Analog Interface Research Articles

Design Analysis and Human Tests of Foil-Based Wheezing Monitoring System for Asthma Detection

We present a flexible acoustic sensor that has been designed to detect wheezing (a common symptom of asthma) while attached to the chest of a human. We adopted a parallel-plate capacitive structure using air as the dielectric material. The pressure (acoustic) waves from wheezing vibrate the top diaphragm of the structure, thereby changing the output capacitance. The sensor is designed in such a way that it resonates in the frequency range of wheezing (100–1000 Hz), which presents twofold benefits. The resonance results in large deflection of the diaphragm that eradicates the need for using signal amplifiers (used in microphones). Second, the design itself acts as a low-pass filter to reduce the effect of background noise, which mostly lies in the >1000-Hz frequency range. The resulting analog interface is minimal, and thus consumes less power and occupies less space. The sensor is made up of low-cost sustainable materials (aluminum foil) that greatly reduce the cost and complexity of manufacturing processes. A robust wheezing detection (matched filter) algorithm is used to identify different types of wheezing sounds among the noisy signals originating from the chest that lie in the same frequency range as wheezing. The sensor is connected to a smartphone via Bluetooth, enabling signal processing and further integration into digital medical electronic systems based on the Internet of Things (IoT). Bending, cyclic pressure, heat, and sweat tests are performed on the sensor to evaluate its performance in simulated real-life harsh conditions.

Simulation of the analogue interface for remote measurements

This work is aimed at finding possibilities for increasing the accuracy of measurements and interfering analog interfaces for remote measurements using resistive strain gauges by introducing a new structural scheme, which is shown on the Fig. 1. It shows us the Schematic of the electrical functional analog interface for remote measurement using multiplexer and resistive strain gauges, which contains a measuring chain, a transmitter, the input of which is connected to a DC source through an analog demultiplexer, and the outputs of the measuring chain through the analog multiplexer are connected to the measuring amplifier, and a two-channel analog-digital converter with simultaneous sampling. The measuring chain is made in the form of three resistive current dividers, where one divider is formed by a resistive strain gauge and adjusting resistor, and two others – exemplary resistors.By introducing a new structural scheme, it will be possible to increase the accuracy of measurements and impedance of analog interfaces for remote measurements using resistive strain gauges. In this case, unlike the classical method of model measures, this method is distinguished by the «indistinguishability» of the measuring line, which makes it possible to compensate for a greater number of influential factors, in particular, the correlated noise of operational amplifiers and noise caused by the presence of the overall ground loop, the resistance of analogue switches and lines of communication.At the Fig. 2 we can see the electric model of the measuring channel in the software Elektronic Workbench.From the analysis of the simulation results it was found that the random additive component of the error would dominate. Since in the simulation of the only random component of the error there is a quantization error, the use of the differential method of measuring the output voltage will significantly improve the metrological characteristics.

An Analog Interface Circuit for Capacitive Angle Encoder Based on a Capacitance Elimination Array and Synchronous Switch Demodulation Method.

This paper presents an analog interface application-specific integrated circuit (ASIC) for a capacitive angle encoder, which is widely used in control machine systems. The encoder consists of two parts: a sensitive structure and analog readout circuit. To realize miniaturization, low power consumption, and easy integration, an analog interface circuit including a DC capacitance elimination array and switch synchronous demodulation module was designed. The DC capacitance elimination array allows the measurement circuit to achieve a very high capacitance to voltage conversion ratio at a low supply voltage. Further, the switch synchronous demodulation module effectively removes the carrier signal and greatly reduces the sampling rate requirement of the analog-to-digital converter (ADC). The ASIC was designed and fabricated with standard 0.18 µm CMOS processing technology and integrated with the sensitive structure. An experiment was conducted to test and characterize the performance of the proposed analog interface circuit. The encoder measurement results showed a resolution of 0.01°, power consumption of 20 mW, and accuracy over the full absolute range of 0.1°, which indicates the great potential of the encoder for application in control machine systems.

