LCR自动测试系统

ZL5型智能LCR智能仪是具有标准IEEE－488接口的电感、电容和电阻测量仪器。应用PCL－848A／B多功能IEEE－488接口卡组建了由PC机和ZL5组成的LCR自动测试系统，不但实现了ZL5的基本测量功能，而且扩展了成组测量、数据分析、曲线绘制、打印输出等诸多功能。该系统已有效地应用于湿敏元件的特性测试之中。     

基于IEEE—488接口的RLC测量仪与计算机接口的应用

介绍了基于ＩＥＥＥ－４８８接口ＲＬＣ测量仪与计算机接口的方法，分析了运用ＰＣ进行数据采集的采集软件，特别给出了一种Ｗｉｎｄｏｗｓ ＶＢ环境下进行数据采集的方法。     

Fault coverage in plant protection systems

Many process plant protection systems rely on redundancy methods to achieve high reliability and predictable operation. The basic principle behind such systems is: if one system fails, redundant mechanisms that can allow continued operation or bring the process to a known safe state. It has been shown [1] that the degree of dependability achievable by such systems is a function of the number of “covert” faults—i.e., faults that are not discovered during normal operation and could lead to improper operation of the system on demand if not discovered by testing.

Typical redundant systems automatically test for covert faults using a variety of hardware and software diagnostic methods. “coverage factor” (or simply “coverage”) is a measure of how well such a system detects faults. Therefore, systems with high coverage have few undiscovered covert failure modes and can operate predictably. Systems with low coverage have many covert failure modes and expose the plant to potentially unpredictable and unsafe operation. This paper presents the concept of coverage, explores its impact on system reliability, and discusses methods of achieving high coverage and assessing the coverage factor.     

基于PC总线与GPIB总线的光电设备自动测试系统

将基于 PC总线的 DI/O、A/D、D/A接口卡和 GPIB总线的 HP程控测量仪器集成 ,控制被测电子仪器的测试流程 ,实现了电子仪器测试的自动化 ,并在光学仪器测试中通过串行通信实现了光学数据的计算机获取。最后对测量数据用傅立叶谱分析、小波分析等进行处理 ,并以测量不确定度形式给出了测试结果。     

An Automated Dual-Wavelength Spectrophotometer Optimized for Phytochrome Assay

ABSTRACT

A microcomputer-controlled dual-wavelength spectrophotometer suitable for automated phytochrome assay is described. The optomechanical unit provides for sequential irradiation of the sample by the two measuring wavelengths with intervening dark intervals and for actinic irradiation to inter-convert phytochrome between its two forms. Photomultiplier current is amplified, converted to a digital value and transferred into the computer using a custom-designed IEEE-488 bus interface. The microcomputer calculates mathematically both absorbance and absorbance difference values with dynamic correction for photomultiplier dark current. In addition, the computer controls the operating parameters of the spectrophotometer via a separate interface. These parameters include control of the durations of measuring and actinic irradiation intervals and their sequence. Because the data are processed solely within the microcomputer, except for the initial linear amplification, any output desired can be obtained, including automated determination of not only total phytochrome content, but also of the proportions present in the far-red- and red-absorbing forms.     

Continuous Scan, a method for performing modal testing using meaningful measurement parameters; Part I

This paper presents the first part of a work about modal testing using meaningful measurement parameters. Scanning Laser Doppler Vibrometer (SLDV) systems are becoming largely used both in industry and university for performing vibration measurements. A reason for the success of SLDV systems can be found in their capability of measuring vibration remotely and under different environmental conditions which, when hostile, can inhibit other transducers to work correctly. Hence, SLDV system can be very practical and useful in many engineering applications. SLDV systems are being used as a contactless transducer measuring vibrations from a discrete number of measurement positions marked on the specimen whenever an optical access to it is available. Hence, the advantage of a modal test carried out using accelerometers and one carried out using a SLDV system can be: (i) the automation of the measurements and (ii) the increase of the spatial resolution of the measured modes. This suggests that SLDV systems can be used as a practical replacement of accelerometers operating the same measurement method. Continuous Scanning method is a novel approach of using contactless transducers for measuring vibrations. The most important difference between a discrete and a continuous approach is the method of measuring a vibration pattern. A discrete method measures the level of vibrations at discrete positions on a structure whereas a continuous method captures the modulation of the vibrations produced by the excited modes. This is possible when a transducer can travel across a vibrating surface. This first part of the work presents a new approach of continuous scanning measurement method using a multi-tonal excitation waveform. The paper starts from a comparison between a step and continuous scan mode to introduce a novel approach of continuous scan and multi-tonal excitation waveform. The objective of this first part of work is to present and understand that measurement parameters, such as measurement positions, and can be carefully chosen to improve the measurement technique. A laboratory test piece and a helicopter tail cone are used as examples for the application of this new measurement method approach.     

