示波器文献综述

示例示波器的原理及应用论文1. 引言示波器是一种常用的电子测量仪器，用于检测和显示电压随时间变化的波形。

它广泛应用于电子、通信、无线电等领域。

本文将介绍示波器的基本原理及其在实际应用中的一些典型场景。

2. 示波器的基本原理示波器的基本原理是根据输入信号的变化来控制电子束的偏转，从而在屏幕上显示出相应的波形。

示波器主要由以下几个部分组成：- 垂直放大电路：用于放大输入信号的幅度，以便能够显示在屏幕上。

- 水平放大电路：用于控制扫描线的速度，以便能够正确显示信号的时间变化。

- X-Y放大电路：用于将两个输入信号进行叠加显示，常用于观察两个信号之间的相位关系。

- 触发电路：用于设置示波器的触发条件，保证稳定的波形显示。

3. 示波器的应用场景3.1 电子设备维修示波器在电子设备维修中起着重要的作用。

通过连接示波器到待测设备的电路上，技术人员可以通过观察波形来判断问题所在。

例如，当出现频率不稳定的情况时，示波器可以帮助定位到频率问题的源头。

3.2 信号分析示波器可以用来对信号进行分析。

通过调整示波器的垂直和水平放大倍数，可以观察到信号的频率、幅度、相位等特征。

这在电子通信领域中非常有用，例如在无线电设备调试中，可以使用示波器来观察信号的无线电频率和调幅等信息。

3.3 教学实验示波器也被广泛应用于电子实验教学中。

学生可以通过连接示波器到实验电路上，观察和分析实验中的波形变化。

这有助于学生理解电子原理和实验过程。

4. 示波器的使用注意事项在使用示波器的过程中，需要注意以下几点： - 示波器的输入信号范围不能超过设备规定的最大输入范围，否则可能会损坏设备。

- 示波器的触发条件需要正确设置，以保证稳定的波形显示。

- 连接示波器到待测电路时，需要注意正确的接地方式，避免出现误差。

5. 结论示波器是一种重要的测量仪器，具有广泛的应用前景。

本文介绍了示波器的基本原理和一些常见的应用场景，以及在使用示波器时需要注意的事项。

毕业设计开题报告电子信息工程基于LABVIEW的虚拟示波器设计[前言]虚拟仪器[1]技术就是利用高性能的模块化硬件，结合高效灵活的软件来完成各种测试、测量和自动化的应用。

自1986年问世以来，世界各国的工程师和科学家们都已将LABVIEW图形化开发工具用于产品设计周期的各个环节，从而改善了产品质量、缩短了产品投放市场的时间，并提高了产品开发和生产效率。

