Marian Kampik

Comparison of three accurate methods to measure AC voltage at low frequencies

Three methods for the determination of the RMS value of AC voltage at low frequencies are compared: the step calibration of a digitally synthesized source, the optimized sampling method, and the AC-DC voltage transfer with a multifunction thermal converter. The three methods agree within 1/spl times/10/sup -6/ with an uncertainty of 2.5/spl times/10/sup -6/ in the frequency range from 10 Hz to 100 Hz.

Low-frequency AC-DC voltage transfer standards with new high-sensitivity and low-power-coefficient thin-film multijunction thermal converters

New Planar Multijunction Thermal Converters (PMJTC) with low power coefficient and high dynamic range using CuNi44/BiSbTe-thermocouples were developed. Together with carefully evaluated range resistors for voltages up to 1000 V they resulted in ac-dc transfer standards with negligible ac-dc voltage transfer difference at low frequencies. The measuring system was improved with a new highly stable low frequency voltage source.

High-frequency thin-film multijunction thermal converter on a quartz crystal chip

The design of a new planar or thin-film multijunction thermal converter (PMJTC) on a quartz chip results in improved performance for frequencies higher than 100 kHz due to smaller dielectric losses and higher insulation resistance in the quartz membrane and the quartz chip. The window with the membrane is anisotropically etched into the quartz crystal chip. The temperature of the heater is radiometrically sensed with a thin-film infrared sensor. At frequencies higher than 100 kHz the ac-dc voltage transfer differences are one order smaller than with the standard PMJTC with the Si/sub 3/N/sub 4//SiO/sub 2//Si/sub 3/N/sub 4/ sandwich membrane on a silicon chip.

Experiences With a Two-Terminal-Pair Digital Impedance Bridge

This paper describes the realization of a two-terminal-pair digital impedance bridge and the test measurements performed with it. The bridge, with a very simple architecture, is based on a commercial two-channel digital signal synthesizer and a synchronous detector. The bridge can perform comparisons between the impedances having arbitrary phase and magnitude ratio. The bridge balance is achieved automatically in less than 1 min. R-C comparisons with calibrated standards, at kilohertz frequencies and 100-kQ magnitude level, give ratio errors of the order of 10-6, with potential for further improvements.

A precise two-channel digitally synthesized AC voltage source for impedance metrology

A two-channel AC voltage source based on digital synthesis is reported. We present measurement results of some of the key properties at 1 kHz with applications like digital impedance bridges in mind. Measurements show that amplitude ratio of the channels has a stability (Allan standard deviation) of one part in 108 for a 30 min measurement. The phase difference between the channels is also stable within 0.1 μrad.

A bridge for maintenance of inductance standard

A bridge for maintenance of primary 10 mH inductance standard is described. The bridge simplifies and speeds up the maintenance procedure of group inductance standard and enables also the calibration of an external standard in relation to any member of the group. It can measure directly the inductance and series resistance differences of compared inductors at frequency 1 kHz and at operating current less than 70 mA. The measurement range is within /spl plusmn/10 /spl mu/H and /spl plusmn/200 m/spl Omega/ of the nominal value, the resolution /spl plusmn/1 nH and /spl plusmn/20 /spl mu//spl Omega/, and type A standard uncertainties are smaller than /spl plusmn/2 nH, and /spl plusmn/1 m/spl Omega/, respectively. The inductance measurement uncertainty is approximately 20 times smaller than observed one-year drift of a single standard inductor. The bridge is provided with a serial PC interface, and a manual switch for fast choice of compared inductors. The paper presents the concept of the circuit and measurement procedure, enhancing the result accuracy. The influence of connecting cables and problems with switching of compared inductors are also discussed.

Determination of the AC-DC voltage transfer difference of high-voltage transfer standards at low frequencies

The ac-dc transfer difference at low frequencies of thermal converters for higher voltages with planar multijunction thermal converters (PMJTCs) and series resistors has been determined by using only the established linear change of the low-frequency ac-dc current transfer difference of the PMJTC with input power. Uncertainties of less than 1 muV/V are achieved up to 1000V

High Performance Digitally Synthesized Source for Very Low-Frequency AC Voltage Calibrator

The paper describes a high-performance digitally synthesized source (DSS) designed for low-frequency AC voltage calibrator. The source generates very stable and accurate sinusoidal AC voltage from 1.2 to 12 V in frequency range from a few muHz to 100 kHz.

Analysis of the Effect of DAC Resolution on AC Voltage Generated by Digitally Synthesized Source

This paper presents an analysis of the effect of the digital-to-analog converter resolution on the root-mean-square value of the sinusoidal signal generated by the digitally synthesized source (DSS) of low-frequency standard ac voltage. The analysis applies to the DSS being calibrated using the peak-to-peak method.

Comparison of Nonquantum Methods for Calibration of the Digital Source of Very-Low-Frequency AC Voltage

This paper presents methods of calibration of digital sources of ac voltage of very low frequency (0.001–100 Hz) and of effective value from 0.5 to 5 V. This work deals primarily with the calibration methods of the digital source of the sinusoidal signal [digitally synthesized source (DSS)] which is approximated with the staircase waveform. The construction of the DSS and the calibration system is presented. The calibration methods are divided into dynamic and static. Of the dynamic methods, the thermal method and integrating sampling method are briefly presented. Of the static methods, the step and the peak-to-peak methods of calibration are briefly presented. The potential applications, basic features, and accuracy of all four methods are discussed. This paper also presents a comparison of results obtained using the methods of calibration described in this paper.