A dynamic error model for integrating analog-to-digital converters

Integrating analog-to-digital converters (IADCs) basically include an analog signal processing section for conditioning and integrating the input signal, and a quantizing section for obtaining the digital converted signal. The main dynamic errors arise from the analog signal processing section. In this paper, the resulting dynamic integral nonlinearity of IADCs is analytically derived and a model based on a low-order polynomial function of the input signal slope and the output code is proposed. The analytical model is useful for reducing experimental burden related to dynamic metrological characterisation. Experimental validation results highlight the model effectiveness in describing integral nonlinearity of an actual dual-slope IADC.     

时分复用数字闭环电容式微加速度计接口电路

为实现电容式微加速度计的数字输出闭环,设计了一种数字输出闭环ASIC(Application Specific Integrated Circuit)接口电路,以降低电路输出噪声并提高测量量程。对已有的电容式微加速度计ASIC电路进行了改进,分时段在中间极板上加载差分电容读出信号和由脉宽调变(PWM)波控制的反馈信号,然后由控制器实现闭环,利用Sigma Delta调制器实现模数转换。通过分析差分电容读出电路和Sigma Delta调制器的原理和特性,建立了该数字输出闭环电容式微加速度计的模型,进行了系统的设计与仿真。实验结果表明,该数字输出闭环电容式微加速度计的噪声水平为9.6μg/√Hz,量程为±3g。这些结果验证了时分复用方案的可行性和本文所提出模型的正确性。     

Digital Lock-in Amplifier Based on Microcontroller

A method of implementing high cost-effective and highly integrated digital lock-in amplifier with microcontroller is discussed. And the digital lock-in amplifier is more suitable for measuring low-frequency weak signal.Digital signal sequence is obtained through sampling signal measured over an integer number of signal periods, but digital reference sequence is acquired through mathematical operation, then digital phase sensitive detection can be implemented by calculating the cross-correlation function of digital signal sequence and digital reference sequence.In addition, the frequency response and phase character of the digital lock-in amplifier is analyzed. Finally, the designed digital lock-in amplifier is achieved. Experimental results show that the digital lock-in amplifier can be used for measuring weak signal with low ignal-to-noise ratio.     

线阵CCD智能系统

介绍了线阵CCD(电荷耦合器件)测量系统中的智能化控制、信号处理技术。用可编程定时/计数器8254构成线阵CCD光积分控制信号周期的数字调节器。对线阵CCD输出信号进行模数转换,由DSP(数字信号处理器)对其进行数字信号分析,实现线阵CCD系统的智能化。     

线接触弹流问题弹性变形方程的数字信号解法

根据数字信号系统的分析方法,提出了与弹性体受力变形对应的信号系统模型,在时域和频域内对该系统加以描述。利用信号分析的快速傅里叶变换及其卷积性质,实现了线接触弹流问题弹性变形方程的快速计算,其计算工作量为O（Nlog2N）。对Hertz压力分布接触区弹性变形的计算表明,弹性变形方程数字信号解法的精度与变形矩阵法相当,而计算量及存储空间的开销则大大低于变形矩阵法。因而,弹性变形方程的数字信号解法在弹流计算中具有实用价值。     

以W77E58CPU为核心的皮带秤仪表设计

按照结构化系统开发方法详细介绍了以W77E58CPU为核心的皮带秤仪表设计的开发过程,通过A/D转换将质量信号转换为数字信号,与皮带速度信号进行积分,经数学模型计算实现皮带连续累计计量,并通过RS-485总线实现计量数据的远程共享与远程控制。     

A DSP-based signal processing method and system for CMF

A set of digital signal processing method is formed by combining a digital band-pass filter, an adaptive lattice notch filter and the DTFT algorithm considering negative frequency contribution for processing the signals of Coriolis mass flowmeter. A digital Coriolis mass flow transmitter is developed with a DSP chip to realize the signal processing approach. Some effective measures are proposed to ensure high accuracy and real time of this approach in the implementation. Simulations, electrical signal tests and water flowrate calibrations are conducted to validate the performances of the method and the system.     

