Barry D. Inglis

Bio: Barry D. Inglis is an academic researcher from Commonwealth Scientific and Industrial Research Organisation. The author has contributed to research in topics: Thermoelectric effect & Harmonics. The author has an hindex of 8, co-authored 10 publications receiving 214 citations.

Measuring thermoelectric effects in thermal converters with a fast reversed DC

Abstract: The AC-DC transfer differences of thermal converters due to thermoelectric effects in the heater circuit are directly measured with a fast reversed DC to an uncertainty of a few parts in 10/sup 7/. This new and independent method allows former theoretical methods for evaluating thermoelectric effects in thermal converters to be checked. >

A Method for the Determination of AC-DC Transfer Errors in Thermoelements

Abstract: A method is presented for the determination of ac-dc transfer error as a function of current in thermoelements. To test the method the transfer error variation has been determined for two 10 mA thermoelements at an ac excitation frequency of 57 Hz, and the results compared. On the basis of one of these determinations a dual multijunction thermal converter has been calibrated to provide a check. A number of single junction thermoelements have also been calibrated, and results indicate significantly larger errors as I ? 0 than expected on theoretical grounds. Also, for all thermoelements with Evanohm heaters, the error variation follows a square law of opposite sign to that predicted by theory. An explanation is offered for this behavior. Results indicate that changes in transfer error with current level can be determined to ~1 ppm. Absolute transfer errors for the thermoelements tested however, are probably not known to better than a few ppm.

Frequency Dependence of Electrode Surface Effects in Parallel-Plate Capacitors

Abstract: Electrode surface effects in parallel-plate capacitors lead to a variation in capacitance and conductance with frequency. A method is presented for the determination of absolute changes in capacitance and absolute values of conductance, as functions of frequency. The method involves the use of two variable parallel-plate capacitors, and requires the measurement of relative capacitance and conductance values over a range of frequencies and at a minimum of two different electrode spacings. A capacitor cell, incorporating two variable capacitor sections is described. The cell is designed for use in the investigation of the frequency characteristics of a range of electrode surfaces. Two current transformer ratio-arm bridges are used to perform the relative admittance measurements. The bridges are compensated for capacitance loading, and together cover the frequency range 11 Hz-52 kHz. Measurement precision is a few parts in 108 for each admittance component. Details of the bridges and measurement techniques are discussed and corrections for mechanical resonance effects and lead impedances are considered. Results are given for rhodium plated and plain brass electrodes under vacuum. Over the full frequency range the fractional capacitance change for rhodium, when referred to a 1-mm electrode spacing, is <4 × 10-7. Tan ? is < 1.5 × 10-7. Oil films and organic contaminants on electrode surfaces are thought to be the most likely sources of frequency dependence.

High-frequency AC-DC differences of NML single-junction thermal voltage converters

Abstract: Frequency-dependent AC-DC transfer differences of a new set of single-junction thermal converters that serve at NML as primary standards for AC-DC transfer have been determined. The new determination has led to a reduction of the standard measurement uncertainty from 30 /spl mu/V/V to less than 10 /spl mu/V/V at frequencies up to 1 MHz.

Current-Independent AC-DC Transfer Errors in Single-Junction Thermal Converters

Abstract: AC-DC transfer errors in single-junction thermal converters (TC's) at midfrequencies, and the effect of thermoelectric nonuniformities in their heaters, are discussed. Details of special TC's designed to eliminate or minimize the heater nonuniformities are given. AC-DC transfer measurements have been carried out, relative to a reference pair of converters, on 14 special TC's made to 5 different designs, by 4 different manufacturers. Current-independent ac-dc difference components are determined for each of the TC's from a weighted least squares fit of data taken over a range of currents. Theoretical values of current-independent errors are also calculated, using thermoelectric and thermal conductance data determined from measurements performed on the special TC's or similar units, and applied as corrections to the measured values. The weighted mean of the corrected current-independent ac-dc differences for the group gives an estimate of the current-independent error of the reference pair, and is believed to have an uncertainty of <0.5 ppm. AC-DC transfer measurements, relative to the mean of the group, indicate that two multijunction thermal converters (MJTC's) have current-independent errors exceeding 2 ppm. The current-independent error determined for the reference TC's is to be used in conjunction with a new current-dependent error determination to improve the accuracy of Australia's national ac-dc transfer standard.

