The authors have between them more than 60 years of experience in making electrical measurements in National Measurement Laboratories. These laboratories are the source of measurement standards and techniques for science and engineering and are dedicated to maintaining the international system of units (SI) by establishing and disseminating the values of measurement standards with the lowest possible uncertainty. Careful attention to detail is required in designing measurement systems that eliminate electrical interference and are as simple and as close to first principles as possible. This book draws on their experience by offering guidance and best practice for designing sensitive electrical measurement circuits.
In particular the book describes examples that demonstrate the elegance, flexibility and utility of balanced-current coaxial networks in obtaining the ultimate in noise-matching and interference elimination for precise and accurate voltage, current and power measurements. It also updates an earlier book on coaxial AC bridges by including recent AC measurements of quantum Hall resistance to establish a primary quantum standard of impedance and by extending impedance measurements in general to higher frequencies.
Lord Kelvin (William Thomson), arguably Britain's most eminent scientist after Newton, spent much of his life in work which led to the development of today's electrical units and standards. Despite his influence, there are few biographies of stature (largely due to the abstruse nature of much of his technical research). This treatment concentrates upon his work in three phases; discovery of the fundamental concepts and coding them into universal laws, leading the adoption of the metric system, and securing worldwide use of units and standards (now the IEC system).
The need to measure electrical power is common to many branches of science and engineering. This book presents a wide-ranging survey of the many types of radio-frequency and microwave power meter and the techniques which are used for calibrating and intercomparing them. The frequency range is 1 MHz to 200 GHz.
The first of the sixteen chapters considers the fundamentals. Four chapters are then devoted to the subject of calorimetry, which forms the basis of the majority of primary standards for power measurement. A further five chapters describe the various types of non-calorimetric power meter, which include not only the commonly used thermistor, thermoelectric and diode types, but also force-operated instruments and a considerable number of miscellaneous devices. Calibration and intercomparison methods are covered in three closely linked chapters which treat respectively the basic techniques, the use of reflectometers for power meter calibration, and the problems associated with connectors and adapters. In the last three chapters a mixture of topics is covered. First a concise survey of pulsed power measurements is presented. Attention is then given to the topics of voltage and current measurement, which are closely related to power measurement. Finally, the subject of the international intercomparison of standards is discussed and the results of some of the more important intercomparison exercises are summarised.