Designing instrumentation circuitry with rms/dc converters

摘要

Using rms to measure waveforms furnishes thern most accurate amplitude information (Refer-rnence 1). Rectify-and-average schemes, whichrnyou usually calibrate to a sine wave, are accuraternfor only one waveshape, however. Departuresrnfrom this waveshape result in pronounced errors. Although accurate, rms conversion often entails limited bandwidth, restricted range, complexity, and difficult-to-character-ize dynamic and static errors. Recent developments address these issues and also improve accuracy. Table 1 at the Web version of this article at www.edn.com/ms4228 shows Linear Technology's LTC1966/LTC1967/LTC1968 device family. The devices feature low-frequency accuracy, including linearity and gain error, of 0.5% and 1% error at band-widths extending to 500 kHz. These converters employ a sig-ma-delta-based computational scheme to achieve their performance.