技术图纸的模拟／数字扫描技术

技术图纸的模拟／数字扫描技术美国最近推出了一种名为“ＳａｎＶａｎｔａｇｒ“（扫描优势）的技术图纸模拟／数字扫描技术。该技术是一种革命性的新技术，它把照相复制和数字扫描这两种技术结合到了一起。由于该技术是以照相技术为基础的，故其效果远优于扫描编辑处理技...     

基于IEEE1149．1标准的边界扫描测试技术与方法的研究

边界扫描测试技术是目前一种主流的可测性设计技术,它以特有的结构和检测方法克服了复杂数字电路板测试的技术障碍,能大大提高数字电路的可测试性。本文在深人研究IEEE1149．1边界扫描标准的基础上,根据边界扫描标准定义的测试结构对数字系统的测试方法进行研究,设计出符合IEEE1149．1标准的边界扫描测试系统。主要研究内容如下：详细分析IEEE1149．1标准中定义的测试结构;基于IEEE1149．1标准,提出数字系统边界扫描控制器的设计方案并实现其硬件设计,包括边界扫描控制模块等,并编写上位机软件;最后对数字系统边界扫描测试中的测试方法进行研究。该系统具有极大的应用前景,可以广泛应用于大规模数字集成电路的测试。     

传感器智能化变换器设计与应用

文章介绍了一种智能化变换器的设计以及在称重／N力领域中的应用。它集多通道、运放、A／D、CPU、I／O为一体．输出为标准的数字量信号，外壳采用全不锈钢设计，密封性好，抗干扰能力强，精度高，功能多，实现了多个传感器的远距离传输，可直接与计算机通讯。经实验，该变换器在量程范围内均达到0．01％的准确度。     

数字多用表在测量低频交流电压中的误差分析

本文对基于数字采样技术的真有效值变换器数字多用表在测量低频交流电压时的误差进行了分析 ,并给出了理论计算值及实际测量结果。     

数字化技术在转速变换器计量校准中的应用

转速变换器是一种将频率量转换为电压量的二次装置，目前采用人工手动校准，效率低下且操作烦琐，易发生人为失误。本文在校准过程中引入数字化技术，实现了数据自动处理、报告一键生成等功能，同时建立专用校准数据库，采用数据挖掘等技术进行深度分析，为变换器的设计提供一定的参考。     

YEW2885-20型功率变换器的校准与调整

2885—20型功率变换器(日本横河生产)是一种高精度、宽范围的功率/直流电压变换器,当配用直流数字电压表时,它就构成了高精度的交流数字功率表,因此它广泛用于省市计量部门、电力中心试验所及电能表生产厂作电功率/电能标准的计量仪器。一、工作原理:仪器的工作原理如图1所示,输入的交流电压和电流信号经两个电流互感器(CT)转换     

采用数字同步技术的轴类零件尺寸光电检测

根据线阵CCD对二维图像进行扫描检测的特点,提出一种基于数字同步技术的轴类零件尺寸检测方法。它用数字方法保证扫描位移量(或者位移速度)与CCD行扫描次数(或者行扫描速度)严格对应,CCD的行扫描由扫描位移量控制,有效消除了被测物体运动速度变化对检测分辨力和精度的影响,提高了检测精度;采用数字同步技术,使检测在扫描位移的加速、恒速和减速过程中均能进行,提高了检测速度;采用图像边缘自动跟踪方法,自动获取边缘参数,实现被测物体的二维多尺寸自动定位检测。检测实验表明,该方法的检测误差≤0.02mm;当被测物体轴向尺寸为100mm时,检测时间<5s。     

与《一种新型胶片划痕修复液的研究》一文的作者商榷

本文对《一种新型胶片划痕修复液的研究》(发表于本刊2015年第8期)一文所阐述的电影胶片划痕修复液研制的方法设计、指标设定、试验依据等提出了改进建议,并对掩盖电影胶片划痕的三种方法 (湿法复印、数字扫描和附加修复膜)进行了比较。本文认为,用湿法数字扫描来消除胶片表面划痕对电影画面的影响是应用前景最广的技术,也是性价比最好的技术和相对最符合电影保护和保存的最可靠的技术。     

软开关变换器的设计与仿真研究

针对开关电源开关损耗和电磁辐射的问题，建立了一种采用软开关技术的零电压开关（ZVS）PWM变换器的电路，利用PSpice软件对这种变换器进行仿真研究，分析其暂态和稳态时的性能。仿真表明，合理选择器件参数，当软开关变换器电路中L1=0.3mH，L2=3μH，C1=500p时，开关损耗小，造成的电磁干扰小。仿真发现暂态时开关器件承受了较高的电压应力，实际应用时应考虑开关器件安全性。     

