虚拟数字存储示波器毕业论文中英文资料外文翻译文献

虚拟数字存储示波器毕业论文中英文资料外文翻译文献 虚拟数字存储示波器中英文资料外文翻译文献 Virtual-digital storage oscilloscope Virtual digital storage oscilloscope-the structure and composition:Virtual digital oscilloscope PXI bus from a multi-functional data acquisition card and the corresponding software. They will be installed on a PC running Windows, constitutes a powerful can store digital oscilloscope. Data Acquisition The design of NI is used by the company's multi-purpose data acquisitioncardPXI-6670E, its main functions are as follows: 64-way single-ended / 32-way differential analog input; 12 accuracy; 1.25 MSPS sampling speed; 1.25 MSPS disk write speed ; ? 0.05 ~ ? 10V input range; two-way 12 analog outputs; eight digital I/O.two-way 24 counter /timer. Functional equipment In this case virtual digital oscilloscope with real-time data acquisition, spectralanalysis and window treatment and filtering capabilities. In the virtual digital oscilloscope main panel on data collection and analysis of the spectrum, and window processing, filtering and other function keys, according to the corresponding button we can enter into the appropriate sub-panel. Software Design and Implementation Virtual digital oscilloscope software design based on the use of C-language programming environment LabWindows / CVI. LabWindows / CVI support numerical type, Boolean, and the string of text, and other data types, but the biggest advantage is through dialog forms of interactive operations generate standard C code. In addition LabWindows / CVI provides a very rich debug tools, including single-step, breakpoints, variable view, monitor window, and so on, these features make the adjustment process has become more vulnerable. The main function modules Virtual digital oscilloscope mainly by the software control signals the completion of the acquisition and display processing, data collection in the main panel to complete the following features: Setting up access, set up sampling frequency, set up a manner that waveform, data collection in the main panel to complete the following Features: Acquisition of real-time signal and the signal on its own spectrum analysis, see lines, and other functions, and window panels dealing with the acquisition of real-time signal and the signal to increase processing windows (including windows Haiming, Hamming window, Buiakean smoothing windows and window, etc.).Filtering in handling panel includes the following features: the acquisition of real-time signal and the signal on its own filtering treatment (including single-step filtering, multi-step filtering method and tradit ional methods, etc.) The source files generated when the control panel to complete the set, you an have a function of the code of procedure. Specific methods for: to have completed c the panel as a response to the current state of the [Code] menu, select [Generate] in the [All Code], in the pop-up dialog function selected in the main panel and withdraw from the function , And the user interface will be able to produce documents relative to the framework of the code function. Add the code generated automatically step on the corresponding control is a function of the framework, to make certain controls to complete the function, we must add code to control the controls. One main () function is the entrance procedures, it is the function of initialization procedures, loading the user and display panels, such as to complete other functions required to add code. Following the code for data acquisition functions, data acquisition process by calling the callback function button SHOU external acquisition. Software development environment: virtual digital oscilloscope software design based on the use of C-language programming environment LabWindows / CVI. LabWindows / CVI support numerical type, Boolean, and the string of text, and other data types, but the biggest advantage is through dialog forms of interactive operations generate standard C code. In addition LabWindows / CVI provides a very rich debug tools, including single-step, breakpoints, variable view, monitor window, and so on, these features make the adjustment process has become more