厚、阻尼通道长度和线圈电流是影响磁场特性的主要因素,合理选择磁路结构参数可使其性能得到最大发挥.设计并制造出一种车辆单筒充气式磁流变减振器,对其进行了台架试验,得到不同电流下的减振器示功特性图,研究发现,通过调节减振器励磁线圈中的电流获得不同强度的磁场,在磁场作用下,磁流变液粘度发生变化,从而改变减振器的阻尼特性,减振器的饱和工作电流约为2A.试验验证了磁路设计的正确性,并为实现车辆磁流变半主动空气悬架控制研究奠定了基础.     

Tape-wound Rogowski coil for measuring large-magnitude pulsed currents

This paper presents design, calibration and testing of a new tape-wound Rogowski coil for measuring large-magnitude pulsed currents. The performance of the coil is tested by different impulse current waveforms up to 9 kA peak value. The coil is calibrated versus two commercial impulse-current transformers with different impulse current waveforms. The coil design is optimized to work in the differentiating mode and achieve useful bandwidth and sensitivity up to 1 MHz and 102 mV/kA, respectively. Waveform distortion of the coil output voltage is examined by using the lumped-element model to optimize the parameters of the external passive integrator. It is desired to optimize the integrator parameters and achieve the desired bandwidth without having droop and backswing. To do so, the coil frequency response is investigated by making fast Fourier transform (FFT) of the impulse current waveforms and PSPICE simulation of the lumped parameter equivalent circuit of Rogowski coil and the external integrator. Finally, it is found that the PSPICE calculated sensitivity for the optimized integrator parameters deviates from the corresponding measured one by a percentage relative error of–0.05%.     

光纤电流互感器中Rogowski线圈的设计与分析

Rogowski线圈作为传感头是光纤电流互感器的关键部分,文章分析了Rogowski线圈的测量原理和等效电路,得出了测量关系,并根据分析设计了一个Rogowski线圈。实验表明该Rogowski线圈具有良好的线性度;频率特性分析显示该Rogowski线圈有非常充裕的带宽,进而为设计高精度的光纤电流互感器奠定了基础。     

基于罗科夫斯基线圈的脉冲电流的测量

对脉冲电流的测量方法以罗科夫斯基线圈的设计过程进行了阐述，对罗科夫斯基线圈设计过程中的骨架材料以及绕线材料选择的问题，分别进行介绍，同时分析了提高罗科夫斯基线圈互感系数的方法，并通过具体的实验对脉冲电流进行了测量。     

Detecting the position of the moving-iron solenoid by non-displacement sensor based on parameter identification of flux linkage characteristics

Currently, most researches use signals, such as the coil current or voltage of solenoid, to identify parameters; typically, parameter identification method based on variation rate of coil current is applied for position estimation. The problem exists in these researches that the detected signals are prone to interference and difficult to obtain. This paper proposes a new method for detecting the core position by using flux characteristic quantity, which adds a new group of secondary winding to the coil of the ordinary switching electromagnet. On the basis of electromagnetic coupling theory analysis and simulation research of the magnetic field regarding the primary and secondary winding coils, and in accordance with the fact that under PWM control mode varying core position and operating current of windings produce different characteristic of flux increment of the secondary winding. The flux increment of the electromagnet winding can be obtained by conducting time domain integration for the induced voltage signal of the extracted secondary winding, and the core position from the two-dimensional fitting curve of the operating winding current and flux-linkage characteristic quantity of solenoid are calculated. The detecting and testing system of solenoid core position is developed based on the theoretical research. The testing results show that the flux characteristic quantity of switching electromagnet magnetic circuit is able to effectively show the core position and thus to accomplish the non-displacement transducer detection of the said core position of the switching electromagnet. This paper proposes a new method for detecting the core position by using flux characteristic quantity, which provides a new theory and method for switch solenoid to control the proportional valve.     

基于磁敏元件的寄生式时栅传感器仿真分析

传统寄生式时栅位移传感器采用线圈传输电信号,不能保证线圈本身及绕线质量,导致寄生式时栅位移传感器体积大、灵敏度低、功耗大。根据寄生式时栅位移传感器的工作原理,选择一种基于磁敏元件代替绕制线圈的方法。用ANSOFT/Maxwell对磁钢和磁敏元件的气隙磁场、磁敏元件与被测齿轮之间的距离、磁钢大小和形状进行仿真,比较分析可知3mm×3mm×2mm的长方体磁钢在气隙为3mm的情况下能够满足磁敏元件的工作要求。     

Method for calibrating a Rogowski coil of fast time response

A new method was designed for calibrating a Rogowski coil of fast time response. The method is based on the cable pulser method except that the voltage signal pick-off output was moved to a position with a distance l from the load. If 2l/v is longer than the time duration of the forward voltage pulse u(f)(t), the reflected voltage pulse u(r)(t) could be separated from u(f)(t) and directly measured. Using the formula i(t)=[u(f)(t)-u(r)(t)]/50 to calculate the primary current of the Rogowski coil, the coil could be more accurately calibrated.