Two-stage Inductive Voltage Divider Research Articles

Comparison of a 100-pF Capacitor With a 12 906-Ω Resistor Using a Digital Impedance Bridge.

We tested a digital impedance bridge in a hybrid structure for comparison of a capacitor with a resistor where the impedance ratio was measured in two separate parts. The modulus of the impedance ratio was matched arbitrarily close to the input-to-output ratio, in magnitude, of a two-stage inductive voltage divider by adjusting the operating frequency of the bridge; the residual deviation between the two together with the phase factor of the impedance ratio was measured using a custom detection system based on a four-channel 24-bit digitizer. The ratio of the inductive voltage divider was calibrated, in situ, using a conventional four-arm bridge with two known capacitors. Fluctuations of the source voltages were largely removed through postprocessing of the digitized data, and the measurement results were limited by the digitizer error. We have achieved an overall bridge resolution and stability of 0.02 μF/F in 2 h for measuring a 100-pF capacitor relative to a 12 906-Ω resistor at 1233 Hz. The relative combined standard uncertainty (k = 1) is 0.13 μF/F, dominated by the digitizer error.

Two-Stage Coaxial Inductive Voltage Divider and Its Calibration Setup for Use Between 1 and 100 kHz

This paper describes the development of a compact n/8 inductive voltage divider (IVD) for the use in the frequency range between 1 and 100 kHz and voltages up to 5 V. The development includes a number of additional inductive components for the bootstrap calibration setup such as a supply transformer which ensures the galvanic isolation of the calibration setup, a calibration transformer, and a detection transformer. The desired frequency and uncertainty range requires a two-stage IVD design with coaxial windings, a triaxial differential branch, and voltage controlled shields to minimize capacitive stray currents. The bootstrap calibration setup follows a special coaxial-by-design scheme, which guarantees nearly identical currents in inner and outer conductors of the coaxial connections without use of any chokes. The calibration of the IVD yielded in-phase and quadrature IVD corrections within $6 \cdot {10}^{-6}$ and $1 \cdot {10}^{-6}$ both with uncertainties ( $k=2$ ) below 1 $\cdot {10}^{-6}$ at 100 kHz.

Design and Calibration of Inductive Current Transformer

In this paper, the design principle of inductive current transformer is introduced at first. Then an inductive current transformer is produced by applying the structure of two-stage inductive voltage divider. And finally, the error of the sample machine is given through examine test, and the suggestion for improving the machine is given based on the data. The data from the sample machine shows that: without compensation winding, the error level of 1200 ampere-turn of inductive current transformer can reach 0.1 level, after adding the compensation winding, it can reach 0.02 level. The design and data have laid a foundation for the future design of inductive current transformer with higher level of accuracy.

A Two-Stage, Guarded Inductive Voltage Divider with Small Ratio Errors for Coaxial Bridge Applications

The traceability chain to derive the capacitance unit from the quantum Hall resistance comprises some coaxial bridges. These bridges employ a main two-stage inductive voltage divider to provide the voltage ratio needed. One such divider has been recently constructed and calibrated at Inmetro. The design techniques responsible for the small ratio errors of the device and the calibration method employed are both detailed. The new divider was installed in Inmetro's two terminal-pair coaxial capacitance bridge with significant improvements in the bridge resolution and accuracy.

Two-stage Inductive Voltage Divider using Special Winding Method

Inductive voltage dividers (IVDs) are widely used in the field of AC measurements, such as impedance measurements at audio frequencies. Two-stage guarded IVD has been developed by D N. Homan and T L. Zapf about forty years ago. However, it is not easy to construct the two-stage guarded IVD. Therefore, we have developed a two-stage IVD using special winding method without guard by magnetic and electrical shield. To reduce admittances of each winding wires, corrugated cardboard of polypropylene is used for new two-stage IVD. In addition, ratio winding and excitation winding were wound toroidally around two FINEMET ring cores using PEW flat cable 0.7 mm in diameter. As a result, the in-phase ratio errors are within ±6.1×10-8 of the input at frequency 1kHz or less. In this report, the winding methods and measurement results of new two-stage IVD are described.

AC QHE-based calibration of resistance standards

A coaxial transformer bridge for QHE-based calibration of resistance standards has been developed. An eight-decade two-stage inductive voltage divider forms ratio arms of the bridge and triple-series connection of the reference QHE sample to the bridge is employed. Frequency characteristics of LEP heterostructures have been measured by comparing them against resistors with calculable frequency dependences. Two quadrifilar, Gibbings's type resistors with nominal values of 12 906 /spl Omega/ and 6353 /spl Omega/ have been used in this measurement.

A Measurement Transformer for Establishing Accurate Voltage Division in Thermal Converter Measurements up to 1000 V and 100 kHZ

A self-calibrating measurement transformer for use in a new step-up method to determine the ac/dc transfer errors of thermal converters is described. The transformer is a two-stage inductive voltage divider incorporating a screened secondary, and is designed so that the decade sections have almost ideal symmetry. The voltages of the decade sections can be determined with uncertainties of a few parts × 10-6 at 1000 V and 100 kHz, and with much smaller uncertainties at lower frequencies.