摘要:

A method for accurately measuring the relative d.c. and a.c. sensitivities of d.c./a.c. transfer instruments is described. The method is applied to an electrostatic voltmeter whose transfer error is found to be less than one part in 10000. In the course of the measurements a sensitive method has been developed for investigating harmonic generation in non-linear filters.

DOI:10.1049/pi-2.1954.0100

出版商:IEE    

年代:1954

数据来源: IET

摘要:

A technique is described and standard integral forms are presented for the application of a new performance criterion for servo mechanisms based upon minimizing the time moment of error-squared of a system in response to a given signal. Examples of its use are given, in the course of which a novel graphical method of analysing servo mechanisms is described.The new criterion is a comprehensive one depending upon the complete error transient. It is related to the minimum-integral-of-error-squared criterion, which has been previously proposed. The latter criterion, while convenient for mathematical manipulation, suffers from the severe disadvantage that systems based upon it do not give the best practical results. As a consequence of considerable practical experience with the simpler types of servo mechanism it is usual to express empirically design requirements which lead to systems yielding the best practical results. Any criterion of practical significance should satisfy these requirements in such cases. It is the purpose of the paper to show that the minimum-moment-of-error-squared criterion does satisfy these requirements although the minimum-integral-of-error-squared criterion does not, and to recommend that the time-weighted criterion be adopted for the design of the modern special-purpose system, where the original empirical requirements are not necessarily appropriate.

DOI:10.1049/pi-2.1954.0102

出版商:IEE    

年代:1954

数据来源: IET

摘要:

An experimental investigation was carried out to obtain the behaviour of a position-control system whose amplifier has a non-linear amplitude characteristic classed as the “hard-spring” type. Apart from the non-linearity aspect the system is simple, being a second-order remote-position-control servo mechanism stabilized by a “phase advance” network. Results have been obtained for transient response and steady-state frequency response under various operating conditions. Some theoretical verification is also included.

DOI:10.1049/pi-2.1954.0103

出版商:IEE    

年代:1954

数据来源: IET

摘要:

The size and operational features of modern mercury-arc rectifiers are determined largely by the mercury transfer from the pool cathode, 80–90% of the total valve volume being required to handle the evaporated mercury.1The amount of mass transfer accompanying spot emission is thus of fundamental importance; it is characterized by the amount of mercury removed from the pool per ampere of emission current per second, the accepted value being 5 mg/amp/sec for power rectifiers.2Many attempts to control this mass transfer have failed through the lack of knowledge of the fundamentals of spot emission and their relations with the features which accompany it.The paper describes the development of means (low-heat-resistance anchors) of reproducing the various distinct phases of spot emission, and demonstrates the existence of functional relationships between the specific phase of emission and the accompanying quantities, in particular of mass transfer. It is suggested that the suppression of mass transfer is equivalent to the selection of specific phases of emission, and that this can be achieved by suitable designs of cathode. Finally, the first practical applications of the new principle are described.In view of several references to the performance and peculiarities of the free-spot emission, these are surveyed in the Introduction.

DOI:10.1049/pi-2.1954.0106

出版商:IEE    

年代:1954

数据来源: IET

摘要:

The investigation was carried out to satisfy the need for reliable information on resilient materials used for reducing the transmission of structure-borne noise.Two machines were designed for the dynamic testing of twin samples of material under known compressive loads, and their development and performance are described. Results on typical materials have been obtained over a range of frequencies from 1 cycle in 10 minutes to values in the lower audio register. The lower limiting value of dynamic stiffness has been called the “incremental stiffness,” and the method of measuring it is described. The effects of wave motion in soft rubber have been investigated for two small samples using a high-frequency apparatus; and at certain frequencies, depending on the dimensions of the specimen, the transmitted force for a given oscillatory deformation is shown to be about seven times that at low frequencies. By using simple beam arrangements, measurements of both creep and incremental stiffness have been made on three types of material, over a period of about 1000 hours of continuous loading. Results are presented showing that most creep occurs during the first 100 hours.The techniques described enable useful information on the performance of resilient materials, as used for the reduction of vibration, to be obtained.

DOI:10.1049/pi-2.1954.0109

出版商:IEE    

年代:1954

数据来源: IET

摘要:

The paper describes two methods of employing the relation between the resonant frequency and the dimensions of a resonant cavity to measure small displacements.The principle is applied to the measurement of torque in shafts. Existing methods of measuring torque are discussed.

DOI:10.1049/pi-2.1954.0110

出版商:IEE    

年代:1954

数据来源: IET

摘要:

The paper describes a new method for the non-destructive measurement of the mechanical hardness of ferromagnetic components, based on the relationship between a “coefficient of magnetic hardness” and the variables in the upper portion of the magnetization curve. It is shown that there is a direct relationship between the magnetic permeability and the mechanical hardness of a low-alloy-content steel, and this is used as the basis of a d.c. magnetic method of hardness measurement for two steel components of diverse character. The construction and performance of portable apparatus for the testing of armour-piercing shot and crank-end bushes is described in detail, and the test results obtained are discussed. The reproducibility of readings is better than 1%, almost linear correlation between instrument reading and mechanical hardness is obtained, and the sensitivity is of a reasonable order. The simplicity of operation is such that unskilled personnel may be employed for routine testing.

DOI:10.1049/pi-2.1954.0111

出版商:IEE    

年代:1954

数据来源: IET

摘要:

The theory of the transient behaviour of certain ladder networks, having a finite number of sections, when subjected to a unit-function voltage surge is developed rigorously. The networks chosen are those usually employed to represent a coil or winding in which each section has inductanceL; capacitance to earthCgand capacitance between sectionsCs. Solutions for the transient voltages produced in such a network when the end is open or short-circuited are obtained using the Laplace transform.The solutions are general and show that only certain frequencies are excited in such a network. In particular, the treatment indicates errors in the earlier work of Rudenberg which are important since they lead to inaccuracies concerning the stresses to be expected in a machine or transformer.Calculations show how the important ratioCg/Csaffects the voltage distributions and stresses, and how special cases of engineering importance (transformer, machine, choke, artificial line) can be derived by selecting appropriate values ofCg/Cs.Finally, by allowing the number of sections to become infinite, solutions are obtained for continuous windings and for a transmission line.

DOI:10.1049/pi-2.1954.0114

出版商:IEE    

年代:1954

数据来源: IET

摘要:

Transductors with four-limbed cores have characteristics which differ from those of conventional transductors in their symmetry with respect to control-current changes. Such transductors are suitable for increasing the sensitivity of non-polarized relays and may be operated by either d.c. or a.c. signals.The suppression of response to negative signals is also possible with four-limbed transductors, and this may be used to reduce swamping effects in push-pull magnetic amplifiers subjected to large signal inputs.

DOI:10.1049/pi-2.1954.0115

出版商:IEE    

年代:1954

数据来源: IET

DOI:10.1049/pi-2.1954.0116

出版商:IEE    

年代:1954

数据来源: IET