Recent Advances in Precision AC Measurements

Development of a new monolithic thermal sensor, a unique high-impedance attenuator, a precision sample-and-hold circuit, and a novel ac-error-correction technique have brought significant improvements in the accuracy of ac measurements. A precision thermal truerms measurement system is described that offers a transfer stability of 25 parts/106 in the frequency band 40 Hz-kHz. A microprocessor-based system uses a nonvolatile memory for software calibration; this enhances dc, ac, and resistance measurement accuracy, including production and repair.