使用集成化的虚拟仪器环境与现实世界的信号相连，分析数据以获取实用信息，共享信息成果，有助于在较大范围内提高生产效率。

虚拟仪器提供的各种工具能满足我们任何项目需要。

20年来，无论是初学乍用的新手还是经验丰富的程序开发人员，虚拟仪器在各种不同的工程应用和行业的测量及控制的用户中广受欢迎，这都归功于其直观化的图形编程语言。

虚拟仪器的图形化数据流语言和程序框图能自然地显示您的数据流，同时地图化的用户界面直观地显示数据，使我们能够轻松地查看、修改数据或控制输入。

虚拟仪器的出现使测量仪器领域的一个突破，它彻底改变了传统的仪器观，从根本上更新了测量仪器的概念，带给了人们一个全新的仪器观念。

虚拟仪器代表着测量仪器发展的最新方向和潮流，是未来仪器产业发展的一大趋势[2][3]。

[主题]1.仪器发展过程1.1 传统硬件仪器20世纪30年代初，HP公司创始人、斯坦福大学的Hewlett和Packard在现今的硅谷研制出了第一台信号产生器。

传统硬件仪器经历了大半个世纪的发展，经历了从模拟式到数字式，到现今智能化仪器的发展历程。

传统硬件仪器由决定仪器功能、性能和技术指标的电子板卡、带有插槽的底盘、装有各类控件的面板、显示器和机箱等五部分构成。

传统硬件仪器是硬件或以硬件为主的仪器，即使是智能仪器，其中固化的软件也只是辅助性的。

传统硬件仪器是一个封闭系统，一经厂家制造完毕，不能随意改动，灵活性较低。

无论是对技术的进步还是对市场的需求，其响应速度都比较慢，这在很大程度上阻碍了仪器科学和仪器。

毕业设计文献综述院（系）计算机科学与信息工程学院专业年级 2007级电子信息工程1班学生姓名吕宽学号 2007132104 指导教师陈明杰日期2011年6月1日数字存储示波器的设计吕宽(重庆工商大学计算机科学与信息工程学院电子信息工程2007级1班)摘要随着科学技术的发展，作为常用的检测工具，示波器的面貌也焕然一新。

由于数字技术的采用，示波器成为集显示、测量、运算、分析、记录等各种功能于一体的智能化测量仪器。

数字存储示波器(DSO)将取代模拟示波器。

目前，国内具有自主知识产权的数字存储示波器产品还非常少，高昂的价格阻碍了数字存储示波器在生产和试验中广泛的应用。

在研究剖析数字存储示波器产品工作原理的基础上，本文利用NIOS II设计示波器，并详细论述了其设计和实现过程。

关键词数字存储示波器 NIOS IIABSTRACT With the development of science and technology, the oscilloscopes, as common instruments, have made great progress. With digital technology, the oscilloscopes have become a kind of intelligent instrument with functions: waveform display, parameter measure,detecting,analyze, storage, and so on. The Digital Storage Oscilloscope (DSO) will replace Analog Oscilloscope. At present, domestic DSO product's type, which has our own independent property right, is too few. The DSO is hindered to apply wildly in our production and test by high price. On the basis of the analysis of DSO's fundamental principle, the design and implementation of a kind of portable digital storage oscilloscope system was discussed in detailed in the dissertation.KEY WORDS DSO NIOS II目录1、绪论 (5)1 .1、示波器简介 (5)1.2课题背景及主要工作 (6)2、硬件设计 (8)3、软件设计 (9)4、现阶段国内外发展情况 (10)5. 数字存储示波器的将来 (11)6. 结语 (12)参考文献： (13)1、绪论1 .1、示波器简介人类在认识自然和改造自然的过程中，必定要进行测量活动。

示波器技术发展研究论文（11篇）篇1：示波器技术发展研究论文篇2：示波器技术发展研究论文电子测量的主要问题是解决“信号存在”和“信号定量分析”。

对复杂信号的存在检测和定量分析是示波器的首要任务，DPO正是在解决这一测量问题中发展起来的一种新型示波器技术，在某种程度上，展现了示波器技术的发展趋势。

(1)完全数字化设计数字荧光示波器优于模拟、胜于数字的突出功能很大程度上是因其采用了数字荧光技术。

“信号存在”是电子测量的基础，只有证实了信号的存在才能对其进行定量分析，ART示波器的余辉显示在证实信号存在方面虽具有突出的优势，但DPO不是简单地仿真ART示波器的灰度显示功能，是以数字技术为基础构建的具有模拟效果的一种新型示波器显示方式(信号数字化-图形化-显示)。

全数字化设计突破传统模拟仿真的旧模式，创建了以数据处理技术为基础的仪器设计新概念。

(2)虚拟与现实的有机结合数字荧光示波器的核心部件DPX数字成像处理器，其关键技术是硬件三维动态数据库的读写。

由于DPO的显示方式同计算机的显示方式完全相同，是基于计算机结构的仪器，如果计算机的速度足够快，完全可以由虚拟仪器来实现。

DPO正是基于虚拟仪器原理，通过专用芯片完成大量的数据处理功能，进而构成的仪器系统。

这类仪器因其运算速度快具有实时性的特点，它的便携性克服了虚拟仪器不利现场使用的缺点，体现了现代仪器的发展方向。

篇3：建筑工程技术发展研究论文建筑工程技术发展研究论文1建筑工程的现状1.1建筑工程的发展现状虽然我国在严格控制着人口的增长，但是我国人口的增多已经是一个不可回避的问题，土地的使用满足不了人们的需求，因此，建筑出现了。

