Ac Bridge Research Articles

A decoupling calculation method of separating temperature component from the nano-scale metal film thickness measurement output by the eddy current sensor

The eddy current method has been widely applied in the field of nano-scale metal film thickness detection. The output signal of an eddy current sensor is generally tiny in practice, and it is easily affected by the ambient temperature variation, which results in a decrease in the measurement accuracy. How to separate the temperature effect on film thickness measurement for achieving a high precision is a major problem. Therefore, a coupling model of an eddy current sensor with an electromagnetic field and a temperature field is established in this study, and the influence of the film thickness and temperature on coil impedance is calculated. It is found that the inductance and resistance of the coil vary monotonically as thickness and temperature with a measure of linearity in a certain range, as well as the real part and imaginary part of the output voltage by using an AC bridge. Then a film thickness-temperature decoupling calculation method is proposed, and a group of linear calibration intervals are further divided considering the linearity and measurement accuracy. According to the calculation results, it is confirmed that the method can decouple the two, and accomplish a higher accuracy. In addition, the method is verified by a series of experiments, and the variation trend of real and imaginary parts of output voltage with thickness and temperature is consistent with simulation results. At the same time, it is feasible to realize a synchronous detection of metal film thickness and ambient temperature in a certain range.

AC bridge pressure sensor with temperature compensation for high temperature and pressure composite environment

AC bridge pressure sensor with temperature compensation for high temperature and pressure composite environment

The effect of electrical parameters of eddy current sensor on metal film thickness measurement performance and the optimization method.

Eddy current sensors have been widely used in the field of micro- and nano-measurements. The detection circuit is a key part of eddy current sensors. In particular, the electrical parameters in the signal conversion circuit have an important effect on the measurement performance. It is necessary to study the effect of the electrical parameters on the measurement performance and propose an optimization method. In this study, a simulation model of the eddy current sensor is established by coupling a magnetic field and a circuit field. The circuits include the LC parallel resonance, the AC bridge, and three combination circuits of the LC resonant and AC bridge. The output voltage variation with the thickness of copper film is calculated, and the effect of the electrical parameters on sensitivity Ki is obtained. In the LC parallel resonant circuit, it' is revealed that K1 is maximum when the parallel capacitance CP is equal to the resonant capacitance C0. An optimization method of adjusting resistance RS in different thickness intervals is proposed. In the AC bridge circuit, it' is revealed that there exists an optimal RS, which makes K2 maximum. In three combination circuits, K3, K4, and K5 are the maximum when the capacitances (C1, C2, and C3) reach the resonant capacitance C0. In addition, the sensitivity of each combination circuit is improved compared with that of the AC bridge. The relevant analysis results are further verified by a series of experiments. According to the calculation results and the experimental analysis, the optimization method for electrical parameters is further proposed.

INVESTIGATING THE MEASUREMENT ERRORS OF THE COMPONENTS OF THE COMPLEX RESISTANCE OF MUTUAL INDUCTION BY THE PHASE METHOD

A microcontroller measurer of the complex resistance components of mutual induction (MI) of magnetically coupled coils is considered for the case when, due to the effects of “capacitance” and “eddy currents”, an active component arises in the EMF of the secondary coil, the 90° phase shift angle between this electromotive force and the current of the primary coil is violated (“phase defect”). At the same time, corrective terms ("admixture" and "frequency correction") appear in the resistance MI. These phenomena increase with an increase in the frequency and value of the supply current of the coils, when using ferromagnetic cores. Balanced AC bridges are used in well-known resistance component MI measurers; their disadvantages are listed. The developed measurer uses the phase method using a temporary separation of the measurement channel. The measuring circuit (MC) is powered by the current of a controlled generator of sinusoidal signals. In the MC, the measured parameters are converted into the phase shift angle between the two output voltages. These voltages are supplied to the analog inputs of a programmable microcontroller (MCC), in which angle is measured by the discrete counting method. During the measurement process, the MCC sets the frequency of the MC power generator, controls the position of the electronic switch of the measurement channel, measures angle and determines the values of the components of the MI complex resistance according to the specified algorithms. A method of theoretical investigation of measurement errors has been developed. The errors are caused by the inaccuracy and instability of the parameters of the MC and MCC elements appearing in the algorithms for determining the measured values. The method of error calculation is accompanied by a numerical example. The results of calculation of measurement errors are presented.