In situ measurement of dental resin-based composite volumetric shrinkage and temperature effects using in-fibre bragg grating methods

ObjectivesResin-based composites (RBCs) are commonly used in dental restorations. It is known that RBCs undergo volumetric shrinkage during photo-polymerization leading to a detrimental increased stress state at the RBC-tooth interface and potentially early restoration failure. The objectives of this in vitro study were: (1) to ascertain whether shrinkage strain could be measured using in-fibre Bragg grating (FBG) technology, without confounding effects of temperature; and (2) to ascertain whether FBGs can detect alteration in shrinkage strain with introduction of a surface condition change at the RBC-cavity analog interface. MethodsAluminum cavity analogs with simulated cavity dimensions 3.5 mm height x 2 mm width x 8 mm length and 2 mm wall thickness were secured in a 3D printed experimental jig. Two FBGs were used in the RBC space, one that was covered with a polyimide tube and that measured only temperature, and another that was affected by both mechanical strain and temperature. Experiments to determine if the two FBG system could be used to compensate for thermal artefacts were contrived to verify that a tube-covered and bare FBG measure the same temperature effect (n = 5). In situ photo-polymerization experiments, which consisted of using controlled amounts of SureFil SDR Flow + RBC, were performed to study RBC shrinkage behavior. As-machined (n = 10) and micro-etched (n = 11) cavity analogs were used. Significant differences in FBG measurements, which could indicate the ability of FBGs to detect alterations in strain across surface preparations, were determined using one tail t-tests at 95% confidence. Finally, additional temperature experiments were conducted 5 h after initial light exposure using the same light irradiation regiment to investigate temperature effects within a cured RBC system (n = 3). ResultsFor temperature measurement, the tubing-covered and bare FBGs measured temperature changes with time-lag of 3.7 ± 1.4 s (tubing-covered FBG relative to bare). For measurements in cured RBC, the bare FBG and tubing-covered FBG measured different strains, with the bare FBG measuring larger apparent strains because this FBG is affected by thermal volumetric expansion of the RBC and a temperature increase of the FBG itself. The tubing covered FBG, that is isolated from volumetric expansion effects, measured relatively less. The interpretation of these results is that thermally-compensated strain measures (in-situ) could require simultaneous use of two FBGs (one strain isolated). In situ measurements of the photo-polymerization procedure for as-machined analogs at two time-points, 500 and 1000 s, were determined to be −485.43 ± 131.06 μstrain and −524.96 ± 134.78 μstrain, respectively. For air-abraded surfaces measures were significantly lower at (p < 0.001) −211.36 ± 12.38 μstrain and −228.07 ± 49.08 μstrain, respectively. ConclusionsTo measure shrinkage strain and compensate for associated thermal effects from photo-polymerization, systems employing two FBGs, one of them isolated from thermal volumetric expansion, may be required. The presented approach proved capable of detecting significant alteration in strain across two surface preparations.

Simulation of the Analogue Interface for Remote Measurements Using Multiplexer and Resistive Strain Gauges

The simulation of the analog interface circuit based on the measuring amplifier with differential inputs and the ultrasonic scheme and algorithm of non — destructive additive — multiplicative correction have been made. Such schematic of the analog interface reduces the influence of input correlated noise of operational amplifiers and network drives on the «general» resistance.&#x0D; The Fig. 1 shows us the Schematic of the electrical functional analog interface for remote measurement using multiplexer and resistive strain gauges, which contains a measuring chain, a transmitter, the input of which is connected to a DC source through an analog demultiplexer, and the outputs of the measuring chain through the analog multiplexer are connected to the measuring amplifier, and a two-channel analog-digital converter with simultaneous sampling. The measuring chain is made in the form of three resistive current dividers, where one divider is formed by a resistive strain gauge and adjusting resistor, and two others — exemplary resistors.&#x0D; At the Fig. 2 we can see the electric model of the measuring channel in the software Elektronic Workbench.&#x0D; From the analysis of the simulation results it was found that the random additive component of the error would dominate. Since in the simulation of the only random component of the error there is a quantization error, the use of the differential method of measuring the output voltage will significantly improve the metrological characteristics.

