The bulk modulus loss factor of small, relatively loss-free solid specimens is one of the more elusive elastic constants to measure, as it is essential that the losses in the apparatus be reduced below those in the sample. A procedure described by Tamm in 1942. involves the insertion of the sample at a pressure maximum in a column of liquid resonating in a longitudinal mode; the loss factor was determined from the change in damping of this resonance. Essentially the same procedure was followed by Niemic in 1972, who reports a Q of 1300 as typical for the resonator without a sample. Simon in 1965 attempted to eliminate viscous loss in the boundary layer at the tube wall by the use of purely radial modes in spherical vessels such as have commonly been used for the measurement of the attenuation in liquids. He suspended the flask in a vacuum jacket to reduce radiation loading, and used a common transducer at the centre for the initial drive and the measurement of decay. He obtained a Q of over 20000, though the excitation of wall resonances and the asymmetry at the neck caused considerable difficulty. The present method makes use of a cylindrical vessel in order to produce a more practical system.

No description available.

possible transfer device for the precise measurement or standardization of an alternating current with reference to a precisely known direct current. A full method of operation has been developed and an experimental and theoretical consideration of the various sources of error carried out. The performance has been compared with that of existing a.c. - d.c. transfer devices, and it is shown that the indirectly heated thermistor is a valuable addition to this field, particularly in the measurement of very low frequencies. The actual idea of using the indirectly heated thermistor as a transfer device is not original, nor is the measurement of the thermistor characteristics themselves (section 2.5). It is believed, however, that all the work concerning the actual bridge design and operation, the analysis of its performance, and the investigation of the sources of error is original, and that, as a result of this work, this device can be confidently used for measurements of the highest precision. During the course of this investigation, comparison measurements were carried out between the indirectly heated thermistor and the vacuo-thermo-junction. Discrepancies which appeared in these measurements were ultimately attributed to limitations in the existing theory of transfer errors in vacuo-thermo-junctions, concerning the effects of Thomson and Peltier heating. This theory has been reconsidered and a new generalized theory developed which is shown to be applicable also to the indirectly heated thermistor. It is evident, that providing certain precautions are taken in the construction, the vacuo-thermo-junction is capable of the highest precision. It is believed that the new 3. theory and the supporting analysis is largely original. Some of the work on the indirectly heated thermistor has been published by the author in the Proceedings of the Institution of Electrical Engineers, Vol. 103, Part B, November, 1956.

The work presented here investigates proposals for a new generation LCR component meter which takes advantage of advancing technology through the environment of Virtual-Instrumentation, itself a relatively new concept. The new instrument, based jointly upon time and frequency domain analysis, employs a Phase-Sensitive-Detector and the Discrete-Fourier-Transform as a pair of complimentary detectors to realise a single and multi-frequency testing strategy. The unknown component is excited with either a single sine-wave or broadband signal comprised of a number of harmonically related sinusoids. An object-oriented software design was used to implement a graphical-user-interface for the control of the instrument and results obtained from it.

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This thesis discusses the design of an instrument that will measure Total Harmonic Distortion (T.H.D.) over the range 20 hertz to 100 kilohertz and which has completely automatic frequency tuning over the entire frequency range. The first chapter outlines the categories of instruments available to perform signal analysis and introduces the topic of T.H.D. Chapter 2 is a review of the essential theory necessary for an understanding of active filters, including the subject of network sensitivity. Chapters 3 to 6 deal with the circuitry used to attenuate the fundamental frequency component by the required amount. Chapter 3 is a comparison of the different types of frequency rejection or notch filters, and Chapters 4 and 5 discuss alternative methods of tuning the filter parameters and how automatic filter tuning may be obtained. Chapter 6 details how the remaining attenuation is achieved in a stage following the notch filter. The circuitry used to amplify the harmonic components to a suitable level for measurement and the display circuitry are discussed in Chapter 7, and Chapter 8 deals with amplitude and frequency range selection. The noise performance of the instrument is considered in Chapter 9, and in Chapter 10 the practical considerations and performance of the prototype instrument are given.

This thesis discusses the principles and design of an experimental impedance calculating electronic component meter based on time domain signal analysis. The design of the measuring circuit and ranging system is based on the use of a direct, floating-point dual slope conversion process. Accuracy is maintained over the entire impedance measurement range although low converter clock rates are used. Experimental PSD techniques are described and discussed. A highly modular instrument software package is presented, orientated to the requirements of the development environment. The instrument design uses relatively little analogue circuitry and much of the signal processing is performed by one device.