摘要:

The purpose of the paper is to review the current status of testing as it relates to printed circuit boards (PCBS) that contain digital LSI and VLSI devices such as a microprocessor. The paper tackles four main subjects: major problems caused by the use of complex devices on PCBSs; techniques for testing specific devices; general-purpose test strategy for PCBs containing complex devices; guidelines and design strategy for testable designs. The paper references 108 other publications available in the open literature.

DOI:10.1049/ip-a-1.1981.0073

出版商:IEE    

年代:1981

数据来源: IET

摘要:

A network method for the solution of general electromagnetic field problems has been introduced in a previous publication. The method was shown to give plausible results but no experimental evidence was given. The present paper describes the methods used for the solution of the circuit equations and a comprehensive set of measurements are presented which demonstrate the validity of the method. Some advantages and drawbacks of the method are also discussed.

DOI:10.1049/ip-a-1.1981.0074

出版商:IEE    

年代:1981

数据来源: IET

摘要:

The methods of torque assessment described in the paper were developed in the course of a programme for increasing the sensitivity of a particular type of clip-round moving-iron instrument. The principal method exploits the relation between inductance change and torque, and so avoids the necessity for constructing precise bearings during the innovating programme. Measurements to simulate the effect of the earth's field are also presented and conclusions are reached concerning the limitations of sensitivity of this type of instrument.

DOI:10.1049/ip-a-1.1981.0075

出版商:IEE    

年代:1981

数据来源: IET

摘要:

In the standard specifications of AC dielectric-characteristic measurements of insulating materials, the test voltage is prescribed as approximately sinusoidal. However, a limit is given for the highest deviation of the HV waveform from the correct sinusoidal shape in terms of a ± 5% tolerance range of the crest factor value respect to the sinusoidal waveform. In the paper, the errors in solid dielectric losses, evaluated at industrial frequencies, due to an applied voltage distorted by a 3rd-harmonic are studied. The analysis is carried out by comparing the dielectric losses in the distorted steady-state with those occurring under the sinusoidal steady state on the basis of the same peak value or of the same RMS value of voltages, thus establishing a reference with the usual methods adopted in measuring test voltage as required by the HV test technique. Curves are obtained showing the errors made in dielectric-loss evaluation as function of 3rd-harmonic content in relation to the 3rd-harmonic phase angle. It is emphasised that crest factor does not completely account for errors in power-loss evaluation. The theoretical results are then shown to be in very good agreement with the experimental data obtained in testing some solid dielectric materials.

DOI:10.1049/ip-a-1.1981.0076

出版商:IEE    

年代:1981

数据来源: IET

摘要:

Despite the abundance of published information on the variation of resonant frequency with temperature of AT-cut quartz crystals, no work has been reported on the temperature variation of the equivalent-circuit elements. Measurements of the change in motional capacitance with temperature are reported in the paper. Results showed that motional capacitance increased linearly over the temperature range – 10 to 70°C. This increase was nearly three orders of magnitude greater than the change in crystal resonant frequency. Clearly, a corresponding decrease in motional inductance must occur to yield the observed frequency/temperature behaviour of AT-cut crystals. The apparent change in angle of cut which occurs with capacitive loading of a crystal was found to be a direct consequence of the large temperature coefficient of motional capacitance. Using this information it is now possible to calculate the apparent angle of cut for various load factors, and to predict the temperature behaviour of crystal oscillators more precisely.

DOI:10.1049/ip-a-1.1981.0077

出版商:IEE    

年代:1981

数据来源: IET

摘要:

The paper illustrates the contribution which behavioural science can make to the formulation of policy in engineering education. ‘Screening’ is the technique which brings together the philosophy and sociology of education with the psychology of learning in the evaluation of significant aims and objectives. The academic versus practical argument, which has led to many policy decisions, as for example the tripartite system of secondary education and the colleges of advanced technology is screened. It is concluded from a historical analysis that the maintenance of the academic versus practical distinction between courses serves only to preserve status diferentials between institutions and their courses. The idea that there are well defined practical and academic abilities is not supported by psychological evidence. If anything, the spatial ability required for engineering design is also required for the pursuit of mathematics. The school syllabus does little to foster the abilities required for technology. The picture is further complicated by the fact that the personality attributes required for high academic performance may not be those required for successful performance either as a manager or entrepreneur. A case for a diversity of courses in engineering subjects has to be made on grounds other than on simple notions about academic and practical abilities.

DOI:10.1049/ip-a-1.1981.0078

出版商:IEE    

年代:1981

数据来源: IET

摘要:

A survey has been conducted of the electronics industry for the purpose of determining the relative importance of quality and reliability in comparisons between the UK industry and its foreign competitors. Data relating to the structure of the industry were also collected. The analysis shows that quality related matters rank high among the milieu of management issues. It is suggested that the quality-assurance function in the smaller specialised firms that constitute so large a part of the industry merits special attention.

DOI:10.1049/ip-a-1.1981.0079

出版商:IEE    

年代:1981

数据来源: IET