扫描底片斑痕的处理

数字图像与传统意义的照片属性相当，同属照片范畴。如果把传统的底片照片通过电子扫描仪扫描生成数字照片，不但克服了传统照片载体耐久性差的缺点，还可以对图像进行数字处理，直接发挥数字技术的优势。     

个人微机仪器式数字示波器

本文介绍一种个人微机仪器（ＰＣＩ）式数字示波器的硬件、软件原理。该仪器采用高速并行Ａ／Ｄ变换器进行数据采集，其数字化率为２０ＭＳ／ｓ，分辨率为８ｂｉｔ。微机控制输入信号的放大和采集，并把采集到的信号实时地显示在微机的监视器上。该仪器不但具有一般双通道数字示波器的功能，而且在不增加硬件投人的情况下，只要编写相应的应用软件就可以对两路输人波形进行分析、运算。适用于电子学研究、生物学研究，以及电子、磁性材料测试和医疗监视等各个领域。     

Acousto-optical deflection-based laser beam scanning for fluorescence detection on multichannel electrophoretic microchips

Laser beam scanning driven by an acousto-optical deflector (AOD) is presented for multimicrochannel laser-induced fluorescence (LIF) detection during microchip-based electrophoresis. While fast laser beam scanning for LIF detection on capillary or microchannel arrays can been achieved with galvanometric scanning or a translating stage, it can also be accomplished by using acoustic waves to deflect the laser beam in a manner that is dependent on the acoustic frequency. AOD scanning differs from other approaches in that no moving parts are required, and the scan frequency is faster than conventional approaches. Using a digital/analog (D/A) converter to provide addressing voltages to a voltage/frequency converter, rapidly changing the frequency input to the AOD allows the laser beam to be addressed accurately on a microchip. With the ability to change the frequency on the nanosecond time scale, scanning rates as high as 30 Hz for Windows-based LabView programming are possible, with much faster scan rates achievable if a microprocessor-embedded system is utilized. In addition to spatial control, temporal control is easily attainable via raster scanning or random addressing, allowing for the scanning process to be self-aligning. Since the D/A output voltages drive the scanning of the laser beam over all channels, the software can define addressing voltages corresponding to the microchannel centers and, subsequently, fluorescence data can be collected from only those locations. This method allows for flexible, high-speed, self-align scanning for fluorescence detection in capillary or microchip electrophoresis and has the potential to be applied to a number of applications.     

A New Low Cost Linear Resolver Converter

A new low cost converter topology is proposed for sinusoidal position encoders. The converter enables determination of the angle from the sine and cosine signals of the encoder. When used with resolvers, the implementation of the present scheme takes advantage of the available excitation signal used to operate the device. This trigonometric reference signal is optimally used to generate an analogue signal equivalent to a digital look-up table (LUT). This enables determination of the mechanical angle without using LUT, A/D, and D/A converters. The scheme is optimized in order to achieve highest possible precision. Beside simplicity of its implementation, the proposed converter offers the advantage of robustness to amplitude fluctuation of the transducer excitation signal. The converter was implemented using ordinary low-cost analog components. The theory of operation, computer simulation, and experimental results are given.      

New ADC with piecewise linear characteristic: casestudy-implementation of a smart humidity sensor

In this paper, the architecture of a new analog-to-digital converter (ADC) with a piecewise linear characteristic (PLADC) is proposed. In this device, some discrete points of the characteristic can be modified to fit a requested profile. This converter facility can be utilized to gain remarkable advantages in a wide variety of applications, such as the implementation of a sensor linearization technique. In the paper the internal architecture of a two-stage 11-b flash PLADC prototype is briefly described. A representative demonstrative application, namely, the implementation of a linear digital humidity sensor, is discussed showing the effectiveness and usefulness of this device. The problem of the characterization of this converter is also discussed, reporting some remarks about the implemented solutions     

测量低信噪比电压的数字相敏解调算法及性能分析

本文研究了低信噪比正弦电压幅值及相位测量用的数字相敏解调（ＤＰＳＤ）算法，给出了ＤＰＳＤ算法的主要参数（数据长度、取样频率、Ａ／Ｄ转换器位数）与低信噪比电压测量的性能指标（测量精度、频率分辨力、动态储备及最小可测电压）之间的关系。对纳伏电压的实际测量表明，理论分析与测量结果是一致的。本文研究结果可以用于数字式相敏解调程序的设计及应用     

High-frequency ultrasound annular array imaging. Part II: digital beamformer design and imaging