建筑能够减缓这一问题。

它占用了相对较小的土地面积从而容纳了大量的人口，解决了人们的居住问题。

对于高层的建筑，建造时的危险系数很高。

一般的低层建筑的地基方面的要求不会过高，而建筑的所有结构都是在地基之上建造而成，因为许多建筑的高度大，因此，需要的材料多，受到外界因素的可能性就相对很大。

示波器技术发展研究论文示波器是一种广泛应用于电子技术领域的仪器，用来测量、观察和分析电信号的特性。

示波器技术的发展对电子行业的发展起到了重要的推动作用。

本文将对示波器技术的发展进行研究，并对其影响进行分析。

首先，示波器技术的发展可以追溯到20世纪初。

最早的示波器是机械示波器，它通过机械方式将电信号转化为机械运动，然后通过光电检测方式来观察信号的特征。

然而，机械示波器的速度和精度有限，无法满足后续电子技术的发展需求。

随着电子技术的进一步发展，电子示波器逐渐取代了机械示波器。

电子示波器采用电子方式来观察信号，具有更高的速度和精度。

最早的电子示波器使用电视管来显示信号，但是由于电视管对观察的信号频率、幅度范围有限，后来的示波器采用了CRT显示技术，从而大大提高了观测信号的能力。

随着半导体技术的进步，示波器的集成化程度也得到了提高。

现代示波器采用了高速ADC、FPGA和DSP等先进技术，使得示波器具有更高的采样率、更大的存储容量和更强的信号处理能力。

另外，现代示波器还提供了多种触发模式、计量功能和自动测试功能，可以满足不同应用场景的需求。

示波器技术的发展对电子行业的发展起到了重要的推动作用。

首先，示波器的高速采样和存储能力使得工程师可以更准确地分析和解决电路中的问题，提高了电路设计的效率和质量。

其次，示波器的自动测试功能可以大大简化测试流程，提高测试的自动化程度和效率。

此外，示波器还广泛应用于电子制造、通信、医疗、教育等领域，为这些行业的发展提供了重要的支持。

然而，当前示波器技术仍存在一些挑战和问题。

首先，示波器的采样率和存储容量已经达到了极限，难以满足未来更高频率和更复杂信号的观测需求。

其次，示波器的尺寸和功耗仍较大，不方便携带和使用。

最后，示波器的操作和分析功能仍有一定的限制，需要进一步完善和提高。

综上所述，示波器技术的发展对电子行业的发展起到了重要的推动作用。

随着电子技术的不断进步，示波器技术也在不断发展和完善。

示波器作为一种基础的测量仪器，能直接观察电信号波形，也能测量电信号的电压和频率等。

通过将信源信号的直观再现的方式，将信息及时准确地传递给使用者，在当今社会各个方面起着非常重要的作用。

在医疗领域里，示波器用以采集人体信号，如心脏脉冲和神经元电脉冲，在任意波形发生器上进行回放，可以方面疾病的检查以及观测人体健康的情况；在工业生产领域，示波器的捕获特殊信号，加之其拥有多种触发方式利于捕捉特定波形，为解决生产效率与一致性问题，实现最重要的技术之一的自动化控制，起着决定性作用；在科学研究领域，示波器对于各种模拟或数字的的信号的采集，高速动态波形的显示，各类数据（如频率、峰峰值、脉宽等）准确测量，将实验情况及数据提供给科学研究者们方便其研究。

示波器因其直观准确地测量显示能力，已经基本被普遍应用于各个高校电子类或物理类实验室中，在测量和分析上成为老师和学生们的一大帮手。

示波器诞生于1933，到如今也已经有了80多个年头的历史了。

它随着社会和科技的发展，逐渐地由电子管向前发展，在经过了半导体化、广带域化的时代之后，再过度到到跟近代科技紧密联系的数字化、多机能的发展时代。

一支示波管、一个电源、一个简单的扫描电路，依靠着三样器件就可以组成一台示波器，这也是世界上的第一台示波器的组成方法，但其因组装简单的缘故，故而它的功能也是相对地有限，仅仅可以提供给人们用以观察信号，除此便再没有其他的功能。