vulnerable. Have the function ? function with real-time display: Acquisition Acquisition signal to the input signal and real-time display in a PC terminal. ? digital filtering: IIR filter on the use of digital signal processing and real-time filtering, at the same time filter can be set up in the best approximation function type, filter type, order, from top to bottom cut-off frequency, and other parameters. ? latest wave show: to meet the transient waveform display, but can also be transient waveform to be saved. ? waveform storage: at any time after the original signal or signals to the LVM LabVIEW unique file format stored on the local hard drive, for future analysis or processing. One transient signal to the cut-off wave after BMP format images stored in local hard上供view and analysis of the future. ? significant wave back: to keep the memory of the LVM format waveform re-read the document and then displayed on a PC client. ? spectrum analysis: After the filter frequency signal respectively corresponding analysis and response analysis of the frequency and wave at the same time to show real-time manner and form. Basic principles the use of hardware acquisition card acquisition signals, using software provided by NI DAQmx READ acquisition signals, and then through Waveform Graphs to conduct real-time display. This has a basic oscilloscope, signal showed that after using Write To Measurement File waveform will be saved as LVM documents. This realization of the basic "store" function, but through Read To Measurement File can be read LVM, thus completing the "echo" feature. As the hardware and the acquisition of PC-card-based, so the limit of sampling oscilloscopes in the rate, bandwidth, resolution, and other parameters is limited. And procedures on the response time is dependent on the PC's configuration and procedures for the implementation of efficiency. The main function: DAQmx Read, Digital IIR Filter, Waveform Graphs, Write To Measurement File, Read To Measurement File, and other major function. Customizing the Waveform Graph The waveform graph indicator displays the two signals. To indicate which plot is the scaled signal and which is the simulated signal, you customize the plots. Complete the following steps to customize the appearance of an indicator on the front panel. 1. Move the cursor over the top of the plot legend on the waveform graph. Notice that while there are two plots on the graph, the plot legend displays only one plot. 2. When a double-headed arrow appears, shown in Figure 1-11, click and drag the border of the plot legend until the second plot name appears. Figure 1-11. Expanding a Plot Legend 3. Right-click the waveform graph and select Properties from the shortcut menu to display the Graph Properties dialog box. 4. On the Plots tab, select Sawtooth from the pull-down menu. Click the Line Color color box to display the color picker. Select a new line color. 5. Select Sawtooth (Scaled) from the pull-down menu. 6. Place a checkmark in the Don’t use waveform names for plot names checkbox. 7. In the Name text box, delete the current label and change the name of this plot to Scaled Sawtooth. 8. Click the OK button to apply the current configuration and close the Graph Properties dialog box. Notice how the plot color on the front panel changes. 9. Experiment with other properties of the graph by using the Graph Properties dialog box. For example, try disabling the autoscale feature located on the Scales tab. 10. Click the Cancel button to avoid applying the changes you made while experimenting. If you want to keep the changes you made, click the OK button. 11. Save and close this VI. Saving Data when Prompted by a User Complete the following steps to build a VI that logs data to a file when the user clicks a button on the front panel. 1. On the block diagram, double-click the Write LabVIEW Measurement File Express VI to access the Configure Write LabVIEW Measurement File dialog box. 2. Change the file name test.lvm to Selected Samples.lvm in the File name text box to save the data to a different file. 3. Close the Configure Write LabVIEW Measurement File dialog box. 4. Right-click the Signal input of the Write LabVIEW Measurement File Express VI. Select Insert Input/Output from the shortcut menu to insert the Comment input. 