Planar Multijunction Thermal Converters Research Articles

Signal-to-Noise Ratio Optimization for Planar Multijunction Thermal Converters

We investigate a comprehensive design guideline for optimizing the signal-to-noise ratio (SNR) of planar multijunction thermal converters (MJTCs). Optimizing the leg-length of the thermocouple using a shunted copper patch facilitates an increase in the sensitivity to more than twice that of a conventional thermocouple when the device fulfills the thermal impedance matching condition. The SNR does not depend on the thermocouple number or the leg cross-section at a fixed total cross-sectional area. Finally, during thermocouple material selection, different combinations of three thermophysical parameters, the Seebeck coefficient, electrical resistivity, and thermal conductivity, that provide the same figure of merit would lead to different values of the SNR. For improving the SNR, increasing the Seebeck coefficient is the most desirable approach. The reduction of thermal conductivity is desirable for short leg-lengths, whereas increasing the electrical resistivity is better for long leg-lengths. The findings provide a useful guide to design optimal planar MJTCs by maximizing the SNR.

The AC amplitude and channel characterization of high-resolution digitizers

High-resolution (24-bit) ADC based sampling devices e.g. NI PXI 5922 and NI PXI 4461 are usually used for precise electric power measurement purpose so it is required to characterize them in a proper way. According to that, several measurement techniques are proposed to characterize ac amplitude and channel characteristics at the maximum frequency of up to 100 kHz. An automated test and calibration system based on a planar multijunction thermal voltage converter and a modular electronic instrumentation platform has been developed. Furthermore, two ADCs, i.e. NI PXI 5922 and NI PXI 4461 have been compared with reference standard (Swerlein algorithm) to investigate their precision in RMS amplitude measurement of ac signals. In addition, this paper presents the PXI digitizers’ channel characterization in both sinusoidal and non-sinusoidal regime as the main contribution which results in comprehensive insight into digitizers’ performances and their mutual comparison. Accordingly, relevant uncertainty analysis is presented as well.

Planar Multijunction Thermal Converters With Increased Sensitivity Operated in Hermetically Sealed Housings Filled With Noble Gas

The sensitivity of planar multijunction thermal converters was significantly increased by filling the housing with noble gasses, preferably xenon or krypton. The performance was observed for almost two years, and no degradation of the sensitivity was found. Also, the frequency response of the ac–dc transfer difference remains unchanged at high frequencies and even improves below 40 Hz. Using the lowest at present manufacturable heater resistance of 90 $\Omega $ with the noble gas filling, ac–dc transfer at voltages down to almost 70 mV compared to about 100 mV in air becomes possible.

Final report: EURAMET.EM-S39

The AC-DC difference of a set of current shunts produced by the Norwegian Metrology Service (Justervesenet), were measured by PTB and Justervesenet, in a bilateral comparison, where Justervesenet acted as the organizer and pilot laboratory. The nominal values of the current shunts are 30 mA, 100 mA, 300 mA, 1 A, 3 A, 5 A, 10 A and 20 A, which were measured at their nominal values for the frequencies 10 Hz, 20 Hz, 55 Hz, 110 Hz, 400 Hz, 1 kHz, 5 kHz, 10 kHz, 20 kHz, 50 kHz and 100 kHz. All current shunts were measured in combination with Planar Multi-junction Thermal Converters produced by PTB.The results show that there is a degree of equivalence within 0.4 for all measured values, and that for frequencies below 10 kHz, the value is typically below 0.2. Hence, there is a very close agreement between the measurements, which are not correlated by traceability chains, and the properties of the current shunts have been documented by the comparison. Main text.To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/.The final report has been peer-reviewed and approved for publication by the CCEM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

A thermal approach to waveform–independent energy determination

In this paper, a new device for power and rms value measurement is presented. Unlike the commercially available measurement equipment, this device is not limited to special waveforms. As a reaction to the increasing use of energy harvesters, which gather energy from the ambience to power low-power electronics, it is necessary to develop new measurement equipment that is not limited to sinusoidal signals (harvesters generally deliver nonsinusoidal signals). Therefore, a new device is presented based on an isothermal operating mode of a planar multijunction thermal converter (PMJTC). Unlike previous PMJTCs, this one is equipped with an additional gold heater and is operated by a regulating circuit, which is electrically isolated from the input. The output signal of the regulator is recorded and analyzed to determine the power and rms value of the input signal.

Realization and Validation of the 10 mA-100 A Current Standard at CEM

Centro Español de Metrología (CEM) has developed a new ac-dc current standard to improve our measurement capabilities and extend the measurement range to 100 A and 100 kHz. The new standard is based on a step-up procedure using the combination of specially designed shunts and planar multijunction thermal converters. The new CEM ac-dc standard, the validation method, the uncertainty estimation, and the results are described.