The Analogue Interface for Remote Measurements Using Multiplexer and Resistive Strain Gauges

An analogue interface circuit that contains a mea­suring chain, a transmitter, the input of which is connected to a DC source through an analog demultiplexer, and the outputs of the measuring chain through the analog multiplexer are connected to the measuring amplifier, and a two-channel analog-digital converter with simultaneous sampling is developed. The measuring chain is made in the form of three resistive current dividers, where one divider is formed by a resistive strain gauge and adjusting resistor, and two others — exemplary resistors. This work is aimed at finding possibilities for increasing the accuracy of measurements and interfering analog interfaces for remote measurements using resistive strain gauges by introducing a new structural scheme, which is shown on the Fig.2.

Development of the system for vibration diagnosis of bearing assemblies using an analog interface

We have proposed a system for early vibration diagnosis of gas-pumping units, specifically bearing assemblies with improved metrological characteristics. The technique makes it possible to solve the task of early diagnosis of roller bearings under adverse conditions of application. The study has shown that this is achieved through the use of tracking notch filters based on N-channel structures using the iterative-integrating converters. The simulation results of the 4-channel filter under actual input signals of bearing damage have demonstrated its effectiveness. Based on this, we have built the resulting model for the filter’s output signal. Here we show a functional circuit for the root-mean-square values detector with a model of the output signal from the tracking notch filter at actual input signals. To build a model of signal at the input to a root-mean-square values detector, we determined filter responses for each frequency, which is responsible for a certain damage. The time of analysis was selected so that it was equal to a period of the minimum beat frequency, that is, Ta=164 ms (for a bearing of type 222). We investigated effectiveness of the device by simulating a damage to an actual gas turbine engine’s bearing. The procedure for analysis has been proposed and the generalized vibro-diagnostic criterion has been suggested, which takes into consideration the degree of engine’s load. This improves accuracy and reliability of preliminary analysis when diagnosing a roller bearing at the stage of the origin of the damage. Characteristics are given for the electrometric measuring amplifier for work with piezoelectric sensors and the proposed charge measuring amplifier to work with piezoelectric sensors. Under condition for the imbalance of the input link, which is due to the non-identity of parasitic capacitances of the input cable. It is shown that the penetration of a network disturbance to the output of the charge measuring amplifier provides for the signal/noise ratio that is two orders of magnitude better than that for the electrometric measuring amplifier.

A CMOS full-range linear integrated interface for differential capacitive sensor readout

This manuscript presents the development of an integrated analog interface able to convert differential capacitive sensors variations into a DC voltage. The presented circuit exploits the architecture developed in previous works of the same authors, based on autobalancing bridge techniques, further improving its performances through the linearization of the input/output characteristic and the achievement of the full-range sensor variations capability. The interface takes advantage of Low Voltage and Low Power integrated circuit design techniques, optimizing performances for flux and force sensor. Simulated results with the AMS 0.35um standard CMOS technology have shown a very good agreement with the theoretical model developed, obtaining an error lower than 2.5% and a total power consumption of 5 mW. Moreover, waiting for the chip production, a discrete element board has been also implemented and tested. Preliminary measurements on the test board have shown satisfactory input/output linearity characteristics with overall reduced percentage error (lower than 1.5%) in the measurand estimation.

Autobalancing Analog Front End for Full-Range Differential Capacitive Sensing

The authors here propose an analog interface for differential capacitance estimation, able to reveal and quantify capacitive variations. Different from other works in the literature, the proposed interface can operate on a full-range scale. This solution takes inspiration from a preliminary work of the same authors, whose working principle is based on a modified De-Sauty AC bridge configuration; in particular, two (differential) capacitors and two resistors are employed, one of which is implemented by a voltage-controlled resistor (VCR). In this paper, the electronic interface has been redesigned to obtain full-range operation and a linear input–output characteristic. The implemented autobalancing mechanism controls the VCR generating a reference voltage following the sensor output. Simulation results in two different circuit configurations performed by OrCAD PSpice have shown a very good agreement with a theoretical model implemented in MATLAB/Simulink environment. In addition, an evaluation of the goodness of the experimental measurements at steady and unsteady conditions is given. Experimental tests on a discrete-component prototype have been carried out using an automated test equipment including National Instruments tools and a dedicated software in the LabVIEW environment. Measurements have shown satisfactory results, the standard deviation being on the order of 0.01, in the worst case. The linearity error has been evaluated as well, resulting in lower than 1% full scale.

