Audio Precision音频测试仪的音频测量方法(1)

音频测量是音频相关从业人员在日常工作中经常遇到的一个环节,通过音频测量,可以检验设备或系统的音频指标,从而判断其优劣。当设备或系统发生故障时,也可借助音频测量来帮助我们查找故障点。结合实际测试中的经验及教训,详细介绍了采用Audio Precision音频测试仪测试常用音频参数的测试方法。     

更多的ADC指标

人们经常会把模数转换器(ADC)的无寄生动态范围(SFDR)和信噪比(SNR)混淆,我们之前在"了解ADC SFDR指标(Understanding ADC SFDR Specs)。"(http://designnews.com.cn/0902-116. aspx)一文中曾经介绍过这一概念。SFDR描述了     

一种新型的大动态范围CCD相机视频信号处理电路

由于目前的CCD尤其科学级CCD的动态范围高达105:1,甚至106:1,此时若要满足ADC的动态范围大于CCD相机的动态范围,则必须选择分辨力为18～20bit的ADC,而航天级或高等级的高分辨力ADC较少且价格昂贵。本文利用CCD相机系统的噪声谱密度跟信号大小有密切关系这一特点,对于强光信号和弱光信号采用不同的信号处理链,从系统通道增益的角度阐述了低分辨力ADC实现高分辨力模数转换的原理及硬件实现方案,最后通过实验室成像测试验证,实验结果表明,用低分辨力A/D转换器采用粗细量化相结合方式实现了高分辨力模数转换,并提高了CCD相机的动态范围。     

基于Matlab的ADC自动测试系统开发

阐述了模数转换器的静态参数和动态参数测试原理和方法,并且构建了模数转换器的自动测试硬件平台和软件系统.重点讨论了利用Matlab库函数进行快速傅立叶变换测试的方法,使用ADC自动测试系统对高速模数转换器SCM530101进行了测试,并给出了测试结果.     

基于自动测试系统的数字电路板测试与故障诊断

文章讨论了数字电路板故障诊断的原理和方法,介绍了自动测试系统在数字电路板测试与故障诊断中的应用,阐述了运用自动测试系统进行电路板故障诊断的结构。     

基于Excel测试模板的变频器自动测试程序设计

变频器作为微波信号发射端和接收端的重要器件,对收发系统性能具有较大影响,因此,需对相关参数进行测试。本文针对其种类、测试参数和测试仪器设备多,以及测试人员要求高、人工测试效率低,开发设计变频器自动测试程序,并基于Excel测试模板,实现定制化测试。     

基于GPIB的电源自动测试系统的设计

介绍了基于GPIB总线技术的电源参数自动测试系统,详细阐述了系统的硬件组成和软件编程。该系统不仅具有高的测量效率和测量精度等优点,而且结构灵活、可扩展性好,满足各种电源的测试要求,经使用验证,可应用于实际生产中。     

照明用大功率无桥LED驱动电路输入电流谐波分析

对作者介绍的照明用大功率无桥LED驱动电路的输入交流工频电流波形在设定电路条件后的频谱和谐波含量进行了分析和计算,其结果是,在电路最低工作频率以下的频率范围内基本不存在谐波成分,电路输入电流的总谐波含量THD随最小输入电流脉冲宽度T₀(min) 增大而上升,随电路的输出直流电压与输入交流电压有效值的比U_o/U_i的增大而下降.并指出在电路的输入端需要一个滤波电路,分析了滤波电路的滤波效果,给出了滤波电路的设计方法.     

基于机载通信自动测试系统的智能手动测试系统设计

为了解决机载被测设备可测性较低与测试自动化需求较高之间的矛盾,本文提出了基于某型机载通信自动测试系统平台建立智能手动测试系统的思想.同时给出了手动测试解决方案,并在现有自动测试平台上实现了智能手动测试软件的设计与开发.     

Utilization of operational amplifiers for raising the input impedance of measuring circuits

Summary The analysis and testing of a matching circuit consisting of two operational dc amplifiers have shown that it is possible by means of this circuit to match dc voltage circuits with a large internal resistance (up to 10 meg) to circuits with a small internal resistance (up to 10 kohm).     

Long-term behavior of operational amplifiers

The voltage and current offsets of two typical precision operational amplifiers (OPAs) with BJT and FET input, respectively, were continuously measured for two years. The paper presents the experiment, explains the method of data analysis, and discusses the results. The long-term stability turns out to be limited mainly by random walk processes     

Applications of operational amplifiers in strain gauge circuits

Operational amplifiers, originally developed for analogue computation, are now widely used in analogue instrumentation, signal conditioning, servo controls, voltage and current regulators and an extensive range of other functions. In experimental mechanics, operational amplifiers are ideally suited to applications involving strain gauges. Both Wheatstone bridge and ballast (potentiometer) circuits are examined together with the limitations and constraints imposed by amplifier and external circuit considerations. These limitations are important, whether relatively simple operational amplifiers or the more complex instrumentation amplifiers are used. Many manufacturers provide a wide range of 'off-the-shelf' integrated circuit and discrete amplifiers, together with comprehensive specifications, permitting selection of a suitable device. Before discussing strain gauge applications, the properties of operational amplifiers will be reviewed briefly.     

Evaluation of ADC testing systems using ADC transfer standard

A transportable high-stability reference AD device was designed and built to compare the systems for testing the dynamic quality of analog-to-digital converters (ADCs) or analog-to-digital (AD) modules. Three different input modules can be used in the frequency range up to 5 MHz. First, this paper refers to the results of an AD device application in the frequency range of the testing signal up to 100 kHz, where four ADC testing systems were compared in different laboratories, and a short time amplitude and/or frequency instability of testing signal generators was evaluated. Second, it describes the first experience of its application in the frequency range from 100-5 MHz.     

High-speed voltage buffers for the experimental characterization ofCMOS transconductance operational amplifiers

Two voltage buffers realized with discrete components are presented which provide very low input capacitance and input bias current, high-frequency capability and low-output resistance. This performance means they are well suited for employment in the characterization of operational amplifiers and specifically CMOS transconductance operational amplifiers     

Windows for ADC dynamic testing via frequency-domain analysis

In this paper, the frequency-domain dynamic test of analog-to-digital converters (ADCs) is considered under the assumption of noncoherent sinewave sampling. A procedure is described which is based on the windowed discrete Fourier transform (WDFT), optimized for the achievement of high estimation accuracy. With this aim, the class of windows belonging to the set of discrete prolate spheroidal sequences is adopted for the reduction of the effects of spectral leakage. Practical suggestions are given for a straightforward applicability of derived results and for an efficient estimation of ADC spectral parameters. Finally, experimental results are presented in order to validate the proposed testing approach     

Systematic design of programmable operational amplifiers with noise-power trade-off

A methodology for the systematic design of a programmable operational amplifier (opamp) is described. With this methodology, the opamp is programmable concerning noise and power consumption while keeping the stability for the whole operation range with a constant phase margin of phi_res=70deg. The theoretical model is developed with the help of the transfer characteristics of the opamp determining the degrees of freedom. Experimental results for a 0.35-mum CMOS opamp show either ultra low-noise of 2 nV/radicHz or low-power consumption of 140 muW while keeping the opamp stable over the whole range of programmability