ACS selects 4 new institutions to join the ACS Bridge Program

The American Chemical Society Bridge Program is an effort to increase the number of chemical science PhDs awarded to students from underrepresented racial groups. This effort is achieved by providing students opportunities to attend transitional programs and partnering with chemical science departments that have demonstrated a strong commitment to supporting students of underrepresented races. This year, ACS is excited to announce that four new partner departments will join the ACS Bridge Program, making for a total of 44 chemical science departments that have participated since the program began in 2018. Congratulations to the new ACS Bridge partner departments for 2022: Florida International University Department of Chemistry and Biochemistry University at Buffalo Department of Chemistry University of North Carolina at Chapel Hill Department of Chemistry University of Virginia Department of Chemistry If your department is interested in becoming an ACS Bridge partner, visit the ACS Bridge Program website at bit.ly/3fgZLRK .

ACS selects 4 new institutions to join the ACS Bridge Program

ACS selects 4 new institutions to join the ACS Bridge Program

An MMC-Based Temperature Control System for a Long-Term Data Collection

We developed a two-stage temperature control system for a long-term stable measurement of AMoRE neutrinoless double beta decay experiment using a dilution refrigerator. The first-stage control was made with a standard PID system using an AC bridge with a ruthenium oxide thermometer as the main thermometer of the mixing chamber plate. The second-stage control was obtained with a magnetic microcalorimeter (MMC) that is configured as a sensitive thermometer for a detector tower, the main experiment. Under single-stage temperature control on the temperature of the mixing chamber plate only with the RuO2 thermometer, the MMC recorded temperature stability of the detector plate of 9 μK rms over 100 min. Under two-stage temperature control, with the first-stage of the mixing chamber plate at 11 mK via the RuO2 thermometer and the second-stage of the detector plate at 12 mK via the MMC, the MMC recorded a temperature stability of 0.5 μK rms over 100 min. Moreover, the heat channels of the AMoRE experiment obtained considerable improvement in energy resolutions when switching from single-stage (RuO2) to two-stage (RuO2 + MMC) control.

