Cutting costs of compliance [EMC testing]

Simple and inexpensive in-house test procedures and instrumentation can save a great deal of time and cost in EMC certification. The author discusses the role of precompliance testing and practical approaches, including instrumentation, to this form of testing     

Cradle to the grave [EMC testing]

The EMC Directive has had a direct and far reaching effect on manufacturers. Unfortunately, manufacturers often fall into the trap of considering that it is sufficient to demonstrate compliance for a single unit. The reality of EMC compliance requires the implementation of a total EMC approach to the business process, with compliance an integral part of the product life-cycle. Continuing compliance involves a variety of business disciplines not normally considered to be involved in the EMC process. The business framework requires that EMC codes of practice and quality assurance systems are fundamental at all stages of apparatus design, development, approval, procurement and production. In addition, procedures should be in place which address ongoing compliance up to the withdrawal of the product from the market. The author outlines the strategies, frameworks and policies required to manage EMC from concept to completion     

Panel games [control panel EMC]

EMC may not strictly be a legal issue for manufacturers of control panels, but their customers are increasingly insisting that they demonstrate compliance. Here, the author describes how control panel builders and system integrators can work together to achieve EMC, and the role of the technical construction file     

Happy medium [EMC CAD tools]

Electromagnetic compatibility is becoming an important element in the design of virtually all equipment and systems connected to an electrical supply. Contemporary design practice is increasingly reliant on the use of computer-based tools to realise the maximum degree of automation in the design process. This trend is set to continue. Furthermore, in the design of complex systems, interactions between different facets of the design problem make concurrent engineering practices mandatory. In practice, irrespective of its technical capabilities, ease of use and cost of deployment are critical factors in determining the success of any design tool. If a CAD package is to be widely used within industry then it must be both user friendly and capable of running quickly on modest PC platforms; at the same time, offering the user the maximum possible physical insight into the nature and magnitude of the interactions affecting the design. This article describes an approach to EMC CAD tool development, based on collaborative work between the universities of York and Nottingham, which is designed to meet these exacting requirements     

No longer an option [EMC legislation]

From 1 January 1996 the European EMC legislation becomes fully effective and in theory, it will no longer be possible to market products that do not comply with the protection requirement of the EMC Directive. There have been six years of discussions and prevarication related to the issue. The author discusses the state of EMC in the UK as the deadline approaches based on a survey of IEE and EMC Club members. An inset covers the questions and answers of a Yorkshire and Humberside EMC Club meeting     

On track for compliance [railways, EMC]

Railways provide a good example of the importance of achieving compatibility between electrical and electronic systems. It is all too apparent that interference from traction power equipment may affect signalling systems with potentially dire consequences. So in the UIC, EMC is one of the requirements to be included in the safety case for the introduction of new rolling stock, locomotives or track maintenance vehicles. The author discusses the key EMC problem of the multi-functional role of the rails and then discusses the way in which the railway EMC standards and compliance issues work in practice. The examples of the class 57 locomotive, the Plasser+Theurer Flashbutt welder, track maintenance vehicles, and electric multiple units, are discussed     

Early bird catches silver lining [EMC compliance]

The author outlines the response of Seaward Electronic Ltd. to the European Directive on Electromagnetic Compatibility. The company looked at and rejected the test house option, internal test equipment and technical construction files. Instead Seaward Electronic started to address the knowledge and expertise problem. After consulting the country's leading EMC experts the company commissioned a successful feasibility study from York University's Electronics Centre, who were eventually briefed to develop the expert system into a commercial product. The resulting system, the Seaward Expert Consultant, offers knowledge and information to companies looking to establish a clear route to EMC compliance. Expert Consultant contains details of all the standards, the relevant test methods, the test procedures and levels of performance. It allows users to enter product details and, by answering yes/no questions, to identify appropriate standards and necessary tests. The Expert Consultant can produce all the necessary documentation to carry out testing and, where appropriate, produce pro forma construction files, which can be completed, stored in the equipment and printed out. It also has a diagnostic capability in the event of problems     

The CEO problem [multiterminal source coding]