End-to-End Analysis of Integration for Thermocouple-Based Sensors Into 3-D ICs

Solutions to the integration challenges of a new thermal sensor technology into 3-D integrated circuits (ICs) will be discussed in this paper. Our proposed architecture uses bimetallic thin-film thermocouples, which are thermally linked to points of measurement throughout the 3-D stack with dedicated vias. These vias will be similar to thermal through-silicon vias (TSVs) in structure, yet different in functionality. We propose a low-overhead design methodology by linking the sensor placement task with the existing thermal TSV planning phase for 3-D ICs. A fraction of thermal TSV resources is decoupled from their original use and repurposed for the temperature sensing infrastructure. Tradeoffs concerning the reduction of the thermal TSV resources are investigated. Furthermore, we present an end-to-end system, including the physical realization of the sensor network as well as its analog interface circuitry with the sensor data sampling unit. We demonstrate the operation and correctness of this interface with transistor-level simulations. Next, through thermal modeling and simulation using a state-of-the-art tool (FloTHERM), we demonstrate that we can achieve high accuracy (1 °C error) in temperature tracking while still maintaining the effectiveness of the thermal TSVs in heat management (conforming to a peak temperature constraint of 95 °C).

Current conveyor-based differential capacitance analog interface for displacement sensing application

A current conveyor-based analog electronic interface for differential capacitive sensors is here shown. The read-out circuit that utilizes second generation Current Conveyors (CCIIs) as active blocks is able to evaluate differential capacitive variations performing a capacitance-to-voltage conversion. This solution has been implemented both in a discrete element board and as integrated version in a standard 350nm CMOS technology. Simulations and experimental resultshave shown a linear input/output characteristic and a good agreement with theoretical expectations, being the former performed for both the designed solutions, whereas the latter only for a discrete prototype board (employing a low cost commercial component (AD844). Sensitivity and resolution data on a practical case-study of a displacement sensor are constant and their values are satisfactory. Both simulated and measured results make the proposed architecture a good candidate as first stage of analog front-ends to be employed in differential capacitive instrumentation.

Improving control engineering education with TRIK cybernetic system

We present our experience in the application of a new cybernetic system, TRIK, for control engineering education at university level. The TRIK system is composed of an embedded controller, analogue and digital input-output interface and an inertial measurement unit which can be easily programmed with visual and text based computer languages. The system can be efficiently used for robotic and control engineering prototyping and education. In the present paper, we describe and discuss various applications of the system in education covering basic control theory problems and advanced robotic system development. Our experience with TRIK has demonstrated that the developed system and corresponding curricula improves the efficiency of control engineering education at university level, and has significant potential to promote science and technology at secondary school level.

Metallic Iron Effects on Coke Analog Carbon Bonding and Reactivity

In this study, characterization of the porosity, carbon bonding, and reactivity of coke analog materials prepared with and without metallic iron has been carried out. The porosity of the analog is well controlled, reproducible, and typical of a metallurgical coke. Using Raman spectroscopy, the coke analog carbon bonding is a combination of sp2 and sp3–sp2 bonding types and the values overlapped with those reported for metallurgical coke. It has been widely reported that metallic iron increases graphitization (increases sp2 bonding) of metallurgical coke. This has been replicated in the coke analog and shown to principally occur at the metallic iron–coke analog interface and not throughout the bulk of the coke analog. The reaction of coke analog containing metallic iron with CO2 has been evaluated using thermogravimetric analysis over the temperature range 1173–1623 K. It has been found that the coke analog containing metallic iron displayed similar, but faster reaction behavior to coke analog with no metallic iron.

CMOS-SOI-MEMS Uncooled Infrared Security Sensor With Integrated Readout

A new generation of uncooled passive infrared (PIR) security sensors based on a suspended thermal transistor MOS (TMOS), fabricated in standard CMOS-SOI process, released by post-etching, and wafer level packaged achieving a vacuum of $\sim 2$ –4 nWatt) due to its subthreshold operation requiring $\sim 10$ nA at 0.2 V, enabling wide range of battery applications. This paper focuses on the analog design of monolithically integrated readout for the electronic system, formed by the PIR sensor, its front-end analog interface and the processing circuitry. The measured signal-to-noise ratio of this system is 100–200, depending on the operation point, at the black-body temperature of 50° C, while the total input referred noise is $\le 1~{\mu }$ Vrms and the total system current consumption is no more than $20~{\mu }\text{A}$ . The sensors and read-out are processed with the same CMOS-SOI technology.