Scenes from the ACS Fall 2022 hybrid meeting in Chicago

MEETINGS Scenes from the ACS Fall 2022 hybrid meeting in Chicago ShareShare onFacebookTwitterWechatLinked InRedditEmail Dorea I. ReeserC&EN, 2022, 100 (32), p 46September 12, 2022Cite this:C&EN 100, 32, 46ACS's Kids Zone provided families an opportunity to learn through hands-on activities at Chicago's Navy Pier. (Credit: James Remington/EPNAC.com)Figure1of15ACS immediate past president H. N. Cheng (from left), ACS president Angela K. Wilson, and ACS president-elect Judith C. Giordan (Credit: James Remington/EPNAC.com)Figure1of15Candidate for ACS president Rigoberto Hernandez and Zaida Morales-Martínez at the Donor Reception (Credit: James Remington/EPNAC.com)Figure2of15Author and attorney Hannibal B. Johnson (center) was the main speaker during the ACS Board of Directors regular meeting where he participated in a Q&A with ACS Board of Directors chair Paul Jagodzinski and VP of the Office of Diversity, Equity, Inclusion, and Respect Rajendrani Mukhopadhyay. (Credit: James Remington/EPNAC.com)Figure3of15At the ACS DEIR Reception Honoring AISES's 45th Anniversary, ACS CEO Tom Connelly shakes hands with Sarah EchoHawk, CEO of the American Indian Science and Engineering Society, after signing the chemistry enterprise agreement between ACS and AISES as partner organizations that support one another in advancing chemistry and other STEM disciplines. Pictured standing to the left is ACS president Angela K. Wilson, and ACS Board of Directors chair Paul W. Jagodzinski stands to the right. (Credit: James Remington/EPNAC.com)Figure4of15Laura Gagliardi of the University of Chicago delivered the Fred Kavli Innovations in Chemistry Lecture, titled “Quantum Leaps: Chemistry and Creativity in a Changing World.” (Credit: James Remington/EPNAC.com)Figure5of15Susan Ainsworth, ACS director of donor communications, Office of Philanthropy (left); ACS Bridge fellow Javier Sanlley Hernandez; ACS Scholar Jayda Jackson; ACS donor Sharon Haynie; and ACS CEO Tom Connelly at the Donor Reception (Credit: James Remington/EPNAC.com)Figure6of15ACS Younger Chemists Committee chair Katherine Johnson (left); ACS Nashville Local Section treasurer Jennifer McKenzie; Candidate for ACS President, Mary Carroll, who was on stage in her capacity as ACS Eastern New York Local Section Councilor; ACS Eastern New York Local Section Councilor Warren Hull; ACS Philadelphia Local Section chair Ivona Sasimovich; ACS Eastern US Younger Chemists Committee and ACS Virginia Younger Chemists Committee member Ashley Tubbs; and ACS president Angela K. Wilson at the ChemLuminary Awards ceremony (Credit: James Remington/EPNAC.com)Figure7of15Ellen Matson of the University of Rochester presented the Kavli Foundation Emerging Leader in Chemistry Lecture, titled “Atomic Insights for a Sustainable Future: Understanding Bonding at Metal Oxide Surfaces Relevant to Energy Storage and Conversion Processes.” (Credit: James Remington/EPNAC.com)Figure8of15ACS Board of Directors member-at-large Dorothy Phillips chats with a student presenting a poster during Sci-Mix. (Credit: James Remington/EPNAC.com)Figure9of15Meeting goers pose in front of the popular "Proud to Be a Chemist" sign. (Credit: James Remington/EPNAC.com)Figure10of15Attendees presenting posters at Sci-Mix (Credit: James Remington/EPNAC.com)Figure11of15Meeting attendee Clemens Anklin wearing a science-themed suit (Credit: James Remington/EPNAC.com)Figure12of15At C&EN's Talented 12 reception (from left to right): Bethany Halford, C&EN Senior Correspondent; Pam Poulin, Thermo Fisher Scientific; Jon Balderstone, Thermo Fisher Scientific; Roxanne Kieltyka, T12 Class of 2018; Josep Cornella, T12 Class of 2020; Derya Baran, T12 Class of 2021; Bibiana Campos-Seijo, C&EN Editor in Chief; Alaaeddin Alsbaiee, T12 Class of 2021; Maher El-Kady, T12 Class of 2022; Marcelo Prado, Thermo Fisher Scientific; Connor Coley, T12 Class of 2018; Helen Tran, T12 Class of 2022; Frank Leibfarth, T12 Class of 2019; Gabe Gomes, T12 Class of 2022 (Credit: James Remington/EPNAC.com)Figure13of15Attendees riding the escalator to get to meeting sessions (Credit: James Remington/EPNAC.com)Figure14of15Scenes from the ACS Fall 2022 hybrid meeting in Chicago.

