加速器用无人值守数字示波器设计

为监测离子源加速器故障短路电流和电压波形,给出了一种无人值守数字示波器的方案,其硬件上基于FPGA和单片机,软件上基于LABVIEW。相比于使用泰克示波器的传统方法,该方案有性价比高、轻便、抗强电磁干扰、基于PC远距离监控故障、自动存储故障波形等优点,能良好地模拟数字示波器波形,达到无人值守的效果。     

重力加速度g的测定──数字式实时示波器的应用实验之一

数字式实时示波器具有波形存储或记忆功能，所以可以捕捉到持续时间或时间间隔很短的波形，因此用途非常广泛，这是普通模拟示波器不可替代的.下面介绍用实时示波器做一个简单的物理实验──测重力加速度g.在测重力加速度g中，当小球自由下落时，因受到距离的限制，下落时间很短，因此很难测准.而用数字式实时示波器配上简单实验装置可以解决这个问题.实验装置如图1所示，N为电磁铁，可取自旧的继电器上的电磁铁.P为小铁球，大小与乒乓球相同.S为按钮开关，按钮面积大小为1.5×1.5cm左右.E为6V直流电源.K为单刀开关.O为实时示波器.当单刀…     

用二踪示波器测计数器工作波形

在数字电路实验中,用二踪示波器测计数器的工作波形,往往不是一件容易的事。由于计数器是多个输出端,如二一十进制的计数器,输出端有四个,计数时钟脉冲输入端一个,而二踪示波器一次只能显示两个波形,本文介绍如何正确地在示波器上显示出计数器的五个工作波形,并描绘下来的测试方法。     

示波器实验的教学改革

示波器的原理和使用是大学物理实验教学的一个基础实验项目.传统的教学仅限于向学生介绍示波器显示波形的原理,测量信号电压、频率和周期等参数,以及采用利萨如图形测量待测信号频率等内容.随着科技的进步,传统的模拟示波器已经逐步被数字示波器所替代,一些高校实验项目也做了相应的调整.本课题探讨数字示波器的实验拓展,即结合压电传感器...     

隔振器对加速度开关工作性能的影响

用改装了的加速度开关（输出连续模拟信号），与两个标准传感器进行振动波形相位的比较，从而判断隔振器对加速度开关影响。试验方法是：将振动台的控制传感器作为标准传感器，安装在示波器的CHI通道进行测试；在隔振器的转接板上安装一个测试传感器，从示波器的CH2通道测试其振动波形；加速度开关的输出接在示波器的CH3通道，测试敏感元件的实际响应波形。     

将普通示波器改为慢扫描二踪数字存贮示波器的附加装置

普通示波器在显示缓慢变化的信号时不能显示为一连续波形,用长余辉示波管显示缓变信号也不够理想,而一般商品化数字存贮示波器价格昂贵(5000元以上)。本文所介绍的这种装置,采用普遍使用的数字集成电路,其成本不超过100元,且不需对普通示波器作任何改动,就可实现对缓变信号的实时显示、冻结与存贮。由于具有双通道同时显示及滚动扫描的功能,这就使对波形的比较与观察变得非常清楚明了。用这种装置对普通示波器的更新改造简单易行,并且对普通示波器的单独使用无任何影响。     

用于演示实验的电视示波器

在振动与波、电工、无线电等教学中,广泛使用各种示波器。然而在课堂演示实验中,普遍存在的一个问题是示波器的屏幕小,可见度差。为解决这一问题,我们试验成一种电视示波器:在黑白电视机上加一信号转换器,用电视机来显示各种波动信号。因此,屏幕比普通示波器大得多,图形亮度、清晰度更好,造价也比普通示波器低得多。 一、设计原理 要用黑白电视机来显示波形,关键是把要演示的波形信号变成电视机能显示的视频信号。电视机显象管电子束的扫描是固定的,有行扫描和场扫描,今以场扫描的方向作时间轴,每一行上的亮点的位置表示那个时刻输入波形的…     