A system approach to electrical measurements

The essential idea of the system approach to electrical measurement is uniform treatment of measurement problems and/or instruments, which can be considered as special cases of a system whose functions are performed via signal processing. Recent achievements in the domains of digital signal processing, microelectronics, micro-machining and micro-optics enable one to improve the quality of measurements by means of sophisticated algorithms of signal processing implemented using VLSI technology and by means of microsensors. The integration and the design of measuring systems requires, in general, significant interdisciplinary contributions, and computerized design tools should generally be used for this purpose. Under such circumstances, this approach becomes particularly effective for understanding, designing and teaching measuring systems.     

How to teach at the university level through an active learning approach? Consequences for teaching basic electrical measurements

This paper is an updated (August 2004) and enlarged version of a keynote lecture presented at the 2002 IMEKO TC-1 International Conference “Education in Measurements and Instrumentation – Challenges of New Technologies”, Wroclaw, Poland, 9–10 September 2002.

A completely new engineering curriculum has been progressively introduced since 2000–2001 at the Université catholique de Louvain in Belgium with a modern educational approach which strongly emphasises active learning based on projects and problems. The paper will, as an introductory part, present the whys, whats and hows of this revolution. An example of a multidisciplinary project at graduate level will be outlined.

As the consequence of this new teaching context, the place for traditional lecture courses is reduced to a small portion of the curriculum. It is against a background of limited time that a re-centring is needed in terms of what subjects are essential to provide a basic training in electrical measurements and instrumentation for every student in electrical and electromechanical engineering. The paper will draw up a list of un-circumventing topics to be taught, accompanied by appropriate comments.

We conclude with the presentation of a laboratory exercise in basic electrical measurements illustrating the new educational method by its problem-based learning approach.     

Getting familiar with map in the process industries

Even Parity? Old Parity? Polynomial Checksum? Vertical Byte Parity? BCH Check Code? Cyclical Redundancy Check Code? These are just some of the communication formats currently being used to send information between computers within a network. Whenever a supplier provides a system, a “proprietary” or peculiar protocol is established to operate between the elements of the network. When it is desired to interconnect digital equipment of two or more suppliers, a “custom” interface is required. As long as the two suppliers do not revise their native codes, the custom interface can be reproduced for another application.

MAP is a standardized communication format intended to eliminate the wide variety of proprietary formats and the need for custom interfaces between different suppliers of digital equipment and systems. Thus, the term “open” systems interconnect (OSI) and interoperability have been popularized to represent this emerging technology.     

Automated apparatus for evaporation and in situ measurements of multiple thin films

We describe a system for vacuum deposition which measures as well as controls substrate temperature, film thickness, and rate of evaporation. By measuring the resonant frequency of a quartz crystal oscillator which has been calibrated for thickness, we produce films of 11 different thicknesses in a single evaporation. The system is then capable of immediately initiating four-probe resistivity measurements on the evaporated films every 90 s, allowing the measurement of rapid structural changes. The system is calculator-based and interfacing is achieved with plug-in compatible instrumentation using the IEEE standard 488-1975 interface bus.     

岛津ICPS—1000 Ⅱ型光谱仪数据处理系统的升级改造

通过对岛津ICPS-1000Ⅱ型等离子体光谱仪数据处理系统的升级改造,使用PC系列微机,插入IEEE-488并行通讯接口卡,替代原三菱MULT116计算机,实现了对ICPS-1000Ⅱ光谱仪主机的控制。将原软件移植成功,并加入了一些功能和删除了一些不必要的操作。进一步开发了该仪器的功能,使其维修、维护和应用变得方便、快捷。     

基于虚拟仪器的齿轮箱噪声检测系统设计

通过对齿轮箱噪声的检测及分析来了解齿轮箱齿轮的运行状态并诊断其故障原因;利用NI公司提供的接口硬件及通用的声音采集仪器,在LabVIEW的软件平台上设计一套可行的齿轮箱噪声在线检测系统,并在实际的齿轮箱状态监测试验中得到验证。     

Standardisation of DAQ systems with regard to EMC

The precision of dynamic measurement using modular DAQ systems is dependent both on the dynamic parameters of the AD module used, and the EMC conditions in the system case. This can cause difficulties in the correct use of commercially available products. The disturbing magnetic field and disturbances propagating over supply lines cause a decrease in the real effective number of bits of an AD module. Real disturbing fields which influence AD modules have been measured so far in PC systems and in notebooks (for transportable systems), but the method can also be used for other modular DAQ systems. The next source of disturbance — an AC component of supply voltages — was measured in several types of PCs to investigate typical parameters of disturbance propagating over supply lines. The methods for disturbance immunity measurement of AD modules were designed and the system for testing PC plug-in boards with ISA or PCI interface and PCMCIA cards was developed. To describe the disturbance immunity of different types of AD boards, a disturbance immunity factor DIF was defined. All measured values can be used as a base for a limit determination of conventional environments in system cases.     