Real power measurement using a thermal converter

In this paper, a new application of thermal converters is presented which allows energy, power and rms measurement without the need to substitute the measurement signal with a dc signal as performed in ac–dc transfer. Using a mathematical model of standard planar multijunction thermal converters (PMJTCs), the effective power acting inside the heater of the PMJTC is calculated from the output signal of its thermocouples. Due to the underlying physical principles, this method not only allows the calculation of the rms value of sinusoidal signals but also the average power and absolute energy contained in non-sinusoidal, non-periodic and even non-stationary signals, as appearing in the characterization of energy harvesters.

Low-Frequency Characterization in Thermal Converters Using AC-Programmable Josephson Voltage Standard System

We have measured the low-frequency characteristics of thermal voltage converters down to 1 Hz using a differential sampling measurement system based on ac-programmable Josephson voltage standard (AC-PJVS) system. The measured ac-dc transfer difference of a planar multijunction thermal converter using our system is evaluated to be <; 1 μV/V above 10 Hz and <; 35 μV/V at 1 Hz with lower uncertainties compared to the conventional method. The estimated overall uncertainty measured by using our system is 3.1 μV/V ( <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">k</i> = 1) at the frequency of 10 Hz and root-mean-square voltage of 3 V. Our measurement results above 10 Hz are in good agreement with the results obtained by the conventional method within a standard deviation of the mean. Our differential sampling measurement system using AC-PJVS is a useful tool for low-frequency ac voltage metrology.

Reconfigurable Unit for Precise RMS Measurements

A system for the precise measurement of electrical quantities by means of the root-mean-square (RMS) value of ac voltages or currents is described. The system is based on a planar multijunction thermal converter (PMJTC) and low-cost electronic components. The miniboard circuitry can also be used in several experiments where flexibility is required. As a first application, the system can carry out ac voltage comparisons and ac or dc voltage measurements. The system is designed to operate with a single PMJTC sensor in the range where its sensibility is greater. This paper shows the possibility of employing the PMJTC sensors outside the laboratory environment. The performance of the unit has been characterized, and measurements of ac signal RMS values in the audio band (below 1.5 V) show stability better than 3 muV/V.

Improved High-Input-Impedance mV-Amplifiers With Gain Factors From 10 to 900

New millivolt-amplifiers (mV-amplifiers) driving planar multijunction thermal converters (PMJTCs) at their output have been developed to measure the output voltage of micropotentiometers (mupots). Using a twin-stage design with gains of 10, 20, and 30 per stage, total gain factors ranging from 10 to 900 are achieved. This results in a usable range of input voltages from 100 muV up to 100 mV at frequencies ranging from dc to 1 MHz. A novel offset compensation results in small reversal differences, and this allows for reliable operation at higher gain factors. There is a sophisticated protection circuit to avoid damage of the PMJTC in the case of overload. The ac-dc transfer difference is flat within 100 muV/V up to 100 kHz.

Calibration of AC-DC Current Transfer Standards from 10 mA to 100 A Using a Step-Up Procedure

Recent developments have resulted in new planar multijunction thermal converters fabricated on quartz substrates, which are now used as primary calculable ac-dc current transfer standards with very...

Explanation for the AC–DC Voltage Transfer Differences in Thin-Film Multijunction Thermal Converters on Silicon Chips at High Frequencies

In this paper, an explanation for the ac-dc voltage transfer differences at frequencies greater than 100 kHz of the standard thin-film or planar multijunction thermal converter (PMJTC) developed at the Physikalisch-Technische Bundesanstalt and fabricated on a silicon chip has been found. The simulation indicates that the capacitance of the bond pads of the heater is the reason for an increase of the ac-dc voltage transfer difference of PMJTCs with higher heater resistance to negative values. Bond pads of smaller size and larger distance are shown to improve the frequency response

Quartz Thin-Film Multijunction Thermal Converters With Built-In Tee Connector for 100 MHz

Planar multijunction thermal converters (PMJTC) on quartz crystal chips and membranes have been fabricated. Compared to previous single-junction thermal converters, these devices exhibit calculable and smaller ac-dc voltage transfer differences in the frequency range from 1 MHz to 100 MHz along with a 3- to 10-fold reduction in uncertainty. Built-in Tee connectors are used to avoid the contribution of leads and connectors to the ac-dc voltage transfer difference of the PMJTC chip. The contribution of different designs of built-in Tees to the overall uncertainty of the calculable standard has been evaluated. The uncertainty budgets are discussed in detail