This is the second part of a two-paper series reporting a recent effort in the development of a high-frequency annular array ultrasound imaging system. In this paper an imaging system composed of a six-element, 43 MHz annular array transducer, a six-channel analog front-end, a field programmable gate array (FPGA)-based beamformer, and a digital signal processor (DSP) microprocessor-based scan converter will be described. A computer is used as the interface for image display. The beamformer that applies delays to the echoes for each channel is implemented with the strategy of combining the coarse and fine delays. The coarse delays that are integer multiples of the clock periods are achieved by using a first-in-first-out (FIFO) structure, and the fine delays are obtained with a fractional delay (FD) filter. Using this principle, dynamic receiving focusing is achieved. The image from a wire phantom obtained with the imaging system was compared to that from a prototype ultrasonic backscatter microscope with a 45 MHz single-element transducer. The improved lateral resolution and depth of field from the wire phantom image were observed. Images from an excised rabbit eye sample also were obtained, and fine anatomical structures were discerned.     

简易光纤陀螺测试系统的设计与实现

光纤陀螺是20世纪70年代发展起来的一种新型惯性仪器，由于具有精度高、抗干扰能力强、预热时间短等一系列优点，在各个领域得到了广泛的应用。而要保证光纤陀螺的测试精度，一套高精度的测试系统是必不可少的。论文针对模拟光纤陀螺进行测试系统设计，以往采用较多的测试方法为：首先对信号进行A/D转换，再利用计算机进行数字信号采集；但由于AD转换存在精度低及连续性差等缺点，大大限制了测试系统的精度。基于这一方面考虑，论文中设计了一种简易的高精度光纤陀螺多路测试系统，直接对输出的模拟信号进行采集，再利用采集到的电压信号进行解算，得到角速度值。在组建完整套测试系统后，对设计的测试系统进行了试验验证及精度标定，试验结果表明，该测试系统具有较高的精度，完全可以满足中低精度模拟光纤陀螺的测试要求。     

Digital Ventilated Psychrometer

A digital ventilated psychrometer for direct reading of the relative humidity (RH) from the digital indicator by means of two identical type thermistors is described. The method is based on the temperature to linear voltage converter, the calculator of the dry and wet bulb temperature ratio, the converter from the ratio to the voltage proportional to RH, and the analog to digital (A/D) converter. The experimental result by the digital ventilated psychrometer shows that the apparatus makes the direct indication of RH possible. The accuracy of the apparatus is estimated to contain an RH error of less than 2 percent and it is almost the same as that of the Assmann psychrometer. The principal advantage of the apparatus is the direct indication of RH and the capability to use the data directly for the input of the digital data processor.     

Digital-to-analog (D/A) converters with nonuniformly sampledsignals

In this paper, we investigate the problem of the D/A converter with nonuniformly sampled input data. The input digital data were obtained by sampling the intended analog waveform at nonuniform time intervals, and we look into the question: “Given that the timing offset of each data sample is known, would it be beneficial, in terms of the output signal-to-noise ratio, to use this offset to adjust the playback timing of the D/A converter?” We examine two different timing strategies. The first approach simply plays out the signal at a uniform rate, while the second one uses the known timing offset to adjust the D/A converter playback timing accordingly. The closed-form expressions of the spectrum of the D/A converter output signals are derived. From these expressions, we find that the spectrum structure, for the case where the timing offsets are compensated, is the infinite sum of the weighted shift to the baseband spectrum. For the uniform playout approach, the spectrum structure is much more complicated where each shifted spectrum is modified by a different weighting function of the frequency. Although the spectrum structure may be conceptually simpler for the case where the timing offsets are compensated, it is by no means clear that either method is better than the other in terms of the output waveform quality. We then apply the results to analyze the direct digital synthesis output sine waves. The signal-to-noise ratio, SNR, for both cases is derived in simple closed form. It is found that for the case where the timing offsets are compensated, the SNR can be greatly enhanced by appropriate selection of operation parameters     

A 12-Mc, Nine-Bit Digital Function Generator

This paper describes some developed equipment found very useful in evaluating circuits that require digital inputs. For example, D-A converters are generally tested by using their associated A-D converter as a test-signal source. Since the A-D converter itself introduces errors, the measurement of analog input and output indicates over-all performance but not individual converter performance. The digital function generator allows separate evaluation of D-A converters by synthesizing useful test functions from discrete samples. Comparison of the known input with the output gives an accurate performance check. The present equipment generates up to sixteen different samples, represented by nine-bit words in parallel form, at a word rate of 12 Mc. A discussion of useful test functions for determining D-A converter linearity and transient response will include discussion of digital sine waves, ramps, and step functions. Although D-A converter evaluation is stressed, the equipment is also useful for other tasks.