The RF voltage measurement capability of an equivalenttime sampling system has been investigated over the frequency range of 1-100 MHx. The system is easily calibrated from step response measurements, independent of thermal transfer standards. Comparison measurements made with NBS-calibrated thermal converters show agreement generally within the stated uncertainties presently provided by NBS for such calibrations. The system offers several advantages over conventional thermal transfer techniques: acldc transfers are not required, loading and transmission line problems are reduced, and direct measurement of voltages from 2 V to as low as 10 mV are possible. In addition, other waveform characteristics are readily obtained, e.g., average and peak values, harmonic distortion, etc.
A theoretical and practical framework is presented to aid in the design, fabrication, and testing of transformer-like devices for use in high-accuracy ac current metering applications. Current transformers, two-stage current transformers, and current comparators are discussed, as well as related devices that use passive and active error correction techniques. Transformer theory is developed in terms of simple electromagnetic theory and practical equivalent circuits. Magnetic design equations are presented and the measurement of relevant magnetic properties is discussed. Sources of error and their mitigation are covered in detail, including errors caused by magnetizing currents, winding and core inhomogenieties (so-called magnetic errors), and circulating capacitive currents. Calibration methods and current transformer testing are also covered.
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