用示波器测量频率三种方法的探讨

示波器是一种用途广泛的电子测量仪器,在很多科学研究中需要使用示波器,所以示波器使用的实验也是大学物理实验课中基本实验之一,要求学生能熟练掌握示波器的使用方法。示波器能观察电信号的波形,也能测量电信号幅度、周期、频率等参数,双踪示波器还可以通过波形叠加展开多种测量。本文就是针对示波器测量频率的3种方法的探讨,比较它们各自的优缺点,拓展学生的思路,更好培养学生的探索精神。     

电子开关

目前中学普遍配备的J2458型教学示波器、J2459型学生示波器都是单踪简易示波器,只能显示一个信号波形。但是在物理实验中往往需要同时观察和测量两个或两个以上的信号波形,以比较它们之间的差别,这就需要给上述示波器配备电子开关,使单踪示波器显示双踪或多踪信号。本文介绍电子开关的工作原理及使用方法,供参考。     

用数字示波器测量RC串联电路的幅频和相频特性

用数字示波器代替模拟示波器可同时准确地测量RC串联电路的幅频和相频特性。     

质点沿可自由移动的光滑凹槽的运动分析

分析了质点在可自由移动的凹槽上运动的运动平面与凹槽的交线是一般曲线的情况,给出了质点在静止参考系中运动的轨迹方程和严格等时振动的条件,求出了质点沿几种常见曲线运动的周期.     

Real-time nanometer-vibration measurement with a self-mixing microchip solid-state laser

Nanometer vibration analysis of a target has been demonstrated by a self-aligned optical feedback vibrometry technique that uses a laser-diode-pumped microchip solid-state laser. The laser output waveform, which was modulated through interference between a lasing field and an extremely weak (<- 100-dB) frequency-modulated (FM) feedback field, was analyzed by the Hilbert transformation to yield the vibration waveform of the target. Experimental signal characteristics have been reproduced by numerical simulations. Real-time vibration measurement has also been achieved with a simple FM demodulation circuit.     

MR detection of mechanical vibrations using a radiofrequency field gradient

A new method for NMR characterization of mechanical waves, based upon radiofrequency field gradient for motion encoding, is proposed. A binomial B1 gradient excitation scheme was used to visualize the mobile spins undergoing a periodic transverse mechanical excitation. A simple model was designed to simulate the NMR signal as a function of the wave frequency excitation and the periodicity of the NMR pulse sequence. The preliminary results were obtained on a gel phantom at low vibration frequencies (0-200 Hz) by using a ladder-shaped coil generating a nearly constant RF field gradient along a specific known direction. For very small displacements and/or B1 gradients, the NMR signal measured on a gel phantom was proportional to the vibration amplitude and the pulse sequence was shown to be selective with respect to the vibration frequency. A good estimation of the direction of vibrations was obtained by varying the angle between the motion direction and the B1 gradient. The method and its use in parallel to more conventional MR elastography techniques are discussed. The presented approach might be of interest for noninvasive investigation of elastic properties of soft tissues and other materials.     

接触缺陷的振动调制超声导波检测技术研究

针对常规线性超声检测方法无法实现板结构接触类缺陷(如微裂纹、脱粘等)检测问题,将超声导波技术与振动声调制技术相结合,利用稀疏分布传感器发展了一种板结构中接触缺陷非线性超声检测方法。通过低频振动改变缺陷的接触状况,使得通过接触面的高频导波信号的相位和幅值受到调制。对受低频振动调制的超声导波二维时间序列进行时频分析,由于接触类缺陷的存在,在振动调制超声导波序列的时频分布上出现明显的低频振动频率分量。利用提取出的低频振动频率下的超声导波信号,进行了结构接触缺陷成像处理。检测试验表明,基于振动声调制的超声导波缺陷成像方法可以实现结构中的接触类缺陷检测。      

窄脉冲相干激光雷达偏频锁定系统仿真研究

鉴于偏频锁定技术在激光外差探测和激光雷达等方面的广泛作用,基于可编程逻辑器件,设计了适用于窄脉冲激光外差信号的偏频锁定控制系统。在设计中,使用超高速电压比较器进行波形变换、多脉冲鉴频和大概率均值滤波进行数字鉴频,采用小步长快速控制方法进行调频,利用数模转换器和线性放大电路输出调频信号。借助信号发生器产生40ns脉宽的模拟外差信号对系统进行了仿真,实现了设计功能。对系统进行鉴频和调频测试,在40ns脉宽时鉴频误差范围为-7.5MHz～+7.7MHz。     