New Generation of Crystal Quartz Thin-Film Multijunction Thermal Converters

The design of a new generation of planar multijunction thermal converters (PMJTCs) on quartz membranes and on quartz crystal chips improves the frequency response of the PMJTC in the frequency range from 100 kHz to 100 MHz and allows a decrease in the uncertainties. For a heater resistance of 1 kOmega ac-dc voltage transfer differences smaller than 5 muV/V are calculated for frequencies above 100 kHz up to 1 MHz. This is a reduction of more than one order of magnitude in the ac-dc voltage transfer differences for such high heater resistance in comparison to the PMJTCs with Si3N4/SiO2/Si3N4 sandwich membrane on a silicon chip. The quartz PMJTCs allow the improvement of the standard uncertainties to 3 muV/V in the frequency range of 100-500 kHz and 5 muV/V for 700 kHz to 1 MHz. The model for calculating the ac-dc voltage transfer differences and the uncertainty budget are given

Fabrication of Low-Frequency AC-DC Thermal Converter with Thermal Mass

The use of a thin film or a planar multijunction thermal converter (PMJTC) for the ac-dc transfer of voltage and current is well established. In general, a three dimensional multijunction thermal converter (MJTC) has the advantage of accuracy and a single junction thermal converter (SJTC) has that of low cost. PMJTCs provide a long-term stability, a high sensitivity and a high-dynamic-frequency range. It is well known that PMJTCs show small ac-dc voltage transfer differences in the audiofrequency range. However, it is difficult to obtain a small ac-dc transfer difference at low frequencies, particularly with thin-film-based thermal converters. The small ac-dc transfer difference at low frequencies is caused by nonlinearities in the heat transport mechanism (in thin films) and in the thermal-to-electric conversion process (in the thermocouples of thin films). This study has been conducteded to achieve a smaller ac-dc transfer difference on thin-film chromel-alumel thermal converters operating at low frequencies. An optional silicon obelisk is formed underneath the thin membrane to minimize ac-dc transfer differences at lower frequencies. The floating obelisk structure enhances the isothermal operation and slows thermal transfer compared with the standard configuration without the obelisk, resulting in a smaller ac-dc transfer difference at low frequencies. Also, it is possible that thin-film thermal converters can be used as the flow sensor and infrared sensor.

Determination of the AC–DC Voltage Transfer Difference of High-Voltage Transfer Standards at Low Frequencies

The low-frequency AC-DC voltage transfer differences of thermal converters for higher voltages with planar multijunction thermal converters (PMJTCs) and series resistors have been determined by using only the assumption of a linear change of the low-frequency AC-DC current transfer difference of the PMJTC with input power. Uncertainties of less than 1 /spl mu/V/V are achieved up to 1000 V.

Synthesis of Precision Waveforms Using a SINIS Josephson Junction Array

A synthesizer of precision ac waveforms based on a binary superconductor insulator-normal metal-insulator-superconductor (SINIS) Josephson junction array has been developed. The array segments are individually biased using a high-speed bias source which gives a switching time of approximately 250 ns between voltage steps. The accuracy limitations of the system due to limited risetime and bandwidth are discussed. Comparisons between the synthesizer and a planar multijunction thermal converter (PMJTC) indicate that it is possible to synthesize sine waves with known rms value having an accuracy in the range of 1 part in 10/sup 7/.

Millivolt Calibrations Using Micropotentiometers With New Disc Resistors and Planar MJTCS Aided by New Millivolt Amplifiers

New micropotentiometers (/spl mu/pots) have been built with planar multijunction thermal converters (PMJTC) on Si- and SiO/sub 2/-substrates, and with new disc resistors and redesigned housings. The step down from 100 mV to 2 mV can be performed with only two /spl mu/pots. New millivolt-amplifiers with gain factors of 11, 50, and 121 in conjunction with PMJTCs are developed to measure the output voltage of the /spl mu/pots down to 2 mV. Their high input impedance of >1 M/spl Omega/ /spl par/ < 6 pF avoids the loading of the output resistor of the /spl mu/pots. These systems lead to considerable reduction of the uncertainties in the millivolt-AC-DC transfer in the frequency range from 10 Hz up to 1 MHz.

Quartz Planar Multijunction Thermal Converter as a New AC–DC Current Transfer Standard Up to 1 MHz

The new generation of PMJTCs on quartz membranes and on quartz crystal chips developed at the PTB results in new ac-dc current transfer standards for the current of 10 mA and the frequency range from 10 kHz to 1 MHz, accompanied with small uncertainties. For a PMJTC with a heater resistance of 240 Omega the uncertainties for frequencies up to 100 kHz are smaller than 1 muA/A and up to 1 MHz they increase to 5 muA/A (k=1). A model for the PMJTC has been developed which allows calculating the ac-dc current transfer difference as well as the attributed uncertainties. The agreement of the simulation and the measurement were tested for high heater resistances of 700 Omega and 240 Omega, for which quite large ac-dc differences are calculated. The good agreement validates the model

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 (PMJTCs) with low-power coefficient and high dynamic range using CuNi44/BiSbTe thermocouples have been manufactured. In series connection with carefully evaluated range resistors for voltages up to 1000 V they result in AC-DC voltage transfer standards with known AC-DC voltage transfer difference at low frequencies, for which the voltage step-up procedure is not necessary any more.