战争带来的是世界的破坏，然而许多科学技术也在是战争中得以进步，第二次世界大战有了雷达的出现，而对于雷达技术的研究与发展，不得不利用到示波器，也就是在这一时期，示波器的电路结构及其相应的硬件指标得到了突飞猛进的发展，示波器的这一大发展同样对当时的又一前沿科学技术——无线电通讯技术提供了研究上的极大的帮助和支持，此时的示波器已经能够进行信号的定量测量，泰克开发的带宽达10MHz的同步示波器便是这一时期的产物，并且成为近代示波器的基础代表。

示波器的介绍和使用示波器是一种图形显示设备，它描绘电信号的波形曲线。

这一简单的波形能够说明信号的许多特性：信号的时间和电压值、振荡信号的频率、信号所代表电路中“变化部分”信号的特定部分相对于其它部分的发生频率、是否存在故障部件使信号产生失真、信号的DC 成份和 AC 成份、信号的噪声值和噪声随时间变化的情况、比较多个波形信号等。

示波器的发展初期主要为模拟示波器，模拟示波器要提高带宽，需要示波管、垂直放大和水平扫描全面推进。

数字示波器要改善带宽只需要提高前端的A/D 转换器的性能，对示波管和扫描电路没有特殊要求。

加上数字示波管能充分利用记忆、存储和处理，以及多种触发和预前触发能力。

中期数字示波器首先在取样率上提高，从最初取样率等于两倍带宽，提高至五倍甚至十倍，相应对正弦波取样引入的失真也从100%降低至3%甚至1%。

其次，提高数字示波器的更新率，达到模拟示波器相同水平，最高可达每秒40 万个波形，使观察偶发信号和捕捉毛刺脉冲的能力大为增强。

再次，采用多处理器加快信号处理能力，从多重菜单的烦琐测量参数调节，改进为简单的旋钮调节，甚至完全自动测量，使用上与模拟示波器同样方便。

最后，数字示波器与模拟示波器一样具有屏幕的余辉方式显示，赋于波形的三维状态，即显示出信号的幅值、时间以及幅值在时间上的分布。

1示波器器的使用方法示波器种类、型号很多，功能也不同。

数字电路实验中使用较多的是 20MHz 或者 40MHz 的双踪示波器。

这些示波器用法大同小异。

本文不针对某一型号的示波器，只是从概念上介绍示波器在数字电路实验中的常用功能。

1.1 荧光屏荧光屏是示波管的显示部分。

屏上水平方向和垂直方向各有多条刻度线，指示出信号波形的电压和时间之间的关系。

水平方向指示时间，垂直方向指示电压。

水平方向分为 10 格，垂直方向分为 8 格，每格又分为 5 份。

垂直方向标有 0％，10％，90％，100％等标志，水平方向标有 10％， 90％标志，供测直流电平、交流信号幅度、延迟时间等参数使用。

摘要：随着计算机技术的飞速发展，虚拟仪器技术逐渐成为电子测量领域的重要发展方向。

本文针对虚拟示波器技术进行了深入研究，分析了其在现代电子测量中的应用及发展趋势，旨在为我国虚拟仪器技术的发展提供参考。

一、引言示波器是电子测量领域的重要仪器，用于观察和测量电子信号。

传统的示波器存在着体积大、功能单一、操作复杂等问题。

虚拟示波器作为一种新型的电子测量仪器，具有体积小、功能丰富、操作简便等优点，逐渐成为电子测量领域的研究热点。

二、虚拟示波器技术原理虚拟示波器是基于虚拟仪器技术设计的一种电子测量仪器。

它利用计算机软件模拟传统示波器的功能，通过数据采集卡等硬件设备采集信号，并在计算机屏幕上显示波形。

虚拟示波器的主要技术原理如下：1. 数据采集：通过数据采集卡将模拟信号转换为数字信号。

2. 数字信号处理：对采集到的数字信号进行滤波、放大、采样等处理。

3. 波形显示：将处理后的数字信号在计算机屏幕上以图形形式显示。

4. 操作界面：提供用户友好的操作界面，方便用户进行测量和控制。

三、虚拟示波器在现代电子测量中的应用1. 信号分析：虚拟示波器可以对信号进行实时分析，如频率、幅度、相位等。

2. 故障诊断：通过虚拟示波器观察电路故障信号，快速定位故障点。

3. 信号发生：虚拟示波器可以生成各种波形信号，用于测试电路性能。

4. 测试与校准：虚拟示波器可以用于测试其他电子测量仪器的性能，实现校准。

四、虚拟示波器技术发展趋势1. 高性能：随着计算机硬件技术的不断发展，虚拟示波器的性能将得到进一步提升。

2. 智能化：虚拟示波器将结合人工智能技术，实现自动识别、故障诊断等功能。

3. 网络化：虚拟示波器将实现远程测量和控制，提高测试效率。

4. 便携化：虚拟示波器将朝着小型化、便携化方向发展。

五、结论虚拟示波器技术在现代电子测量领域具有广阔的应用前景。

随着计算机技术和虚拟仪器技术的不断发展，虚拟示波器将在性能、智能化、网络化等方面取得更大的突破。

虚拟示波器外文翻译文献综述(文档含中英文对照即英文原文和中文翻译)外文：A DAQ card based mixed signal virtual oscmoscopeAbstractComplex signals find many applications in SONAR, RADAR，Echo Location Systems and for studying the resonant frequencies. Digital StorageOscilloscopcs(DSO) is used these days for acquisition and display of routine signals. This instrument, found in every measurement laboratory, though potent in displaying simple periodic waveforms like sinusoids fails when frequency-varying time signals are applied, This problem surfaces because the underlying technique of oscilloscope used to trigger the waveform does not acquiesce with complex signals like chirp. Ready solution to this problem is the mixed signal oscilloscope. This is a costly solution and small laboratories cannot afford to have the costly instruments. In this paper, a cost effective DAQ card based mixed signal virtual 0scilloscope is proposed to study the complex signals. An intelligent technique, Weighted Hamming Distance (WHD) algorithm was used to accurately trigger the complex waveforms. Also for frequency domain analysis, Joint Time Frequency Analysis(JTFA)techniques were used. A LabVlEW'TM based virtual instrument was designed and developed with a capability to acquire, display and analyze the triggered signal. The integrated programming language LabVIEWTM was chosen as it offers many simple ready to use functions. In a way the proposal offers a cost effective, fast and flexible solution to treat the complex signals. The need to create such solutions is the consequence of costly hardware systems. The deficiency of conventional hardware. Scheme for the virtual oscilloscope for complex signals with some real time experimental results are presented in this work.Kevywords: Virtual instrumentation,Chirp signal,Data acquisition,Triggering, Complex signals, JTFA1.IntroductionFor the last two decades there has been a tremendous progress in computer technology. Measurement domain is no longer left unaffected. The way measurements are being done is totally revolutionized. Computer based measurement or say virtual instrumentation is gradually replacing the costly bench top instrumentation as it offers flexible,fast and cost effective solutions. Various classical instrumentation systems namely Oscilloscope, Multimeters and Spectrum analyzers ect. are almost phased out by their counter part virtual instrumentation. Our research extends the trend and demonstrates the developmen of the computer based mixed signal digital oscilloscope.Conventional signals such as the sinusoids have a constant frequency and the amplitede only varies with time throughout the signal definition. On the other hand, complex signals can be defined in this context as signals in which all the parameters