Thin-film strain gauge sensors for ion thrust measurement

In order to measure the thrust produced by a stationary plasma thruster, a measurement system has been developed using a thrust balance with thin-film strain gauge sensors. For this purpose, strain gauges were designed and deposited on the columns of the thrust balance fabricated and necessary signal conditioning circuits have been used. The performance of the system developed was studied, in a vacuum chamber under space simulated conditions, by activating the thruster. In situ calibration was done using Lami's principle. For discharge powers varying from 210-275 W, the measured values of thrust were found to be in the range of 11-16 mN with an accuracy of /spl plusmn/1 mN and resolution of 0.12 mN. Specific impulse and efficiency were also estimated.     

Local Particle Mean Velocity Measurement in Pneumatic Conveying Pipelines Using Electrostatic Sensor Arrays

In this paper, a measurement system for the local mean velocity of pneumatically conveyed particles is proposed and developed. It mainly consists of electrostatic sensor arrays, signal conditioning circuits, and a digital signal processor (DSP)-based data acquisition and processing unit. Electrostatic sensor arrays are used to detect the charge on particles in its sensing zone and further make the local particle mean velocity measurement in conjunction with cross-correlation method. The sampling frequency is determined from theoretical analysis of the bandwidth of electrostatic signal and accuracy of correlation velocity calculation. Experiments are carried out on a belt conveyor and a gravity-fed particle rig to determine the optimized sampling number of the electrostatic signal through analyzing the measurement error of the transit time. The results showed that the more sampling numbers, the higher stability of measurement results. The repeatability of the measurement system is less than ±2.2% and the linearity is better than ±4.9% over the velocity range of 5.50–21.98 m/s. Experiments are also performed on a high-pressure dense-phase pneumatic conveying system of pulverized coal, indicating that the measurement system is capable of achieving local mean velocity measurement of pneumatically conveyed particles with the relative standard deviation less than 5.5%.     

脉冲电压信号测量系统

随着电子技术的发展,半导体开关元件的切换频率不断提高。为了检测开关元件在快速切换开关时产生的脉冲电压信号,本文讨论了窄脉冲信号检测的原理和方法,设计并实现了脉冲测量电路。该电路分别采用高速ADC和DDR2存储器进行波形采集和存储,并在FPGA中设计检测电路,通过信号同步触发的形式实现窄脉冲信号的实时检测。实验表明:系统能够有效捕获到脉宽为100纳秒级的信号,且具有较高的幅度精度以及良好的实时性。同时,预触发长度可以通过编程实现。     

A distributed measurement architecture for industrial applications

In this paper, a distributed digital measurement architecture for industrial applications is proposed. The architecture is arranged on three hierarchical communication levels: the fieldbus, the intranet, and the Internet. Particular attention has been paid to the lower level, the field level, implemented using a low-priced smart front-end. It is based on the H8/3048F Hitachi microcontroller and embodies a fieldbus interface (I/F). The same board can be linked to a VXIbus controller by means of a suitable register-based interface. The proposed network can embody a number of analog signal conditioning circuits, processor, and communication capabilities, to meet the industrial needs. We propose two applications of this distributed measurement architecture: the monitoring of power quality in an electrical distribution network and the management of a water distribution system. Experimental results showing the system performance are also included in the paper.     

A Simple Method for the Calibration of Traditional and Electronic Measurement Current and Voltage Transformers