5. Right-click the Comment input of the Write LabVIEW Measurement File Express VI. Select Select Input/Output?Enable from the shortcut menu to insert the Enable input. In the previous exercise you learned to add inputs and outputs by expanding the Express VI using the down arrows. Notice that this method is a different way of displaying and selecting the inputs and outputs of an Express VI. The inputs and outputs of an Express VI appear in a predetermined order when you add new inputs and outputs. To select a specific input, you may need to add an input first, then change the input to the specific one you want to use. 6. Move the Write to File terminal to the left of the Write LabVIEW Measurement File Express VI. 7. Wire the Write to File terminal to the Enable input of the Write LabVIEW Measurement File Express VI. The block diagram should appear similar to Figure 2-6. Figure 2-6. Block Diagram for the Save Data VI 8. Display the front panel and run the VI. Click the Write to File button several times. 9. Click the STOP button on the front panel. 10. To view the data you saved, open the Selected Samples.lvm file with a spreadsheet or word processing application. Notice how the Selected Samples.lvm file differs from the test.lvm file. test.lvm recorded all the data generated by the Save Data VI, whereas Selected Samples.lvm only recorded the data when you pressed the Write to File button. 11. Save and close this VI. Or to talk about the need to improve the design of the place. The first is efficiency. Whether this design is from the original intention of the design or the result of design, are not fully take into account the efficiency of procedures and the efficiency of operation. Only a small number of functions and the realization of the need to optimize. This design were completed in less than one day of production, coupled with debugging time. Efficiency is not high enough reflected in the following areas. First, pipeline design process is running, the first concrete manifestation of the panel after the switch a few interface background did not stop running, but has been in operation, this will waste a lot CPU resources, only a simple function of the increase did not conduct an effective integration. Second, file storage efficiency is not high. LabVIEW provides a wide range of data storage file format, which is the most efficient binary form, followed by the text. The use of this design is unique to the LVM LabVIEW format, the benefits of doing so is called for, deficiency is not common, other software will not be able to read this document effective waveform information. With the Windows Notepad to open LVM documents found, in fact, LVM is a document essentially a text file, recording a wave of data related information, but the utilization rate is not high enough. Thirdly, it is part of the process of debugging tests left some function in the design of not deleted, only the former was hidden template processing, in fact CPU is still running in this part of the function of consumption of resources. Fourth is here to the six Waveform Graphs, just in front panel made a stack processing, it is a "screen" In fact, for certain procedures can significantly reduce the optimized use of Waveform Graphs. At the same time because in theory if not need to show that the public can be a "screen”. This was followed by the human-computer interface design. Ease of operation needs to be raised. In addition to the necessary self-button interface, the button should better. For example, switch interface automatically trigger procedures, and omit one of the switch button. In addition to the design of the interface graphics, there are too many forms, the ideal situation is designed to be hidden in control of the state model. Once again there is a regret. Can be designed as a dual-channel oscilloscope trace or more will be even more perfect. A high-end oscilloscope usually have two channels, and some have more spectrum for the channel. In fact, the increase in access is not difficult, but