Mark E. Parker

Exploring the low frequency performance of thermal converters using circuit models and a digitally synthesized source

Low-frequency errors of thermal voltage converters are described and estimated using a circuit model that includes easily measured parameters. A digitally synthesized source is used to confirm the estimated ac-dc differences in the 0.01 Hz to 40 Hz range.

Low voltage standards in the 10 Hz to 1 MHz range

A step down procedure is described for establishing voltage standards in the 1 mV to 100 mV range at frequencies between 10 Hz and 1 MHz. The step down employs low voltage thermal voltage converters and micropotentiometers. Techniques are given for measuring input impedance and calculating loading errors.

A high-accuracy 10 Hz-1 MHz automatic AC voltage calibration system

An automatic system for calibrating high-accuracy ac voltmeters and calibrators is described. The system is based on traditional coaxial, thermal voltage converters to provide ac voltage measurement uncertainties of 5–20 ppm in the audiofrequency range and 5–250 ppm over the full range from 10 Hz to 1 MHz at voltages between 0.5–600 V. Lower levels (0.01–0.5 V) are realized using wideband inductive dividers. Specialized hardware and measurement techniques make it possible to achieve these uncertainties in test periods of approximately 1 min. Random errors introduced by the measurement system are typically less than 2 ppm (one standard deviation).

Internet-based test service for multifunction calibrators

A new method of providing traceability for multifunction calibrators (sources used to calibrate digital multimeters) is described. The method requires a transportable digital multimeter that links a reference calibrator to the calibrator under test and an Internet connection to share test procedures, software, and data. Digital cameras and microphones at both ends enhance communication for troubleshooting and collaboration.

Low-frequency characteristics of thin-film multijunction thermal voltage converters

Low-frequency errors of thin-film multijunction thermal voltage converters are estimated using a simple model based on easily measured parameters. The model predictions are verified by measuring the converters frequency characteristic using a digitally synthesized source.

Programmable digitally synthesized source for low-frequency calibrations

A digitally synthesized source (DSS) designed to calibrate low-frequency (0.1 Hz to 1 kHz) digital voltmeters and thermal converters is described. The DSS output voltage, frequency, and waveform are programmable over the General Purpose Interface Bus (GPIB). The rms value of the output voltage is calculated, with an uncertainty of less than 5 ppm, by measuring the dc voltage of each of the steps used to create the waveform.<<ETX>>

Low frequency characteristics of thermal voltage converters

Low frequency errors of thin-film multijunction thermal voltage converters are estimated using a simple model based on easily measured parameters. The model predictions are verified by measuring the converters frequency characteristic using a digitally synthesized source.