vary. Fig.1 shows a typical complex signal i.e. Linear Chirp.Variation of amplitude and frequency with time can easily be understood by having a look at the signal. This requires a visually stable display of signal. The complex signal offers challenges f'or acquisition, display an analysis. Even the conventional modern age DSO is not capable of displaying and analyzing complex signals because these instruments employ simple triggering technique like level trigger. The conventional technnique of voltage trigger apparently fails when complex signals like chirp are analyzed on DSO. This is due to the very fact that these instruments consider chirp as a conventional sine wave and trigger for each cycle of the sine wave instead of triggering for the complete chirp cycle. This analysis of the chirp signal as several sine waveforms of different frequencies leadsthe DSO to display them as sinusoids in quick succession. As this rapid change occues at a very high rate and because of human eye not registering events occurring faster than 1/20th of a second the display appears as several overlapped sine waves. In the recent work[1], a new triggering technique was proposed for the complex signals based on WHD. Subsequent sections present the solution to the problem. For analysis of the complex signals in frequency domain JFFA technique is utilized and implemented[2-6].DSO uses the level trigger to display the waveform applied to it. This leads to trigger interval and the number of samples for this trigger interval is computed and these numbers of samples are display. The DSO considers the interval as the fundamental time period of the whole waveform and thus takes tbat much samples from its buffer and starts displaying it in quick succession. With simple waveform like a sine wave, level trigger can achieve stable display because trigger interval contains same number of cycles. This is shown in Fig. 2a.Now for the complex signal as shown in Fig.2b, level triggering produces a trigger interval having variable number of cycles for the same number ofsamples/time resulting in a visually unstable display.The actual trigger interval should be one complete cycle for a chirp signal as indicated in Fig. 2c. Having done this the repeated chirp signal for this time durationwill be displayed without any overlapping components as long as the entire time period is displayed.To observe the shortcomings experimentally in display of complex signals on the oscilloscope Tektronix dual channel signal generator AFG-3022 (250 MS/s, 25 MHz) was used to generate a chirp signal by choosing the sweep mode to sine waveform with its frequency varying linearly with respect to time. This signal was fed to TektronixTDS-2022 (2 GS/s, 200MHz) dual-channel DSO. The overlapping display as shown in Fig. 3 was observed.2. Intelligent method of triggeringAccurate triggering lies solely on correct identification of the time period of waveform under consideration. For this purpose, pattern recognition scheme was implemented to identify the pattern in the signal [1] and thus obtain the time periodof one complete cycle of the chirp. First, a fixed number of samples N are taken as reference pattern. Then the signal is shifted by one sample to form the test pattern. This pattern is then tested for its closeness' to the reference pattern. Closeness' can be defined as the distance by which test pattern is away from reference pattern.WHD is used as the decision function for closeness. Hamming distance is defined for two binary vectors as the number of different' bits are given their vectors. In WHD the different bits are given their binary weighting according to the bit position and their weights according to the bit position and their weights are summed up. WHD of two binary n bit number x and a is given byIf X and A are two binary vectors of n-bits element, then WHD for these two vectors is computed by summing up the element by element WHD and is given byFor a vector of dimension N, the samples are shifted N times and its closeness is computed at each shift.When these computations are done, the difference洫in the signals is found to be minimum (ideally zero when no noise) when the cycle repeated itself. Following are the major steps involved and implemented for intelligent trigger mechanism.1. Acquiring the long enough signal using DAQ card and to convert the decimal values of samples into binary form.2.A fixed number(N) of binary samples are stored in array. The stored samples are shifted by a fixedc number of samples, n (=1,inthis case).3. The original saved samples and the shifted samples are XORed bit-by-bit.The result is then multiplied by a factor of 2, where I represent the position of bit.4.The