also far more than the traditional high-end oscilloscope the two channels. According to requirements of Title 32 of vertical resolution / div, oscilloscope, a total of eight grid, that is, divided into 256, the choice of eight A / D. Also because of the level of resolution of 20:00 / div, it corresponds to the third gear scan rate 0.2 s / div, 0.2ms/div, 20us/div the sampling rate is respectively 100 HZ, 100KHZ and 1 MHZ. As follows: a scanning speed of Xs / div, the level of demand for the resolution of 20:00 / div, so every point of sampling interval for X/20s, that is, the sampling frequency signal for the 20 / X HZ. Therefore, when the scanning speed of third gear requirements for 0.2 s / div, 0.2ms/div, 20us/div, corresponding to the third gear sampling frequency are 100 HZ, 100KHZ, 1MHZ. However, the 100 HZ to 100 KHZ the span too great, and not conducive to the middle band signals in the show, so we add a 1 KHZ and 10 KHZ Liangdang scanning speed. As the highest sampling rate to 1 MPS, so ordinary A / D to meet the requirements, so we selected TI's eight COMS ADC TLC5510. The chip single-5 V power supply, the conversion rate to a maximum 20 MPS, with a sampling of internal circuits and to maintain the benchmark resistance. The chip's biggest advantage is fast, simple control, programmable device to control. A / D circuit as follows: The A / D circuit of the dynamic range of input signal for a small 0.59 V ~ 2.59V. In order to be extended to the dynamic range of 0 ~ 10 V, to be in its previous level by adding the following adjustment circuit. In addition to the circuit five times the input signal attenuation, the input signal is still on the superposition of the 1.5 V DC. Control circuitry to do the programmable device, the main address cumulative unit, sampling speed option modules and programmable device and MCU interface unit. The address cumulative unit circuit as follows: CLK for the system clock, counting from the former first-chfa enter a negative pulse, D flip-flop on the counter and reset, then the clock counting. When the full terms, the circuit automatically cease to work and produce a low-INT signal to mark the end of counting. Onf signal to latch signal, when it was low, latch the current sampling. The choice of memory chips and real-time considerations: Option 1: a sampling data storage RAM, to put the first post-harvest methods of work. Circuit advantages of this method is simple, control simple, easy to implement. But only in the higher frequency when the input signal to a more stable output waveform, when the signal is very low, the output waveform update cycle is too long, the lack of real-time, and the output waveform data acquisition can not be carried out at the same time, some signal will be lost Information. Option 2: The two RAM, using a RAM storage of data collection, another film RAM output data, that is, two alternate RAM storage and output. The way to resolve some of the lost information signal, but the rate of mining must be consistent, otherwise the data will inevitably cause conflict. The method for low-frequency signals no meaning, no good solution to the problem of real-time and more complex circuits, the occupation of mouth line resources, wastage. Programme 3: I use one pair of RAM, while mining release. The method simple circuit, the better solution of the problem so the real-time use of the programme. As the highest sampling rate is 1 MPS, it demands the greatest memory access time should be less than 1 us. As the level of demand for the resolution of 20:00 / div, and a total of 10 analog oscilloscope grid, that is, every time scanning should have 200 points, Therefore, storage of only 200 units. When the input signal an acquisition, the assumption that the largest full screen display a cycle of the signal, the storage period of 10 signals on the topic has been over-meet the requirements, the storage capacity as 2 K we choose the dual-port RAM is IDT7132, the chip There are two symmetrical signal that each port has its own address lines, data lines and the Line of Control. The access time for the 25 ns ~ 35ns, storage capacity of 2 K, in the non-elected automatically in low-status, asynchronous operation, three-state input and output, and TTL-level compatible. Waveform display circuit: a waveform display X-Y manner and external trigger mode. However, in order to show the oscilloscope characters must choose X-Y approach. 