True-rms-to-dc converters, such as Model 440 and 441, have excellent bandwidth, accuracy, and crest-factor capability; however, their inputs are single-ended, with input impedance, typically 8.5kΩ. For use in test-equipment design, a differential-measurement capability was necessary to avoid ground-loop problems; also, it was desired that the measuring leads lightly load the circuit under test. Read full article