The calibration of measurement transformers represents a classical task in the practice of electrical measurements. Most commercial instruments that are expressly designed for this purpose found their working principle on a scheme that is based on the idea of Kusters and Moore. Although they can assure very high accuracy, the need to employ a high-performance electromagnetic circuit makes them very expensive and usually not suitable for measurements at frequencies that are higher than 50 or 60 Hz. For this reason, these kinds of instruments cannot be employed for the calibration of the new generation of current and voltage transducers, such as electronic measurement transformers, whose employment is growing in all the applications where wide bandwidth is required. In this paper, a new method for the calibration of electromagnetic voltage and current measurement transformers (VTs and CTs) and electronic voltage and current measurement transformers (EVTs and ECTs) is discussed, and a deep metrological characterization is carried out. The novelty of the proposed method is represented by a completely different approach to the measurement of the ratio and phase errors of the measurement transformers. The method is based on the proper digital signal processing of the signals that are collected at the secondaries of the transformer under test and of a reference transformer when the same signal is applied to their primary. Since no auxiliary electromagnetic circuits are required, this solution can be easily implemented in a simple and cost-effective way. In spite of its simplicity, the tests that are developed on a prototype clearly point out that the proposed system is suitable for the calibration of measurement transformers with precision class up to 0.1 in the frequency range from 50 Hz to 1 kHz.     

Designing low-cost modified cladding sensors: a structured approach

In this paper, a novel solution for signal conditioning, fiber illumination, and measurement is proposed for an optical fiber sensor based on a modified cladding sensing element. The presented technique has properties of compactness and low cost, due to the use of very common optoelectronic components, and flexibility, since it could be employed for different kinds of optical fiber sensors. In particular, a prototype has been realized and characterized for the measurement of liquid temperature.     

Stochastic analog-to-digital converter based on the asynchronoussampling of a reference triangle

An analog-to-digital (A/D) converter is presented based on the repeated comparison at random intervals of the input voltage with the instantaneous value of a triangular waveform. This asynchronous sampling of a triangular waveform results in a converter, which features simplicity, both in conversion principle and circuit design, as the linearity merely depends on short-term stability of nonprecision components. The resolution increases with the number of samples and a tradeoff is possible between resolution and conversion time. In intelligent sensors the transducer, the signal conditioning circuits, and the A/D converter are integrated in a single chip. The required IC-process compatibility of all these subsystems narrows the range of the possibilities for implementing special processing steps to realize precision components, which favors the application of the stochastic A/D converter     

Thin-film optical sensors with silicon-compatible materials

Antireflection filters based on multilayer stacks of dielectric and polysilicon films on monocrystalline silicon combined with charge collection in different (poly)Si layers can be used to realize sensors with a programmable spectral response controlled by weighted summing of the photocurrents detected in the polysilicon and the substrate. Thus, employing both interference and selective absorption of light yields increased photoelectric efficiency and improved flexibility of spectral control and enables on-chip integration of the detector(s) with the signal conditioning and processing circuits. The potential of thin-film color sensors has been evaluated for this purpose. However, for practical implementation of such structures the problems associated with the realization of reliable photodetectors in polysilicon must also be considered. Phosphorus passivation of the grain-boundary states has been employed to yield polysilicon photodiodes with improved electrical characteristics and reliable light and color detection. We present the design methods of thin-film color sensors employing silicon-compatible materials only. The measurement results of a fabricated structure fully demonstrate that such sensors can be realized with good spectral selectivity.     

Microinductive Signal Conditioning With Resonant Differential Filters: High-Sensitivity Biodetection Applications

Inductive-based devices integrated with Si technology for biodetection applications are characterized, using simple resonant differential filter configurations. This has allowed the corroboration of the viability of the proposed circuits, which are characterized by their very high simplicity, for microinductive signal conditioning in high-sensitivity sensor devices. The simulation of these simple circuits predicts sensitivities of the differential output voltage which can achieve values in the range of 0.1-1 V/nH, depending on the coil parameters. These very high-sensitivity values open the possibility for the experimental detection of extremely small inductance changes in the devices. For real microinductive devices, both series resistance and parasitic capacitive components contribute to the decrease of the differential circuit sensitivity. Nevertheless, measurements performed using micro-coils fabricated with relatively high series resistance and coupling parasitic effects have allowed detection of changes in the range of 2 nH. which are compatible with biodetection applications with estimated detection limits below the picomolarity range.     