基于HP34970A数据采集仪的计算机测控系统设计

介绍了基于HP34970A数据采集仪和GPIB总线构建的计算机测控系统,并以制冷空调综合实验系统为应用实例,从硬件结构和软件设计方面阐述了该系统的实现原理。此外,还就实时监控程序的设计进行了重点讨论。     

Ball array calibration on a coordinate measuring machine using a gage block

The distances between the balls of a ball array used in machine geometry calibration have to be very accurate. These distances can be calibrated using a laser measurement system, which requires specially designed optical devices and measuring probes. In this paper, a new and economical alternative method for calibrating the ball array is described. A single gage block is used for measuring the standard distance at the starting position. Then, the exact distances between the balls can be obtained by using the coordinate measuring machine (CMM) probe motion. This method does not depend on the accuracy of the CMM. Also, this method does not require expensive instruments or devices, but a CMM and a gage block. A simple “parallel-plane” bracket, mounted on to the measuring end of a CMM probe, is used to determine the centers of the balls automatically and accurately.     

User interface for optical multi-sensorial measurements at extruded profiles

Nowadays the process control of concave extruding is a measuring task with rising requirements. A novel optical bi-sensorial measurement system - consisting of a shadow- and a light-section-system - as well as suitable methods of analysis for the in-line inspection are presented. The proposals help to ensure the product quality on a higher level than before. The combination of dimensional accuracy and data-density leads to excellent results. The optical multi-sensor measurement system has to be calibrated and aligned to detect the same surface zone despite of high refresh rates and optical resolutions. The metered characteristics will be coordinate transformed to extrinsic world-coordinates for evaluating form deviations of complex parts. An appropriate user interface enables to re-calculate measurement objects in-line and evaluate the conformity of the part consequently. Finally the real length information assists to influence the process control. After successful test in laboratory the results will be proved in production to the target: measurement uncertainty of better 0.1 mm at every profile.     

A non-steady-state probe measurement method to determine heat conductivity, heat capacity as well as moisture in solids and bulk materials

It is important to know the heat conductivity coefficent for an effective use of energy, for quality control of many products or numerical simulation of heat transfer problems. Measurement of heat conductivity should be realized with high reliability and accuracy, in a short time and with low expenditure both in the laboratory and in situ at the production process, to be able to influence the current process. A non-stationary probe and measurement method developed at Dresden University (Institute of Thermodynamics and Human Engineering) allows the determination of heat conductivity, heat capacity as well as water content of solid and bulk materials. Comparative measurements on standard materials and expert opinions of various institutions confirm the high accuracy and the reliability of the non-steady-state probe measurement device also in so called “problematic” materials.     

A NOVEL VARIABLE RATE PNEUMATIC FERTILIZER APPLICATOR

The canopy prevents the use of global positioning system based fertilizer applicators in oil palm plantations. Hence, a radio frequency identification triggered variable rate pneumatic fertilizer system was developed for this application. A real-time embedded system was used as the core controller, LabVIEW software was used to program and coordinate the operations of the embedded system and the host computer. A speed measuring unit was used to provide feedback to the system. A field test was conducted to examine the response time. The sensors were calibrated in the laboratory and the measurement linearity had regression coefficients close to 1. Two to three seconds were required for the device to respond to changes in application rate. It is expected that this approach will become an alternative in plantations where the canopy hinders proper application of global positioning systems.     

Development and validation of a new reference cylindrical gear for pitch measurement

A new type of master gear, the Gauge Block Gear (GBG), was developed for the performance verification of coordinate measuring machines (CMMs), for the specific task of pitch and chordal tooth thickness measurement. Its main characteristic is the replacement of the teeth with gauge blocks to achieve direct traceability of the chordal tooth thickness. Mathematical models for the geometrical definition of cylindrical gears with involute toothing, data evaluation, and assessment of the task-related uncertainty, were formulated, and measuring strategies for CMMs were designed and implemented. The GBG was calibrated using the swing round method, and measurement uncertainties on chordal tooth thickness and total pitch deviation F_p were determined to be 0.9 μm and 1.4 μm, respectively. Assembly stability and flexibility of the artefact were verified with measurements performed on a CMM provided with general purpose software, one with dedicated gear measuring software, a form tester, and a conventional gear measuring center. Results confirm the correctness of the mathematical models developed to analyze CMM results as well as their compatibility with existing approaches. The Gauge Block Gear provides, therefore, for direct traceability of the chordal tooth thickness and allows the definition of the task-specific uncertainty of pitch and tooth thickness measurements of cylindrical gears as basis for the assessment of the metrological capability of measuring machines.