基于LabVIEW的数字滤波器设计

虚拟仪器代表着目前测试仪器领域的发展方向,LabVIEW是一种功能强大的虚拟仪器开发平台。数字滤波技术是数字信号处理的一个重要组成部分,滤波器的设计是信号处理的核心问题之一。本文介绍了基于LabVIEW设计数字滤波器的方法,并给出了设计实例。在LabVIEW环境下可以随时对比设计要求调整参数,有利于数字滤波器设计的最优化,有效地克服了传统设计方式中存在的滤波器系数不易调整、与硬件接口程序复杂、开发周期长等问题。LabVIEW为设计数字滤波器提供了一个可靠而有效的途径。     

Research on iterated Hilbert transform and its application in mechanical fault diagnosis

Multicomponent AM–FM demodulation is an available method for machinery fault vibration signal analysis, so a new method for mechanical fault diagnosis based on iterated Hilbert transform (IHT) is proposed. The principle of computing the asymptotically exact multicomponent sinusoidal model for an arbitrary signal by iterating Hilbert transform is introduced, and some properties of IHT are analyzed. Theoretical analysis for the generic two-component signal shows that there are limitations in the direct estimation of instantaneous frequencies via the phase signals of the previously obtained model. Therefore, a smoothed instantaneous frequency estimation (SIFE) method based on difference operator and zero-phase digital low-pass filtering is proposed, and then the accuracy and validity of this method have been proved by the simulation results. The analysis results of the mechanical fault signals show that the weak features of these signals can be efficiently extracted with the proposed approach.     

超低频振动台数字化改造

通过改善振动台标定系统的线性来减小其信号失真度是振动台标定系统的一个关键问题,对振动台标定系统实现数字化标定是技术上的重要发展趋势。本文提出采用主频信号提取技术去除由振动台标定系统的非线性引起而产生的噪声信号和减小振动台标定系统的信号失真度。本文同时提出了一种局部细化傅立叶变换方法和采用了数据库来管理振动台对振动仪器的标定结果,编写了数字化标定软件,设计了采集仪,从而实现了XS型超低频振动台标定系统的数字化改造,提高了标定结果的精度。     

A microcontroller-based lock-in amplifier for sub-milliohm resistance measurements

This paper presents a novel approach to the design of a digital ohmmeter with a resolution of <60 μΩ based on a general-purpose microcontroller and a high-impedance instrumentation amplifier only. The design uses two digital I∕O-pins to alternate the current through the sample resistor and combined with a proper firmware routine, the design is a lock-in detector that discriminates any signal that is out of phase∕frequency with the reference signal. This makes it possible to selectively detect the μV drop across sample resistors down to 55.6 μΩ using only the current that can be supplied by the digital output pins of a microcontroller. This is achieved without the need for an external reference signal generator and does not rely on the computing processing power of a digital signal processor.     

一种光栅莫尔信号数字锁相细分方法

为了保证和提高光栅传感器在动态测量过程中信号细分结果的准确性和实时性,本文提出一种新型的莫尔信号数字锁相细分方法。该方法采用开环结构,根据光栅莫尔信号的实时频率,利用小数分频方法完成对光栅莫尔信号的细分功能;开发了基于现场可编程门阵列(FPGA)的数字锁相细分电路,并对细分实现过程中的电路关键环节进行详细分析;使用自制的细分电路板分别验证了以信号发生器和实际信号为输入的细分算法有效性,并且将改进数字锁相细分方法与传统锁相细分方法进行细分效果对比,实验结果证明,本文设计的数字锁相细分算法能够在更高的莫尔信号频率和频率变化率情况下完成细分功能,因而能够更好的应用于动态测量场合。     