OPTIMIZATION OF BALANCING IN A BRIDGE MEASURING CIRCUIT WITH A DIFFERENTIAL CONDUCTOMETRIC SENSOR

The article is devoted to solving the problem of the occurrence of an additive error in determining local changes in the electrical conductivity of electrolyte solutions under conditions of changes in the background electrical conductivity of the measurement medium, which often occurs in biosensor and other systems with a differential pair of conductometric transducers, if their electrical parameters are not identical. The goal is to provide a deep suppression of the influence of background changes with significant differences in both reactance and active resistance in the transducers of a pair of sensor. The essence of the issue, the causes and mechanism of this type of error, as well as the methods and means of its reduction, developed earlier, are briefly considered. A diagram and description of the structure of a differential conductometric channel of a biosensor system based on an AC bridge, an algorithm for its balancing operations by controlling the module and phase of the test voltage, as well as a vector diagram of currents and voltages in the bridge circuit during this process. The balancing of the bridge has been was modeled analytically, bringing it to a quasi-equilibrium state, in which changes in the background electrical conductivity do not change its output signal. Additional operations for balancing the bridge are determined to achieve such a state with significant differences in both capacitances and active resistances in the impedances of a pair of conductometric transducers of a differential sensor. The results of experimental studies of the suppression of the influence of changes in the background electrical conductivity of a solution in a differential conductometric channel with using its computer model and experimental sample of a conductometric instrument with an electrical equivalent of a differential sensor are presented. A comparison of the results obtained and the corresponding data for balancing bridge circuits by previously developed methods is given. References 16, figures 3, tables 3.

ACS congratulates NSF Graduate Research Fellowship awardees

The American Chemical Society extends its congratulations to three recent US National Science Foundation (NSF) Graduate Research Fellowship awardees who were previously involved with the ACS Bridge Project or the ACS Scholars Program—initiatives that provide support for students from groups underrepresented in the chemical sciences. The three awardees are Esteban Bautista at the University of California, Irvine, Stephanie Oliveras Santos at the University of Wisconsin–Madison, and Kala Youngblood at the University of North Carolina at Greensboro. Since 1952, NSF has awarded over 50,000 Graduate Research Fellowships to students from a pool of more than 500,000 applicants. Forty-two of these fellows have become Nobel laureates and more than 450 have joined the National Academy of Sciences.

Call for applications for ACS Bridge Project Travel and Professional Development Award

The American Chemical Society is inviting applications for the ACS Bridge Project Travel and Professional Development Award, which provides support to underrepresented students to attend an ACS national meeting and/or another online career and professional development event of the recipient’s choice. The award will cover the registration, travel, and lodging costs for attendance at an ACS national meeting and/or fees of another online workshop, course, or virtual event. There are two categories for this award: undergraduate students and graduate students. Both categories are open to students from groups traditionally underrepresented in the chemical sciences. These include Black, Latinx, and Indigenous students. Applicants must be US citizens. Students can apply at cenm.ag/bridgetravel . All applications require a letter of recommendation from the student’s mentor. Applications for this award are accepted on a rolling basis, however those interested in applying to attend the ACS Fall 2022 national meeting must apply by July

Call for applications for ACS Bridge Project Travel and Professional Development Award

Call for applications for ACS Bridge Project Travel and Professional Development Award

Apply to be an ACS Bridge fellow

Apply to be an ACS Bridge fellow

Apply to be an ACS Bridge fellow

Apply to be an ACS Bridge fellow

Third-order Electrical Conductivity of the Charge-ordered Organic Salt α-(BEDT-TTF)2I3

We performed third-order electrical conductivity measurements on the organic conductor $\alpha$-(BEDT-TTF)$_2$I$_3$ using an ac bridge technique sensitive to nonlinear signals. Third-order conductance $G_3$ is clearly observed even at low electric fields, and interestingly, $G_3$ is critically enhanced above the charge-order transition temperature $T_{\rm CO}=136$~K. The observed frequency dependence of $G_3$ is incompatible with a percolation model, in which a Joule heating in a random resistor network is relevant to the nonlinear conduction. We instead argue the nonlinearity of the relaxation time according to a phenomenological model on the mobility in materials with large dielectric constants, and find that the third-order conductance $G_3$ corresponds to the third-order electric susceptibility $\chi_3$. Since the nonlinear susceptibility is known as a probe for higher-order multipole ordering, the present observation of the divergent behavior of $G_3$ above $T_{\rm CO}$ reveals an underlying quadrupole instability at the charge-order transition of the organic system.