1) Analysis of the data output rate: As the maximum speed of data acquisition for 1 MHZ, so data playback system scan rate should be more than 1 MHZ, can display real-time data update process. According to the experiment, we selected output frequency to 2 MHZ. In the output frequency, the real-time system better, and waveform stability, not distortion. We choose the DA is DAC0800, its output current set-up time for the 100 ns, that is, 10 MHZ, the speed of data output to meet demand. Output data from the address by address accumulator, we address the accumulator after class to join the select level data, by scanning signals into digital data pulse switch channels, you can achieve after the latch or a single wave triggered after the show Mobile level. Sawtooth formation circuit: It was found that the programmable device EPM7128SLC84-15 counting the internal structures of the circuit is very easy to have a burr so that the output sawtooth instability, thus we have a choice of hardware circuit count sawtooth. Sawtooth clock output from the circuit to provide data to ensure that the scanning signal and data signals simultaneously. Sawtooth dollars will be upon expiry of the binary pulses output after a delay Larger, gave the Z-axis analog oscilloscope, blanking flyback line. Trigger circuit: trigger level by the microcontroller through the D / A (MAX508) output, by comparison with the input signal is compared to be trigger signal. The trigger signals to a microcontroller interrupt, the MCU after launch EPM7128 start collecting. Selection of the circuit here is relatively high gain, low noise, low drift Yun-OP37 posed by open-loop. Its output by two diode limiter to be the standard TTL signal. Two-trace Oscillographic circuit: theoretically strict trace oscilloscope to double two-way signal sampling at the same time, then need two high-speed A / D, and its front-end circuit. But ordinary analog oscilloscope resolution is generally not high, thus has no significance to strictly require the two signals at the same time. Therefore, we used all the way acquisition circuit of the two alternate input signal sampling, data were collected will be stored in the memory of the odd-even address, respectively Oscillographic, the same can be done with high precision dual-trace Oscillographic, and to make the system Price increase. Minimum system circuit: the system to AT89C52 as the core. 20 keys from the keyboard composed by MM74C923 completed its scan. Display System is the DCM-162A, it is character LCD, there are two lines of 16, from 8-bit characters in each line of five, because of its resolution is not high, difficult to display Chinese characters, so we use All English interface. In addition, the system also has 32 K of RAM (62256) and a 82 C55 port expansion as a backup. Part of the power system for the +5 V, +12 V and -12 V power supply three ways. Frequency Measurement modules: the use of SCM counter to measure the signal. Because the trigger pulse with the same input signal frequency, so just to trigger a pulse frequency can be measured. When the frequency of less than 5 Khz, the use of the method of measurement weeks, the measured signal to the gate for a period of time, the MCU to a machine cycle (1 us) for the benchmark time, that is, in its count cycle. When the input signal in the 5 K-50K when measured by the frequency approach to the measured signal for the time benchmarks for the regular 1 S gate time, a time-count, that is, in frequency. Characters display module. The level of input in the X-axis scanning signal, in Y-axis input field scanning signal, the Z-axis input signal brightness can be formed on the characters in the oscilloscope. The field scanning signals generated by the EPM7128 internal count. Z-axis data exist in the external ROM. Peak peak measurements: general AD (MAX197) on the importation of high-speed acquisition