Dan Bee Kim

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.

All-around dual source impedance bridge

Two terminal dual source impedance bridge was configured using commercial voltage calibrators. The bridge performance was evaluated by measuring 1 to 1 resistance ratio at 1 kHz using 1 kΩ and 10 kΩ resistors. The same bridge was used for the resistance (R) to the inductor (L) and the capacitor (C) ratio measurements by adjusting the phase between the voltage sources. Then, the AC resistance value was found from the R : C ratio. This simple two terminal dual source impedance bridge proved its reliable and versatile measurement capability.

Piston guide and magnet assembly for the KRISS watt balance

The piston guide and magnet assembly for the KRISS watt balance were tested. The velocity of the piston guide was controlled within 4×10-3 at the velocity of 2 mm s-1 using a linear motor and linear encoder feedback. The magnet assembly which consists of two permanent magnet rings and closed yokes was fabricated. B-field at the air gap of 25 mm was measured using a Hall probe. The B-field uniformity was within 5×10-4 over the vertical distance of 24 mm.

The effect of humidity on the calibration of air-type capacitance standards

This paper describes our observation of the effect of humidity on a four-terminal-pair (4TP) air capacitance standard set. A standard set (Agilent 16380A) has been monitored four fourteen days at 1 kHz frequency using an AH 2500A capacitance bridge. Consistent increment of measured capacitance was observed for all the capacitors in the set as the humidity increases. In addition, the analysis on the humidity-dependent capacitance reveals that the capacitance value follows the humidity changes with a delay of about 0.7 day.

Uncertainty evaluation using the Monte-Carlo method for the calibration of four terminal pair air capacitance standards

We developed a calibration software based on the Suzuki method for the calibration of a commercial four terminal pair air dielectric capacitance standard. The uncertainty of the calibration has been evaluated using the Monte-Carlo method. The calibration results showed good agreement with those of Keysight technologies.

Calibration of capacitance in the frequency range up to 1 MHz

This paper describes two different ways to calibrate the capacitance in the high frequency range up to 13 MHz. First, a dual source bridge was configured using two voltage sources and then the ratio of two capacitors was measured in the frequency range from 1 kHz to 1 MHz. The second method known as the Z-matrix method, allowed us to measure the capacitance value up to 13 MHz. The measured values were compared with the reference values calibrated by the PTB and Agilent Technologies, respectively, and they were also compared with each other. The cross-checks showed that both methods are reliable to an order of 10-5 at 1 MHz.

Precision ac-dc difference measurements of a thermal transfer standard based on a Josephson sampling voltmeter

Progress in the development of an evaluation system for thermal-transfer standard based on a Josephson waveform synthesizer at KRISS. The synthesizer adopting a Josephson junction array, which can generate arbitrary stepwise waveforms with a number of the quantum-voltage steps up to 2.5-V level amplitude. With the synthesizer, we have built a sampling voltmeter that measures the differential voltages between a sinusoidal waveform produced by a semiconductor-based ac source and the Josephson waveforms. We will present in the conference that the developed sampling voltmeter can be utilized as a reference for ac-dc difference measurements of a thermal transfer standard.

A simple double-balance impedance bridge for routine calibrations

Impedance measurements are wildly required for most of the electrical metrology laboratories. Therefore, it is needed to establish different measurement systems with different levels of accuracy to meet all demands. So, a simple impedance bridge is presented through this paper. It is more suitable for routine calibrations of impedance. Theory of operation, construction, and basic balance equations are demonstrated. To verify this new established impedance system, some of the measurements related to the resistance have been carried out. Therefore, the optimum operating voltage at the commonly used 1 kHz frequency has been specified to the achieved relative error which is in the order of 10-5.