Fast Brillouin Optical Fiber Sensor for Distributed Dynamic Measurement Based on Differential Double-Pulse

We demonstrate a high-spatial-resolution fast Brillouin optical time-domain analysis scheme based on frequency agility and differential double-pulse for distributed dynamic measurement. The frequency-agility probe wave is obtained from the second-order sideband of modulated light by using frequency-agility microwave signal from a wideband arbitrary waveform generator. The differential double-pulse technique is proposed to improve the spatial resolution while keeping the capability of dynamic measurement. In experiment, a spatial resolution of 20 cm is achieved by using a 52/50 ns differential double-pulse, and the distributed vibration measurement is demonstrated over a 50-m Panda fiber with a maximum vibration frequency of up to 50 Hz. With only five averages, the standard deviation of the strain accuracy is of 14 μV.     

Model for modulated and chaotic waves in zero-Prandtl-number rotating convection

The effects of time-periodic forcing in a few-mode model for zero-Prandtl-number convection with rigid body rotation is investigated. The time-periodic modulation of the rotation rate about the vertical axis and gravity modulation are considered separately. In the presence of periodic variation of the rotation rate, the model shows modulated waves with a band of frequencies. The increase in the external forcing amplitude widens the frequency band of the modulated waves, which ultimately leads to temporally chaotic waves. The gravity modulation, on the other hand, with small frequencies, destroys the quasiperiodic waves at the onset and leads to chaos through intermittency. The spectral power density shows more power to a band of frequencies in the case of periodic modulation of the rotation rate. In the case of externally imposed vertical vibration, the spectral density has more power at lower frequencies. The two types of forcing show different routes to chaos.      

Vibro-modulation and Guided wave techniques for contact defect detection in plate

A nonlinear acoustic technique for detection of contact defects in plates was developed associating guided waves with vibro-modulation techniques.The low frequency vibration varies the interface area within the contact defect;then the amplitude and phase of high frequency guided waves reflected from the contact defect will be modulated.Due to the exiting of contact defects,there was obvious low frequency component in the time-frequency distribution of modulated guided wave series.Furthermore the nonlinear responses at frequency of vibration were extracted out and used for defect imaging.It was shown that the nonlinear guided wave imaging method based on vibration modulation can effectively characterize and locate the nonlinear contact defects.     

基于二维声子晶体的大尺寸夹心式换能器的优化设计

夹心式换能器应用极为广泛,但当其横向尺寸过大时,存在耦合振动,影响其辐射面的位移分布.本文通过在大尺寸夹心式换能器的前盖板中加工周期排列的槽,来形成一种二维声子晶体结构.随后,采用有限元法对基于二维声子晶体的大尺寸夹心式换能器的振动传输特性、共振频率以及发射电压响应进行仿真模拟,讨论了开槽高度和开槽宽度对其带隙、共振与反共振频率、带宽以及辐射面位移分布的影响.研究结果表明,通过在大尺寸夹心式换能器中应用声子晶体结构可对其进行优化设计.当大尺寸夹心式换能器的工作频率位于其带隙范围内时,二维声子晶体结构能有效地抑制其横向振动,从而改善换能器辐射面位移分布的均匀程度.此外,在大尺寸夹心式换能器的前盖板中加工二维声子晶体结构,能有效提升换能器的带宽,进而拓宽大尺寸夹心式换能器的工作频带.     

一种光纤通信系统中非线性克尔效应抑制新方法

本文从非线性薛定鄂方程出发,提出了一种全光学的相位预加重来抑制非线性克尔效应的新方法,通过在发射端将输入光脉冲的初始相位上叠加一个平方相位值,改变光脉冲的初始相位值,从而提高光脉冲在光纤传输中抗非线性克尔效应能力.通过理论研究,仿真分析以及实验验证了该方法的可行性,实验验证在接收端可以提高误码率2个数量级以上.在长距离大容量光纤通信系统中有很好的应用前景.