Seitaro Kon

Error and Uncertainty Estimations for A Passive-CC-Based AC Current Ratio Standard at High Audio Frequencies

This paper describes a development framework for alternating current ratio standard working at high audio frequencies. To realize this, first, a calibration method for frequency-dependent balancing current generators (BCGs) producing error currents to balance current comparators (CCs) is proposed. Second, the BCG error correction is made not only for the current transformer (CT) calibration but also for the CC self-calibration. Third, practical capacitive error corrections are also proposed to be introduced for the CT and CC calibrations. Finally, in consideration of the BCG error, capacitive error, and compensated CC error, a proposed way of calculating CT error and estimating its uncertainty is described.

Calibration methods of a CC and BCG for a high-accuracy AC current ratio standard up to 4 kHz

This paper describes calibration methods of current comparators (CCs) and balancing current generators (BCGs) accompanied with them, for establishing a high-accuracy ac current ratio standard up to 4 kHz. The CC calibration is explained mathematically according to the self-calibration procedure that NMIJ has been exploiting. The BCG calibration is based on measurement of the conversion ratio. The technique with a CC and CT is unique in terms of the fact that the uncertainty can be ignored against the CT calibration.

Evaluations of a wideband inductive voltage divider and non-sinusoidal power measurement system

This paper describes a non-sinusoidal power measurement system developed by NMIJ. To validate the verification of the system, a wideband IVD and synchronous sampling measurement method were evaluated.

An evaluation method for wideband voltage dividers using two phase-locked signal generators

This paper describes a proposed evaluation method of a wideband voltage divider of wide voltage and ratio ranges. An evaluation system developed to realize the proposed method is introduced. To ensure the validity of the system, the results by the proposed method have been compared with those by a conventional method using standard IVDs. A large departure between them is observed as higher frequencies around 100 kHz.

Improvement of uncertainty analysis for waveguide VNA measurement at terahertz frequency

This paper describes a new measurement uncertainty analysis for scattering parameter measurements of waveguide devices in the frequency range from 750 GHz to 1.1 THz. The measurement uncertainty of Vector Network Analyzer (VNA) has already been analyzed from uncertainty of primary standards and repeatability. However, estimated uncertainties of waveguide VNA measurement over 110 GHz were underestimated in the case of comparison by two measurement systems at terahertz frequency. Other uncertainty contributions are connection torque deviation and effect from IF cables between VNA and frequency extension modules. By using new uncertainty model, results from two systems agreed within the uncertainty.

Expansion of the measurement range of AC shunt resistor standard

There has been a demand for accurate measurements of ac shunt resistors with a nominal value of 1 mS or less for both in-phase and quadrature components. Thus, to expand the ranges of impedance and frequency of the calibration system for ac shunt resistors, a current bridge method with cascaded current transformers (CTs) has been developed. An ac shunt resistor with nominal value of 10 mS was evaluated by a current bridge method using cascaded CTs, and the results of the calibration system using this method were validated. It was found that the calibration system for ac shunt resistors using the current-bridge method with cascaded CTs can be used successfully for both in-phase and quadrature components up to 3 kHz.

Method for automatic compensation of the loading effect for high-precision buffer amplifiers

To reduce errors due to loading effects, an automatic compensation circuit (ACC) for the loading effect is developed. The concept of the ACC is quite simple. The ACC generates a current in relation to the difference between the input and load voltages. The ACC compensates for the errors automatically with only a connection to the buffer amplifier in parallel. The errors due to loading effects were compensated to nearly zero with the ACC. Furthermore, to confirm the function of the ACC, we used an inductive voltage divider (IVD) that has known load characteristics. The errors of the in-phase components reach 1 × 10-4 owing to loading effects, but the errors are compensated to nearly zero with the ACC. Similarly, the errors of the quadrature components are compensated by the ACC automatically.

Effect of current heating on accurate measurements of AC shunt resistors

To propose a structure for high-accuracy shunt resistors, the frequency and current dependencies of AC shunt resistors with different current ratings are evaluated both for AC resistance and phase angle. To evaluate these characteristics, a modified current-bridge method was developed. The AC resistances of the shunts do not vary considerably with the frequency, up to 3 kHz. The phase angle of AC shunts varies proportionally to the frequency. The current dependence of the AC resistance of shunts seems to change with current value. The current dependence of the phase angle of the shunt remain stable up to 10 A.

Evaluation of a magnetic bridge current sensor using standard shunts

In this paper, a magnetic bridge current sensor for power electronics is evaluated using an evaluation system with standard shunts. The transresistances of the sensor were measured and the uncertainties of the system were calculated in the input current range of 1 mA to 100 A.

Evaluation of Atypical-Ratio Wideband Voltage Dividers With Consideration for Impedance Mismatches

This paper proposes a novel method that uses two phase-locked signal generators to evaluate wideband voltage dividers that have wide voltage ratio ranges, including atypical ratios like 1/101. These voltage dividers are intended to be fabricated by applying the Hamon principle. Verification of the proposed method was carried out using standard inductive voltage dividers calibrated using Thompson’s method. In this paper, we also consider impedance mismatch effects on the phase measurements taken during the evaluation.