自适应量化嵌入数字水印的音频隐密通信方法

本文提出了一种基于数字水印的音频隐秘通信方法。鉴于隐藏效果的直观性。原始水印信息以二值图像为例,也可为其他类型如语音。该算法首先对有具体含义的原始水印信息进行预处理。使之成为适于嵌入音频的一维数宇水印序列;然后对音频载体分段,根据各段能量大小选定隐藏段。再对各段进行离散余弦变换（DCT）;考虑到不可见性和鲁棒性的折中。本文依据噪声模型确定的噪声敏感度因子在DCT域的中低频系数区选定具体嵌入位置;并采用量化嵌入方法,可实现盲提取。实验结果表明该方法具有良好的不可见性和鲁棒性,能抵抗滤波、重采样、重量化、加噪声等常规信号处理攻击。     

Automation of extrusion of porous cable products based on a digital controller

This paper presents a new approach to designing an automated system for monitoring and controlling the process of applying porous insulation material on a conductive cable core, which is based on using structurally and parametrically optimized digital controllers of an arbitrary order instead of calculating typical PID controllers using known methods. The digital controller is clocked by signals from the clock length sensor of a measuring wheel, instead of a timer signal, and this provides the robust properties of the system with respect to the changing insulation speed. Digital controller parameters are tuned to provide the operating parameters of the manufactured cable using a simulation model of stochastic extrusion and are minimized by moving a regular simplex in the parameter space of the tuned controller.     

通信系统中的特殊机电元件“电触点”

本文根据电接触理论结合高频传输的特点建立了电触点的物理模型,从理论上分析探讨了数字通信系统中电触点故障可能造成的对数字信号传输的影响。     

数字超声无损评价系统中的脉冲噪声

在用数字超时接接头评价时发现,噪声是微弱超声信号检测的主要障碍。建立数字超声系统的物理模型,分析声学噪声和非声学噪声,提出消除脉总噪声的极值滤波算法。实验证明,该算法简单高效,能有效地去除脉冲噪声,且保持领事的有用分量不受滤波影响。     

IBIS模型的信号完整性研究与仿真应用

针对IBIS模型的正确应用,提出了快速验证IBIS模型的准确性以及IBIS模型在信号完整性分析中的仿真方案.首先介绍了模型中数据之间的一种隐含联系,能快速检验所获取IBIS模型的正确性;其次对光纤测温系统进行了基于IBIS模型的信号完整性仿真分析,从IBIS模型中提取引脚的输出阻抗进行反射仿真,然后,在相同线宽的条件下...     

A new signal processing technique for detecting flaw echoes close to the material surface in ultrasonic NDT

A new signal processing technique for separating the reflection of a flaw near a surface from the surface reflection itself is proposed. The method is based on ultrasonic scattering energy function model of flaw close to the material surface. Flaw sensitive component in the model, which corresponding to the low frequency signal, is remained by using a low pass digital filter. In order to make the recognition procedure easier and enhance the recognition effect, a reference signal is introduced to avoid the influence of the surface echo. Thus, the surface flaw is easily and clearly recognized. The good performance of the approach is experimentally verified in laboratory on a steel sample with different man-made surface flaws.     

基于PC机的方波信号周期测试方法研究与应用

给出了用 PC机测量方波信号周期的两种测试方法 :一种是将方波信号作为模拟信号送入计算机 ,通过 A/D转换为数字信号后再经过相应计算得出方波信号的周期 ;另一种是将方波信号作为开关量送入计算机 ,通过软件计数的方法直接得出方波信号的周期。同时 ,对这两种方法进行了较为详细的比较研究 ,指出了这两种方法各自的优缺点 ,并给出了一些应用实例     

基于FPGA的简易数字信号传输性能分析系统

基于 FPGA 产生伪随机信号和曼彻斯特编码,以 MSP430为基本功能控制单元,通过三路低通滤波器和伪随机信号信道噪声来模拟传输信道,设计了一个以数字信号发生器,模拟传输信道和数字分析电路为核心的简易数字信号传输性能分析系统,实现了数字信号传输特性测试.测试表明系统工作稳定,输入信号动态范围大,眼图清晰,达到了设计要求.