circuit to signal a longer time of sampling, get input signal to the maximum and minimum, and then their poor Value prior to passage by the decay times, you can get the input signal peaks peak. AUTO-SCALE function: This feature automatically adjust to achieve the level of sensitivity and vertical sensitivity, so that waveform better be displayed. First, the system through the regular AD (MAX197) read as an input signal level trigger level so that the system is stable trigger. Then, call frequency measurement function, measured the frequency of input signal, because the level of sensitivity we will be divided into 20 us / div, 0.2ms/div, 2ms/div, 20ms/div, 0.2s/div five stalls, in order to ensure that at least on the oscilloscope That a cycle of signal, so when the measured signal frequency f> 5khz, with 20 us / div stall when the 500 hz， This system of measurement, the function and meet the targets were subject requirements. Completion of the functions are as follows: the input signal can be a single trigger, the trigger after the show that stability can not change with the input signal changes, the signal of a sampling of up to 2,048 sample points in a row could trigger mode of input signal sampling and real-time , And no significant wave distortion, the input signal is the exchange can also be a DC; activated the latch key to lock the current wave of storage and can wave to move through the level of observation, the software can be set up or choose a channel signal 2-channel signal or two-mode disappeared when the input signal to trigger the rising edge of peacetime to generate a trigger, the trigger level stability adjustable; sampling of the signal output at the level of scanning speed is 0.2 s / div, 20ms/div, 2ms / div, 0.2ms/div, 20us/div five stalls, there are vertical sensitivity of 0.01 v / div, 0.05v/div, 0.1v/div and 1 v / div total Sidang; can be measured on the input signal frequency, measured weeks, and measure - Peak, according to the input signal can be adaptive, that is, auto-scale function. The actual measurement results are as follows: (1) vertical sensitivity test: When the oscilloscope vertical sensitivity set at 0.5 v / div, if the system of vertical sensitivity set at 0.1 v / div, the input signal peak-to 500 mv, displayed on the oscilloscope 5 Georgia; If the system of vertical sensitivity set at 1 v / div, the input signal for the peak-5 v, 4.9 grid displayed on the oscilloscope. Two indicators of measurement data are in line with demand. (2) the level of scanning speed test: When the input signal frequency set at 1 hz, scanning speed set at the level of 0.2 s / div, displayed on the oscilloscope 5 grid; input signal frequency set at 10 khz, the level of the scanning speed in the 20 us / div , The oscilloscope show the 5 grid. Two measurements are also indicators of demand. (3) input noise measurements: the input termination, in the oscilloscope measured the level of scanning lines the width of about 3 mv.. So virtual instrument technology are computers, measuring instruments, the apid development of software technology and integration and孕育out a new r technology. Virtual instrument technology is the core of the powerful use of computer resources so that the necessary hardware to achieve the technology and software to minimize system cost, enhance system functionality and flexibility, compared with the electronic devices have great advantages. The virtual digital oscilloscope on the design and implementation of the principle, the use of VB programming, data collection, such as through the use of hardware, achieving a double-trace oscilloscope features, dual-channel display, measuring the voltage input signal, the frequency of cycles and storage, and other signals. The virtual computer equipment is the intelligent electronic measuring instruments. Virtual instrument through dedicated hardware and software modules constitute a good human-computer interface, users can customize the testing capabilities and to enable the measurement object diversification. Virtual machines external interface through the data acquisition card after the signal sent to computer data acquisition, complex