毫米级纳米几何特征尺寸计量标准装置多自由度激光干涉计量系统

准确的纳米几何结构测量是提高集成电路、微纳机电系统和微纳技术产品的质量和性能的关键技术支撑,为了得到准确一致的测量结果,必须实现纳米尺度的量值溯源并建立量值的传递体系。为满足纳米几何结构计量从纳米尺度到毫米尺度的跨尺度计量需求,实验室研制了毫米级纳米几何特征尺寸计量标准装置,集成于该装置中的多自由度激光干涉计量系统,实现了测量结果向米定义SI单位的直接溯源。实验结果表明该系统能够在毫米级的测量范围内,实现纳米级的测量准确度,分辨力达到了亚纳米量级。     

Design and Analysis of a Tri-Axis Gyroscope Micromachined by Surface Fabrication

This paper presents an innovative microgyroscope design. Solely by planar fabrication and wet etching, the proposed microgyroscope is capable to detect three-axis angular rates. The induced motion of individual seismic mass modules are designed to respond in the directions orthogonal to each other in order to decouple the obtained measures. In our work, three pairs of high-resolution differential capacitors with signal processing circuits are employed to measure the angular velocity components in three axes. On the other hand, the drive electrode comb is used to constantly vibrate the outer-ring in tangential direction by sinusoidal voltage. The signal bandwidth about the principle axis is increased by distributed translational proof masses, placed 90$^circ$ apart orderly around a circle. Each individual translational proof mass is designed to move in radial direction so that superior mode matching (i.e., resonance mode) can be easily, to some extent, achieved. The planar suspension flexures are particularly designed in geometry to resist acceleration in drive mode but increase the stroke of tilting angular displacement of the outer-ring such that the resolution of detected angular rate for the corresponding sense mode is upgraded. By considering the complicated geometry of the suspension flexures, finite-element method (FEM) is employed to examine the potential maximum induced mechanical stress. The dynamic equations of the proposed gyroscope are established are well so that the embedded gyroscopic effects are unveiled. More importantly, the efficacy of the drive and sense circuits modules is verified by commercial softwares Hspice and Multisim. By intensive computer simulations and preliminary experimental studies, the resolution, bandwidth and sensitivity of the tri-axis gyroscope are expected to be fairly enhanced if a certain degree of tradeoff is preset.      

Interfacing Differential Resistive Sensors to Microcontrollers: A Direct Approach

This paper introduces and analyzes a novel circuit to directly connect differential resistive sensors to microcontrollers without using either a signal conditioner or an analog-to-digital converter (ADC) in the signal path. This new circuit relies on measuring the discharging time of several resistance-capacitance ( RC) circuits that include the two sensor resistances. Such an operating principle makes the circuit simple, compact, low cost, low power, and accurate. The main uncertainty sources are the quantization of the discharging time measurement and the mismatch of internal resistances of the microcontroller. According to experimental results, the circuit shows errors in the range of 0.01% full-scale span (FSS), and the effective resolution can be up to 13 bits for a measuring time of 100 ms, which are very remarkable considering its simplicity.     

Improved method on image detection at low light level using a sinusoidal-shaped-function signal

This study proposes an improved method which employs the shaped-function technology and Discrete Fourier Series Transform (DFST)-based algorithm to improve the subjective impression at low light level. A sinusoidal wave light signal which is generated in the low frequency range plays the role of a shaped-function signal. The basic procedure of the proposed method is that an LED with a time-varying (sinusoidal) beam is used to illuminate the image sensor evenly. Then, a DFST-based algorithm is employed to remove the sinusoidal wave signal from the captured images for restoring the low-light-level image signal with a low gray resolution. The main purpose of this method was to improve gray-level resolution and signal-to-noise ratio of the acquired image and process the image data in real time by sliding the window. The derivation processes and experiments verify that the improved method not only can reveal a better result than the algorithms we have proposed before, but also have a better performance on the imaging speed.     