summation of all the resulting values gives the WHD for nth shifts.5.A plot of WHD vs. n is made and the minimum is calculated by peak detection method. The difference between two successive minima is the trigger interval in number of samples.6. The number of samples multiplied by the sampling rate results in trigger interval (in seconds).As a test case WHD algorithm is implemented for the following triangular waveforrn in Fig.4.The waveform is sampled at 8 points per eycle. Each sampled value is 3 bit length.The step by step implementation is given below.WHD waveforrn is plotted using WHD(1), WHD(2), …, WHD(8), and the location of the minima gives the triggering interval. Fig.5 shows the WHD waveform also clearly indicating the trigger interval at 8th sample.The WHD VI(Fig.6) was developed for this task. It takes the waveform, whose triggering interval is to be found, and the no of samples, on which computation is to be done, as input and outputs the sample at which minima occurs along with the value of minima and the WHD waveform. For typical chirp signal WHD waveform is obtained as shown in Fig.7. The number of samples between two consecutiveminima is equal to the number of samples in one cycle of the waveform. The product of the number of samples with the sampling interval is the triggering interval of the input signal. Thus, the virtual instrument could also display complex waveforms with considerable aese. Fig.7 shows triggering interval of 5 cycles.3. Frequency domain analysisFor simple signals the frequency analysis is performed by traditional tools like FFT. For such signals the Fourier Transform works well as their frequency components remain constant throughout the signal existence and hence there is no need for the time-frequency relationship. In case of complex signals the frequency varies with time. FFT fails to analyze these signals as it gives information about the frequency and its amplitude. Time information is lost.In order to overcome this difficulty, there are JTFA tools iike Short Time Fourier Transform(STFT) and Wavelet Transform. These are implemented for the signals under consideration.The STFT is a modified form of Fourier Transform. In this technique the signal is rnultiplied with a window function and their product's Fourier Transform (2).The main principle behind this technique is that the window function(w) breaks down the signal into segments of small finite durtion. The frequency component of the signal during this segment is assumed to be constant. By computing the Fourier Transform for this segment the frequency vs. amplitude information is obtained. Then the window is moved to another segment by a step having the same duration as the previous one giving the frequency component for that segment. Thus the frequency for different time intervals gives time-frequency relationship.However, there is a disadvantage with this tecnique. The size of the window function used is fixed, thus STFT will have same resolution for low and high frequencies. Resolution is the certainty by which one can determine time or frequency information. It is generally seen that a larger window leads to better frequency resolution and a small window leads to better time resolution. Thus, it depends upon the user whether he wants frequency or time resolution. Even if there is a need for change of resolution, the user has to do the same manually.To overcome the resolution problern, a more advanced technique called Wavelet Transform is used these days. In this the window size can be altered, using a scaling parameter a. The equation for Wavelet Transform is given as wherea is the scaling parameter,b is the translation parameter,x(t) is the signal to beanalyzed andis the wavelet functionThe wavelet function <(t) is known as the mother wavelet．Its scaled and time shifted versions are known as the daughter wavelets. These daughter wavelets having varying size offer different frequency and time resolutions at different frequencies. The scale parameter a represents the freequency component in an inverse relation. Thus the valuc of scale is inversely proportional to frequency component.Initially the wavelet function has scale a=1and is placed at the starting of thesignal. The wavelet transform and thus the frequency component of that segment. Then the wavelet function is moved by b steps and the wavelet transform is computed for that segment. This procecdure is continued till the end of the signal. Thus Wavelet transform for a=1 and all the time steps till the end of signal gets computed. Similarly the wavelet function is again placed at the start of the signal but with changed value of scale a. The procedure is continued till the Wavelet