testing, data analysis and results are completed entirely by computer software. A good performance of the virtual instrument can be achieved not only the most traditional instrument measurements, in many ways than the traditional instruments are incomparable advantages, such as the use of flexible, testing, feature-rich, low prices, such as the use of a machine, which makes Virtual machines become the future development of electronic measuring instruments in the direction even broader. The final design of a graphical programming language LabVIEW and object-oriented programming techniques, in order to increase its spectrum analysis can not only observe that wave, also can enter data for analysis. Collection of data entered the store, measuring results and waveforms can directly input and output (or Dupan archiving). Played a powerful computer data-processing capabilities and software design flexibility. 虚拟数字存储示波器 虚拟数字存储式示波器的结构与组成:虚拟数字示波器由一块PXI总线的多功能数据采集卡和相应的软件组成。将它们安装在一台运行Windows的PC上，即构成一个功能强大的可存储数字示波器。 数据采集卡 中所采用的是NI公司生产的多功能数据采集卡PXI-6670E，其主要功能如下: 64路单端/32路差分模拟输入;12位精度;1.25MSPS采样速度;1.25MSPS磁盘写入速度;?0.05,?10V输入范围;两路12位模拟输出;8条数字I/O线;两路24位计数器/定时器。 仪器功能: 虚拟数字示波器具有实时数据采集、频谱分析、加窗处理和滤波等功能。在虚拟数字示波器主面板上有数据采集、频谱分析、加窗处理、滤波功能等功能键，按相应的功能键就可进入相应的子面板。 软件的设计与实现: 虚拟数字示波器软件设计采用了基于C语言的编程环境LabWindows/CVI。LabWindows/CVI支持数值型、布尔型、文本型和串等数据类型，而且最大优点是能够通过对话框形式的交互式操作生成标准C程序代码。另外LabWindows/CVI提供了非常丰富的调试工具,包括单步执行、断点、变量查看、监视窗口等，这些功能使程序的调试变 得更为容易。 主要功能模块: 虚拟数字示波器主要由软件控制完成信号的采集和显示处理，在数据采集面板中主要完成以下功能:设置通道、设置采样频率、设置产生方式、显示波形等，在数据采集面板中主要完成以下功能:对实时采集的信号和自行产生的信号进行频谱分析，查看谱线等功能，加窗处理面板对实时采集的信号和自行产生的信号加窗处理(包括海明窗、汉明窗、平滑窗和布拉克曼窗等)。在滤波处理面板中包括以下功能:对实时采集的信号和自行产生的信号进行滤波处理(包括单步滤波法、多步滤波法和传统方法等). 源程序文件的生成: 当完成面板各个控件的设置后，就可以产生程序的代码函数了。具体方法为:把已完成的面板定为当前响应状态，在[Code]菜单中，选中[Generate]中的[All Code]，在弹出的对话框中选定函数主面板和退出函数，就能产生与用户接口文件相对应的框架代码函数。 添加程序代码: 上一步自动生成的是控件对应的函数的框架，要使控件完成一定的功能，必须添加程序代码来控制控件。其中main()函数是程序的入口，它的功能是初始化程序，装载用户面板并显示，如要完成其他功能须添加代码。以下这段代码实现数据采集功能，程序通过调用数据采集按钮的回调函数SHOU进行外部采集。 软件开发环境:虚拟数字示波器软件设计采用了基于C语言的编程环境LabWindows/CVI。LabWindows/CVI支持数值型、布尔型、文本型和串等数据类型，而且最大优点是能够通过 对话框形式的交互式操作生成标准C程序代码。另外LabWindows/CVI提供了非常丰富的调试工具,包括单步执行、断点、变量查看、监视窗口等，这些功能使程序的调试变 得更为容易。 另外虚拟示波器相比传统示波器具有价格低廉、功能丰富、可编程性以及显示直观等众多优势。本设计不仅仅具有示波器基本功能，更依据LabVIEW语言的特点丰富了数字滤波、信号保存以及回显等功能。不仅具有了价格低廉、界面美观等特点，而且具有传统示波器中比较高端的存储、回显以及数字滤波等功能，更可以根据需要随时灵活修改程序，增加功能以满足更个性化的要求。 具备功能: ?实时显示:通过采集卡采集信号并能对输入信号实时显示在PC机终端上。 ?数字滤波:采用数字IIR滤波器对信号进行滤波处理并实时显示，同时可以任意设置滤波器的最佳逼近函数类型、滤波器类型、阶次、上下截止频率等参数。 ?截波显示:即可满足波形的瞬态显示，同时也可以将瞬态波形进行保存。 ?波形存储:可随时将原始信号或处理后信号以LabVIEW特有的LVM文件格式存储在本地硬盘上，便于日后分析或处理。其中瞬态信号在截波后以BMP图片格式存储在本地硬盘上供日后查看以及分析。 ?波形回显:随时将存储的LVM格式波形文件重新读取然后显示在PC机端。 ?频谱分析:对滤波后信号分别进行幅频相应分析以及相频响应分析并同时采取波形与表格方式实时显示. 基本原理: 硬件上利用采集卡采集信号，软件上利用NI提供的DAQmx READ采集信号，然后通过Waveform Graphs进行实时显示。这就实现了一个最基本的示波器，信号显示后又利用Write To Measurement File将波形保存为LVM文件。这就实现了基本的“存储”功能，反之通过Read To Measurement File可以将LVM读取显示，从而完成“回显”功能。 由于在硬件上是以PC机以及采集卡为基础的，所以本示波器在采样极限速率，带宽，分辨力等参数上受到限制。而程序响应时间上则依赖于PC的配置以及程序的执行效率 主要的函数: DAQmx Read、Digital IIR Filter、Waveform Graphs、Write To Measurement File、 Read To Measurement File等主要函数 定制波形图: 波形图显示了两个信号。为了区分缩放信号的曲线和模拟信号的曲线， 您需要定制曲线绘制。完成下面的步骤可以定制在前面板内显示件的外观。 1. 移动光标至波形图中的曲线图例顶部。 注意在图表中有两个曲线，在曲线图例中却只显示了一条曲线。 2. 当双向箭头出现时，如图1-11，点击并拖曳曲线图例的边框直到出 现第二条曲线名字。 3. 右击波形图，从快捷菜单中单击Properties，显示出Graph Properties 对话框。 4. 在Plots 标签内，从下拉菜单中选择Sawtooth。点击Line Color 调色盒显示出颜色拾取工具，并选择一个新的线条颜色。 5. 从下拉菜单中选择Sawtooth(Scaled)。 6. 选中Don’t use waveform names for plot names 复选框。 7. 在Name 文本框内，删除现在的标记，改变该条曲线的名字为 Scaled Sawtooth。 8. 点击OK 按钮，应用当前的配置，并关闭Graph Properties 对话 框。 注意: 在前面板内的曲线颜色发生了改变。 9. 利用Graph Properties 对话框试验图表的其它属性。例如，在 Scales 标签内，禁用自动缩放功能。 10. 当您试验时，点击Cancel 按钮可以使您改变的设置无效。如果应 用您改变的设置，则点击OK 按钮。 11. 保存并关闭该VI 程序。 用户控制下的存储数据: 完成下面的步骤，来创建一个VI 程序，当用户点击前面板的一个按钮时， 把数据存入一个文件。 1. 在程序框图上，双击Write LabVIEW Measurement File Express VI 来打开Configure Write LabVIEW Measurement File 对话框。 2. 把File name 文本框中的文件名test.lvm 改变为Selected Samples.lvm，使数据存入一个不同的文件。 3. 关闭Configure Write LabVIEW Measurement File 对话框。 4. 右击Write LabVIEW Measurement File Express VI 的Signal 输入， 从快捷菜单中单击Insert Input/Output，来插入Comment 输入。 5. 右击Write LabVIEW Measurement File Express VI 的Comment 输入，从快捷菜单中单击Select Input/Output>>Enable，来插入 Enable 输入。 当您添加了新的输入输出时，Express VI 的输入输出按照预定义的 顺序显示。