Battery absorbs heat during charging uncovered by ultra-sensitive thermometry

The reversible heat in lithium-ion batteries (LIBs) due to entropy change is fundamentally important for understanding the chemical reactions in LIBs and developing proper thermal management strategies. However, the direct measurements of reversible heat are challenging due to the limited temperature resolution of applied thermometry. In this work, by developing an ultra-sensitive thermometry with a differential AC bridge using two thermistors, the noise-equivalent temperature resolution we achieve (±10 μK) is several orders of magnitude higher than previous thermometry applied on LIBs. We directly observe reversible heat absorption of a LIR2032 coin cell during charging with negligible irreversible heat generation and a linear relation between heat generations and currents. The cell entropy changes determined from the reversible heat provide the first verification of the approach of temperature dependent open circuit voltage. Moreover, it is found that the large reversible entropy change can cancel out the irreversible entropy generation at a charging rate as large as C/3.7 and produce a zero-heat-dissipation battery during charging. Our work significantly contributes to fundamental understanding of the entropy changes and heat generations of the chemical reactions in LIBs, and reveals that reversible heat absorption can be an effective way to cool LIBs during charging. Ultra-sensitive thermometry with temperature resolution of 10 μK reveals that batteries absorb heat reversibly during charging. • An ultra-sensitive thermometry with a noise-equivalent resolution of 10 μK. • Observing reversible heat of batteries with negligible irreversible heat generation. • Entropy changes from reversible heat match with that from open circuit voltage. • Batteries generate zero heat with a charging rate of C/3.7

Temperature Coefficient Reduction of AC-Bridge Circuit for Cryogenic Temperature Control System

Precise temperature control is crucial for the development of sensitive instruments, as temperature fluctuations will introduce many negative effects. In temperature control systems, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1/{f}$ </tex-math></inline-formula> noise is dominant in the low-frequency range, which limits the temperature control precision. To suppress the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1/{f}$ </tex-math></inline-formula> noise, AC bridges based on the modulation-demodulation method are commonly used. While the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1/{f}$ </tex-math></inline-formula> noise is suppressed, other types of noise rise to domination, further limiting the precision of the temperature control system. The response of the AC-bridge readout circuit to temperature fluctuation is the most serious. This paper proposes a method for suppressing the response of the AC-bridge readout circuit to temperature fluctuations. Using this method, the temperature coefficient of the readout circuit is reduced by matching the temperature coefficients of the used electro-components according to their weights of impact. This method has been verified in the test of a precise temperature control system designed for a superconducting gravimeter. The temperature coefficient of the AC-bridge circuit was reduced by approximately 57.4 times compared with the unmatched AC-bridge circuit, and the temperature fluctuation in the vacuum chamber of the superconducting gravimeter was controlled within <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\pm 5~\mu \text{K}$ </tex-math></inline-formula> .

The Fundamentals of Building AC Bridges with Phase Regulation

The Fundamentals of Building AC Bridges with Phase Regulation

A temperature measurement system with high resolution and low noise

Due to the temperature fluctuation, both the self-gravity disturbance level of the gravitational wave detection vehicle and the laser interference measurement system are affected, which brings great noise to the gravitational wave measurement, and the temperature field fluctuation has become one of the most important noise sources of the inertial sensor. In order to ensure the noise level of the inertial sensor to meet the needs of detection, this paper uses the AC bridge to reduce the self-noise of the temperature measurement system, improve the resolution of the temperature measurement system, and realize a high-resolution and low-noise temperature measurement system. The experimental results show that the effective value of self-noise of the temperature measurement system is about 3.65 × 10[Formula: see text], and the long-period noise is less than 1 × 10[Formula: see text]. It can be used in the space gravitational wave detection test and control system.

ACS Bridge Program makes an impact

ACS Bridge Program makes an impact