transform for each scale and time step combination has been computed.It can be observed that the computation of Wavelet Transform leads to a lot of redundancy.To reduce the redundancy, the scale values and the time steps can be linked using dyadic sampling. a= 2" and b=k 2' where n and k are integers. This leads to reduction in redundancy. This is called Discrete Wavelet Transform(DWT).4. ImplementationA DAQ card based virtual instrument was designed and developed inLabVIEW TM programming environment. This virtual instrument has the capability to generate intelligent software trigger as described above for complex waveforms like chirp. The main decisionns during design of the virtual instrument are: choosing the data acquisition card and, what is equally important, choosing the set of features the instrument should offer. The choice of the data acquistion card has a great influence on the efficiency of the whole instrument[7，8].Particular DAQ cards are differentiated by price and, the specification it offers.A low cost NIPCI-6035E, 16bit, 200KS/s card was chosen. The hardware was programmed at maximum sampling rate. A separate problem is designing software, which, in that case, is the main part of instrument design phase. The major features of the developed virtual instrument are:The capability to acquire and process simple and complex waveforms.Dual channel mode: The instrument is capable of displaying two inputs simultaneously and can perform simple math operations between the two.Auto set: Runs the WHD code to re-compute the trigger interval for the new signal and thus achieve a stable display. In case, the two inputs do not have the same frequency, the LCM of the trigger intervals of A and B is found to so that integral number of cycles of both the channels can be shown simultaneously.Time domain measurements: The signal being displayed in time domain are measured on various parameters-Amplitude-Peak to peak -Mean(DC) -RMSFig. 9. The results of wavelet transrorm implemented in the virtual instrument.(Channel A analyzing sine signal and Channel B analyzing a chirp signal). Frequency Domain Aalysis: The plot of Magnitude vs. frequency, Phase vs. frequency and the facility to choose the windowing function.STFT based Joint Time Frequency Analysis (JTFA): The spectrogram with the additional choices of the plotting the graph with scale in decibels, windowing functions and the window length for STFT analysis.Wavelet based Joint Time Frequency Analysis(JTFA)：The scalogram which plots scales vs. time steps, choice of time-frequency sampling parameters like time steps and scales and the choice of wavelet functions.For the frequency domain analysis, DSP toolkit available with LabVIEW softwarewas utilized. Standard functions are available in the toolkit. The virtual instrument thus developed is intelligent as it takes different actions with different signals contrary to a digital storage oscilloscope. Trigger implemented enables us to obtian the correct value of the time period and a stable display. Analysis of complex signals can also be performed using this instrument. Fig.8 shows the front Panel of the virtual instrument showing Time-domain measurements. Fig.9 shows the time frequency relationship on both the channel B analyses the chirp signal. As seen clearly the chirp signal shows the varying frequency with time.5. Limitations of developed virtual instrumentSamples for few cycles are required to determin the triggering interval. One need to optimize tbe appropriate sampling rate and the number of samples to be processed. The processing time taken by the WHD technique is directly proportional to the number of samples and hence to the sampling rate as the higher sampling rate leads to the more number of samples per cycle. The time required to compute trigger also depends upon the speed of the computing system. For large amount of data (if high sampling rates us fixed), computationally heavy WHD algorithm and other features for more analysis, the butter might overflow leading to loss of data. Every time the input waveform is changed user has to do retriggering.6. Conclusion and discussionSuccessful development of the virtual instrument with the capability of acquiring, displaying and analyzing complex signals is done. The instrument over comes the shortcomings of the DSOs, found commonly in laboratories, in achieving stable display for complex signals. The developd instrument is cost effective and flexible in nature and had the large number of features to choose from. The computer towards the measurement systems. The VI developed is expected to go a long way in the instrumentation area.基于混合信号的数据采集卡的虚拟示波器摘要：复杂的信号在声纳、雷达、回声定位系统和谐振频率的研究中有多种应用。