Standards for AC-DC Transfer

Abstract: Ac-dc transfer standards provide an essential link for the determination of ac electric quantities in terms of the SI units. Thermal converters are by far the most widely used form of primary ac-dc transfer standards. The basic principles of ac-dc transfer measurements are presented together with background to the performance and basic limitations of thermal converters as transfer standards. Developments in basic converters, voltage transfer standards and current transfer standards are reviewed, with emphasis on developments since 1985. Current activities and possible future directions are discussed.

Measuring thermoelectric effects in thermal converters with a fast reversed DC

Abstract: The AC-DC transfer differences of thermal converters due to thermoelectric effects in the heater circuit are directly measured with a fast reversed DC to an uncertainty of a few parts in 10/sup 7/. This new and independent method allows former theoretical methods for evaluating thermoelectric effects in thermal converters to be checked. >

Design, Modeling, and Verification of High-Performance AC–DC Current Shunts From Inexpensive Components

Abstract: A new type of AC current shunt for AC-DC current transfer is presented for which the AC-DC current differences at frequencies from 10 to 100 kHz are calculated with uncertainties smaller than plusmn 9 muA/A in the current range of 30 mA-10 A. This is an independent realization of the AC-DC current-transfer standards in addition to the step-up method used at most National Metrology Institutes. The construction, modeling, and experimental verification of the shunts are described.

Development of thin-film multijunction thermal converters at PTB/IPHT

Abstract: The thin-film multijunction thermal converter (PMJTC) developed in cooperation between Physikalisch-Technische Bundesanstalt (PTB) and Institut fur Physikalische Hochtechnologie e.V. (IPHT) is today's most sensitive and accurate standard for the precise measurement of electrical AC quantities in the frequency range of 10 Hz-1 MHz. Thin-film technology and micromechanics in silicon were essential for this success. The thin-film heater and bismuth/antimony thermocouples with high Seebeck effect deposited on a thin membrane of low heat conductance result in the attractively high sensitivity of the PMJTC which allows voltage measurements down to 100 mV to be performed. The statistics of the mass production of the PMJTCs show that PMJTCs built into a housing with an N-connector at the input can be reproducebly manufactured with an AC-DC voltage transfer difference smaller than 0.1 /spl mu/V/V at 1 kHz, 8 /spl mu/V/V up to 100 kHz, and below 40 /spl mu/V/V up to 1 MHz for a heater resistance of 90 /spl Omega/. A compensation circuit has been added on the chip which results in low-frequency PMJTCs (LF-PMJTCs) with AC-DC transfer differences below 0.3 /spl mu/V/V at 10 Hz.

AC-DC transfer difference of the PTB multijunction thermal converter in the frequency range from 10 Hz to 100 kHz

Abstract: The ac-dc transfer difference of the multijunction thermal converter (MJTC) developed at Physikalisch-Technische Bundesanstalt (PTB) has been evaluated for various heater resistances between 27 and 700 Ω. By optimizing the heater resistance for voltage transfer to 190 Ω and for current transfer to 27 Ω, transfer differences of a few parts in 107 are achieved up to 100 kHz. Transfer differences caused by thermoelectric effects could be shown to be smaller than 10−8, due to the nearly ideal periodic structure of the converter and the special construction of the intermediate leads between heater and vacuum throughleads. An increase of the transfer difference at low frequencies is caused partly by the change in the real part of the heater impedance, which can be compensated by adding series or parallel resistors to the heater. Another part is found to be a current transfer difference which can only be diminished to a few parts in 107 by increasing the number of thermocouples or decreasing the input power.