为了选择一个特定的输入，您必须先添加一个输入，然后 改变该输入为您所想用的那个。 6. 移动Write to File 连线终端到Write LabVIEW Measurement File Express VI 的左边。 7. 将Write to File 控件终端连接到Write LabVIEW Measurement File Express VI 的Enable 输入端。 程序框图如图2-6 所示。 图2-6 Save Data VI 的程序框图 8. 显示前面板，运行VI。点击Write to File 按钮几次。 9. 点击前面板上的STOP 按钮。 10. 要查看保存的数据，用电子表格或word 处理软件打开Selected Samples.lvm 文件。 注意，Selected Samples.lvm 不同于test.lvm 文件。Test.lvm 文件 记录了Save Data VI 产生的所有数据，而Selected Samples.lvm 仅 仅记录了当您按Write to File 键时的数据。 11. 保存，关闭此VI 程序。 首先是效率的提高。本设计无论是从设计的初衷还是设计的结果来看，都没有充分考虑到程序的效率以及操作的效率来。仅为功能的实现以及少量必要的优化。本设计仅用了不到一天的时间制作，还加上调试时间。效率不够高体现在以下几个方面。 一是程序是流水线式设计运行，具体体现在前面板的几个界面切换后后台并没有停止运行，而是一直在运行，这样会浪费不少CPU资源，功能只是简单的增加而没有进行有效的整合。 二是文件存储的效率不高。LabVIEW提供多种文件格式的存储数据，其中效率最高的是二进制文件形式，其次是文本形式。而本设计采用的是LabVIEW所特有的LVM格式，这样做的好处是调用方便，缺点是不具有通用性，其他软件将无法读取这种文件的有效波形信息。用Windows的记事本打开LVM文件后发现，其实LVM文件本质也是一种文本文件，记录了波 形数据的相关信息，但利用率不够高。 三是有部分调试测试过程中留下的一些函数在本设计中没有删去，只是在前模板作了隐藏处理，实际上CPU依然在为运行这部分函数消耗资源。 四是这里用了六个Waveform Graphs，只是在前面板上作了叠加处理，看起来是一个“屏幕”，实际上程序作一定的优化后可以大量减少Waveform Graphs的使用。因为理论上只要不是同时显示的需要就可以公用一个“屏幕”。 其次是人机界面的设计。操作的方便性有待提高。自我感觉界面除了必要的按钮外，按钮应该越少越好。例如界面切换后自动触发程序，而省去一个个的开关按钮。本设计的界面除了图形显示外，还有过多的表格显示，理想的情况是设计成可控制显隐状态的模式。 再次是有一个遗憾。能设计成一个双踪或多通道的示波器将更加完美。一台高端的示波器通常具备两个通道，而一些频谱仪则有更多的通道。实际上在通道的增加并不困难，而且可以远远地超过传统高端示波器的两个通道。 根据题目要求垂直分辨率为32级/div,示波器上共8格，即要分为256级，因此可选用8位A,D。又由于水平分辨率为20点/div,所以对应于三档扫描速度0.2s/div,0.2ms/div,20us/div的采样速度应分别是100HZ，100KHZ和1MHZ。分析如下: 设扫描速度为,s/div,要求水平分辨率为20点,div,所以每点的取样时间间隔为X/20s,即取样信号的频率为20/X HZ。因此，当要求三档扫描速度分别为0.2s/div,0.2ms/div,20us/div时，相应的三档采样频率应分别是100HZ，100KHZ，1MHZ。但是，从100HZ到100KHZ的跨度太大,不利于中间频段信号的显示，因此我们又多加了1KHZ和10KHZ两档扫描速度。由于最高采样速率达到1MPS，所以普通的,,,难以满足要求，因此我们选用了,，公司的8位COMS ADC TLC5510。该芯片用单5V供电，转换速率最高可达到20MPS，内部带有采样保持电路和基准电阻。该芯片的最大优点就是速度快，控制简单，适用于可编程器件控制。,,,电路如下: 该,,,电路的输入信号的动态范围很小为0.59V~2.59V。为了将动态范围扩展至0~10V，需在其前级加入如下调整电路。该电路除了对输入信号进行5倍衰减外，还在输入信号上迭加1.5V的直流。 控制电路做在可编程器件里，主要有地址累加单元，采样速度选择单元和可编程器件与单片机接口单元。 其中，地址累加单元电路如下: CLK为系统时钟，计数前首先由chfa端输入一个负脉冲信号，对计数器和D触发器复位，而后对时钟脉冲计数。当计满时，该电路自动停止工作，并在INT端产生一个低电平信号，标志计数结束。Onf信号为锁存信号，当其为低电平时，锁存当前采样。 存储芯片的选择与实时性的考虑: 方案一:采用一片RAM存储采样数据，以先采后放的方法工作。该方法优点是电路简单，控制简单，易于实现。但其只在输入信号频率较高时能输出较稳定的波形，当信号频率很低时，输出波形更新周期过长，缺乏实时性，并且在输出波形的同时无法进行数据采集，将丢失信号部分信息。 方案二:采用两片RAM,用一片RAM存储采集数据，另一片RAM输出数据,即两片RAM交替进行存储与输出。该方法解决了丢失信号部分信息的问题，但是采放的速率必须一致，否则必然引起数据冲突。对于低频信号该方法无任何意义，没能很好的解决实时性问题，并且电路较复杂，占用口线资源多，造成浪费。 方案三:采用一片双口RAM ,边采边放。该方法电路简单，较好的解决了实时性问题所以采用该方案。由于最高采样速度是1MPS，所以要求存储器的最大存取时间应小于,us。由于要求水平分辨率为20点/div，而模拟示波器上共有10格，即每一次扫描应有200个点，所以存储量仅需200个单元。当对输入信号一次采集时，假设最大满屏显示一个周期的信号，则存储10个周期的信号就已经超额满足题目的要求，因此存储量选为2K我们选择的双口RAM是IDT7132，该芯片有两组对称的信号线，即每个端口都有独立的地址线,数据线和控制线。它的存取时间为25ns~35ns ，存储量为,,，在非选通时自动处于低耗状态，可异步操作，输入和输出三态，与TTL电平兼容。 波形显示电路: 波形显示方式有,,,方式及外部触发方式。但是为了在示波器上显示字符就必须选用,,,方式。 数据输出速率的分析: 由于数据采集的最高速度为1MHZ，因此数据回放系统的扫描速率应大于1MHZ，才能实时的显示数据更新的过程。根据实验比较，我们选定输出频率为2MHZ。在该输出频率下，系统的实时性较好，而且波形稳定，不失真。我们选用的DA是DAC0800，它的输出电流建立时间为100ns,即10MHZ，满足数据输出的速度要求。 输出数据的地址由地址累加器得到，我们在地址累加器的后级加入了一级数据选择器，通过扫描信号的进位脉冲切换数据通道，即可实现锁存后或单次触发后显示波形的水平移动。 锯齿波形成电路: 根据实验发现，在可编程器件EPM7128SLC84-15的内部搭建的计数电路很容易产生毛刺，使输出锯齿波不稳定，因而我们选用硬件电路计数产生锯齿波。锯齿波的时钟由数据输出电路提供，以保证扫描信号与数据信号同步。将锯齿波计满后输出的进位脉冲经过一定的延时放大后，送给模拟示波器的,轴，以消隐回扫线。 触发电路: 触发电平由单片机通过D/A(MAX508)输出，通过比较器与输入信号相比较，从而得到触发信号。该触发信号使单片机产生中断，经单片机处理后启动EMP 7128开始采集。 这里选用的比较电路是由高增益，低噪声，低漂移运放OP37开环构成的。其输出用两个二极管限幅，以得到标准的TTL信号。 双踪示波电路: 理论上严格的双踪示波器应对两路信号同时采样，那麽就需要两个高速A/D，及其前端电路。但是普通模拟示波器分辨率一般不高，因而就没有任何意义去要求两路信号严格的同时。因此我们采用一路采集电路对两路输入信号交替采样，将采集数据分别存储于原存储器的奇偶地址内，再分别示波，同样可以以较高的精度作到双踪示波，并且使系统的性价比提高。 最小系统电路: 本系统以AT89C52为核心。键盘由20个按键组成，对其扫描由MM74C923完成。系统的显示器用的是DCM-162A，它是字符型LCD，共有两行十六列，每个字符位由8行5列组成，由于其分辨率不高，难以进行汉字显示，因此我们采用全英文界面。此外该系统还带有32K的RAM(62256)和一片82C55作为端口扩展备用。系统的电源部分为+5V，+12V及-12V三种供电方式。 测频模块: 利用单片机的计数器对信号进行测量。因为触发脉冲与输入信号频率相同，所以只需对触发脉冲进行测频即可。当频率低于5Khz时，利用测周的方法，以被测信号的一个周期为闸门时间，以单片机的一个机器周期(1us)为时间基准，对其计数即得周期. 当输入信号在5K-50K时用测频的方法，以被测信号为时间基准，定时1S为闸门时间，对时基计数，即得频率. 字符显示模块: 在,轴输入水平扫描信号，在,轴输入场扫描信号，在,轴输入亮度信号即可在示波器上形成字符。其中，场扫描信号由EPM7128内部计数产生。,轴的数据存在外部ROM中. 峰峰值测量功能: 用普通AD(MAX197)对输入到高速采集电路的信号进行较长时间采样，从中得到输入信号的最大值和最小值，然后将它们的差值乘以前向通道的衰减倍数后，即可得到输入信号的峰峰值. AUTO-SCALE 功能: 此功能实现系统自动调节水平灵敏度和垂直灵敏度，使波形更好的被显示。首先，系统通过普通AD(MAX197)读取输入信号电平作为触发电平，使系统稳定触发。然后，调用测频功能，测得输入信号的频率，由于我们将水平灵敏度分为 20us/div,0.2ms/div,2ms/div,20ms/div,0.2s/div五档，为保证示波器上至少显示一个周期的信号，所以当被测信号频率f>5khz时用20us/div档;当500hz