We consider a new problem in multiterminal source coding motivated by the following decentralized communication/estimation task. A firm's Chief Executive Officer (CEO) is interested in the data sequence {X(t)} _t=1^∞ which cannot be observed directly, perhaps because it represents tactical decisions by a competing firm. The CEO deploys a team of L agents who observe independently corrupted versions of {X(t)}_t=1^∞. Because {X(t)} is only one among many pressing matters to which the CEO must attend, the combined data rate at which the agents may communicate information about their observations to the CEO is limited to, say, R bits per second. If the agents were permitted to confer and pool their data, then in the limit as L→∞ they usually would be able to smooth out their independent observation noises entirely. Then they could use their R bits per second to provide the CEO with a representation of {X(t)} with fidelity D(R), where D(·) is the distortion-rate function of {X(t)}. In particular, with such data pooling D can be made arbitrarily small if R exceeds the entropy rate H of {X(t)}. Suppose, however, that the agents are not permitted to convene, Agent i having to send data based solely on his own noisy observations {Y_i(t)}. We show that then there does not exist a finite value of R for which even infinitely many agents can make D arbitrarily small. Furthermore, in this isolated-agents case we determine the asymptotic behavior of the minimal error frequency in the limit as L and then R tend to infinity     

The cocktail party problem [instrumentation notes]

Consider a cocktail party with many people attending and many conversations going on simultaneously. If we recorded the sound from somewhere in the room, we would find that we had recorded many conversations at once, and it would be very difficult to tell what was being said by any given person. The problem of taking such a recording, or several such recordings, and separating out the different speakers is known as the cocktail party problem. The generalization of this problem to separating different independent components of a signal without making use of any specific knowledge of the component signals is known as blind source separation. The ability to take a recording in which many people are speaking and to create separate tracks that contain what was said by each person is of great interest to industry and government.     

电子信息类产品3C认证的EMC测试(上)

详细介绍电子产品电磁兼容认证标准及相应的测量方法     

Measurements column [antenna testing]

The alignment of the mechanical axes of a compact range test positioner to the compact range wavefront is addressed. Reflection measurements are used to calibrate the range and to determine the gain of antennas. It is shown that the circular flat plate and the vertical wire are accurate electrical alignment tools for the field direction and the polarization vector. With the plate, it was possible to align the field horizontally and in the horizontal plane within 4 arc s. The polarization vector could be aligned within 7 arc s. Furthermore, the plate can be used to make an error estimate of the center section of the quiet zone, over a wide angular range, and can be used as a gain standard     

Testing comes in from the cold [EMC anechoiuc chambers]

The author describes how small, fully anechoic chambers can be constructed at a fraction of the cost of traditional EMC facilities, and still provide an acceptable route to full-compliance testing for most equipment     

Creative destruction [car crash testing]

Crashing cars-lots of them-is how Volvo safety engineer Daniel Hedqvist earns his living. Running cars into steel barriers or other cars or the sides of mountains is his job. These days the Swede rigging up plenty of Fords for crash tests. Ford owns the prestigious Volvo, Jaguar, and Aston Martin car companies, and has made Sweden its center of excellence for vehicle safety testing. There's a good reason why the second-largest US car maker has ceded this area of expertise to a non-US supplier: few auto companies have won as many awards for car safety as Volvo. This article discusses safety testing of cars at Volvo using virtual crashes and real crashes. The unique features of the test facilities are briefly outlined including the two intersecting test tracks: a 154-meter fixed track and an 80-meter movable one that can be turned as much as 90 degrees. Front and side collisions can thus be tested at virtually all angles. If the back door at the end of the movable track is opened, cars can be sent flying directly into the rocky hillside outside. For so-called barrier tests, a single car on the fixed track hurtles into an 850-ton block at the far end.     

An inspector calls [nondestructive testing]

Composite laminate structures offer many advantages compared with their conventional metal counterparts, but defects can be much harder to detect. In this paper, the author describes how neural networks provide the key to a new, intelligent technique for nondestructive testing     

In-circuit test fixture [PCB testing]

Deficiencies in the conventional in-circuit fixture are presented. A novel fixture is described, and quantitative comparisons are presented. Crosstalk is decreased by 60 dB, and transmission-line matching is possible     

电磁兼容测试场地性能及影响要素

0前言 电波暗室是电磁兼容测试的环境和场地.电磁兼容测试场地大致分为开阔场(open site),半电波暗室(semi-anechoic chamber)和全电波暗室(fully-anechoic chamber).早期的电磁兼容测试是在开阔场中进行的.随着社会的发展,电磁环境日益复杂,人类活动范围扩展,很难找到符合要求的开阔场,于是开阔场的替代场--半电波暗室就应运而生了.但是由于存在地面反射,半电波暗室中的理论计算十分复杂,而且往往测试数据和理论计算也有较大的差距.于是人们又寻求更接近自由空间测试条件,随着吸波材料技术的发展,全电波暗室出现了,暗室6面都装有吸波材料,模拟自由空间,克服了半电波暗室的一些缺点.     

T-star-V型全自动便携式电磁环境测试系统

随着无线电通信事业的迅速发展,无线电设台用户的增加,无线电频率资源日趋紧张,审批台站前无线电通信系统间的电磁兼容分析工作日趋重要.