基于超声波A/D采样法的相位差位移测量方法

为了提高超声波位移测量分辨率,提出一种基于超声波A/D采样法的超声波相位差位移测量方法,利用超声波信号的相邻采样数据之差,消除了超声波信号中的直流成分对相位差位移测量的影响,再通过不同相邻采样数据之差的比值建立了相位差位移测量的数学模型,由此获得较高的相位差位移测量分辨率。该方法的采样电路简单,不需要高倍数超声波信号采样率,仅需在一个超声波信号周期里采样10几个数据,就可获得亚微米级的位移测量分辨率。实验结果验证了该方法的有效性。基于该方法研制的超声波位移测量平台,若超声波频率选用40 kHz,则位移测量分辨率可达1 μm。     

Temperature measurement in microfluidic systems using a temperature-dependent fluorescent dye

A technique is described for the measurement of fluid temperatures in microfluidic systems based on temperature-dependent fluorescence. The technique is easy to implement with a standard fluorescence microscope and CCD camera. In addition, the method can be used to measure fluid temperatures with micrometer spatial resolution and millisecond time resolution. The efficacy of the method is demonstrated by measuring temperature distributions resulting from Joule heating in a variety of microfluidic circuits that are electrokinetically pumped. With the equipment used for these measurements, fluid temperatures ranging from room temperature to 90 degrees C were measured with a precision ranging from 0.03 to 3.5 degrees C-dependent on the amount of signal averaging done. The spatial and temporal resolutions achieved were 1 microm and 33 ms, respectively.     

基于谐波小波变换的共振解调法

在滚动轴承的振动故障诊断中，广泛使用解调方法分析诊断故障。利用软件方法实现共振解调时，必须首先构造窄带高频带通滤波器，提取高频共振信息，然后利用Hilbert变换进行解调分析。通过分析谐波小波变换的实现过程，发现信号经谐波小波变换的实质是将信号带通滤波后，进行Hilbert解调。另外，共振解调中要求带通滤波器是窄带高频带通滤波器，广义谐波小波突破了传统二进小波在低频分辨率高，而在高频分辨率低的限制，能够实现超窄带高分辨率检波，满足共振解调的要求。在此基础上，提出了基于谐波小波变换的共振解调算法，为软件实现共振解调提供了一种新的途径。     

A Dual-Mode Conditioning Circuit for Differential Analog-to-Digital Converters

Several devices such as load cells and pressure sensors, among others, provide differential outputs. Given that present high-resolution analog-to-digital converters (ADCs) have differential inputs, fully differential (F-D) circuits are required to adapt the sensor output to the ADC input. This paper proposes an F-D conditioning circuit that allows adjusting both differential- and common-mode signals to the levels required by the ADC. A design example is presented, and a prototype was built and tested. It transforms a differential input signal of $pm$25 mV with a common-mode voltage of 5 V to a differential output signal of $pm$5 and 2.5 V, respectively. It shows an input-referenced peak-to-peak noise of 120 nV, which results in a 112-dB dynamic range (18.7-bit noise-free resolution) for a signal bandwidth of 10 Hz.      

On-chip rise-time measurement

The on-chip rise-time measurement method for an exponentially decaying signal is proposed. By employing a differentiator, the method circumvents the challenges associated with directly measuring a signal's rise time. The method can be used as the on-chip test instrument as part of a built-in self-testing (BIST) framework, or independently. CMOS circuits and layouts for implementation of the proposed method on a 0.25-/spl mu/m technology have been developed.     

一种电感式位移传感器的电路系统设计

介绍了一种电感式位移传感器的电路系统.该系统以一片AD698芯片为信号调整电路的核心,将位移量输出信号转换为相应的直流电压值,并结合其它一系列电路模块实现了测头位移量测量.通过对测头的标定试验证明该系统精度高、线性测量范围大.     

Research on coding and decoding method for digital levels

A new coding and decoding method for digital levels is proposed. It is based on an area-array CCD sensor and adopts mixed coding technology. By taking advantage of redundant information in a digital image signal, the contradiction that the field of view and image resolution restrict each other in a digital level measurement is overcome, and the geodetic leveling becomes easier. The experimental results demonstrate that the uncertainty of measurement is 1 mm when the measuring range is between 2 m and 100 m, which can meet practical needs.