文献综述测试仪器大体经历了模拟仪器、数字化仪器、智能仪器三个阶段，其功能主要由硬件的形式存在。

这种框架式的结构决定了传统仪器只能有仪器厂家来定义、制造，而用户无法随意改变其结构和功能，即使后来出现的数字化仪器、智能仪器，虽使传统的测试精度提高、功能增强，但仍未改变传统仪器的那种独立使用、手动操作。

任务单一的模式，而且与其他仪器的链接也受到限制。

所以出现了虚拟仪器。

(一)课题研究背景及现状在20世纪80年代，个人计算机技术不断发展，虚拟仪器飞速发展，利用计算机系统的数据处理能力强，传输存储方便及其组件灵活，易于扩展的特性，使现在的测试仪器的速度、功能有了很大的突破。

而其可以方便地进行维护和升级，伴随计算机的发展，20世纪末美国国家仪器公司(National Instruments Corporation..NI)提出了虚拟仪器的概念。

虚拟仪器就是利用计算机及其软件技术，来控制相应的与计算机连接的具有仪器功能的硬件，完成对输入、输出信号的采集、控制、数据分析和显示，实习传统仪器的所有功能。

它具有良好的集成性、开放性、灵活性和可扩展性。

它的基础就是计算机系统，核心是软件技术。

虚拟仪器打破了传统仪器由厂家定义、用户无法改变的模式，降低了系统开发和维护的费用，加快了技术更新速度，缩短了系统组件时间[1]。

初期美国国家仪器公司提出的虚拟仪器利用计算机本身的总线，将数据采集卡直接插入相应的总线扩展槽内。

1978年，美国5家测试仪器公司(Hewlett-Packard,Colorado Data System,Wavetek,Tekronix,Racal-Danan)制定的开发式、模块化仪器总线标准VXI即IEEE 1115。

VXI系统组件和使用比较方便，有其是组件成大、中规模自动测试系统以及对速度、精度要求较高的场合，但其性价比不高，限制了不少用户。

1987年，IEEE 488总线问世，实现了将14太仪器由GPIB总线联机成为一个系统。