Development of the computerized system for control of curved surfaces with the help of inductive sensors

The article presents the main results of research on the analog interface for remote measurement of linear and angular displacement values inductive sensors with high metrological characteristics. The main purpose of the study is to develop a computerized system for remote measurement and control of curved surfaces using inductive sensors, which provides increased performance and noise immunity. This is achieved by creating a new multifunctional transducers based on iterative integrating converters differentially-current inputs, reduce the effects of stray capacitance electrical cables through the shunting effect is almost zero input resistance and can increase the frequency of the test signal. It is shown that at the same time increases the quality factor of the primary winding IDPTT and reduces the influence of destabilizing factors on the sensitivity of the sensor. The presented system allows to combine in one unit features such as noise suppression, and general strengthening of the normal type and the desired signal. Commutative exchange of information between the sensors allows isolate the generator windings of the sensor from the measuring part of the analog interface, which considerably increases immunity. The algorithm for error correction of the measurement channel using TEDS in terms of non-linearity of the channel and the inter-channel connections is proposed. Results of the study can be implemented in the instrument-making factory in the design and development of new instruments for improving the accuracy and speed of linear and angular measurements using inductive displacement sensor for remote measurements.

Automatic Bridge-based Interface for Differential Capacitive Full Sensing

The authors here propose, for the first time, an automatic analog interface for differential capacitance estimation, able to reveal and quantify both low and high (full-range) capacitive variations. The working principle is based on a modified De-Sauty AC bridge configuration where two differential capacitances and two resistances are employed, one of which is implemented by a Voltage Controlled Resistor (VCR). Through a suitable feedback loop, a very accurate estimation over the complete range of the differential capacitance variation is possible, while the bridge allows a continuous differential capacitance evaluation without the need of knowing the accurate value of the sensor baseline and/or its variation range. A general but very simple formula, considering both the “autobalancing” and the “out-of-equilibrium” ranges, is also given. Theoretical, experimental and simulated results are in a very good agreement. Sensitivity and resolution values, typical of sensors and their interfaces, have been determined in a practical case, showing satisfactory values.

АНАЛОГОВИЙ ІНТЕРФЕЙС ДЛЯ ЄМНОСТІ ДАТЧИКА ПЕРЕМІЩЕНЬ З ВІДКРИТИМ ПОЛЕМ

An analytical review of existing methods for measuring small capacitances is performed. Analogue interface for remote measurements of initial parameters capacitance displacement sensors with an open field with improved metrological characteristics is designed.

SAI and NAI Experimental Interoperability Test

The connection with neighboring networks is fully automatic with some other military networks is manual with conventional manually operated networks. Interoperability of command, control and communication systems, and electronic interface of military communication systems are all critical issues in the modern battlefield. The ROK digital common user system, SPIDER, have been designed without joint operation concept at first. The ROK has developed a prototype SPIDER Analog Interface (SAI) device to provide U.S forces in Korea with the interoperability. The ROK SAI electrical characteristics were measured in the preliminary interoperability test in Korea, and the SAI and the U.S. NAI (NATO Analog Interface) device experimental interoperability test results are presented in this paper. From the preliminary interoperability test, the compatibility between the SAI and the NAI was verified.

Аналоговий інтерфейс індуктивного датчика переміщення

У статті описано датчики переміщення та важливість вимірювання переміщення як у авіаційній промисловості, так і у цивільній. У першій частині статті зроблено акцент на цивільному застосуванні описуваних датчиків як найбільш показовому. У межах цієї частини статті розглянуто різні типи пральних машин, важливість контролю різних параметрів у них та можливі результати поломок таких машин. Також оглянуто сучасні датчики переміщення у цій сфері, переваги та недоліки сучасних рішень, можливості для розвитку нових типів датчиків та відповідних аналогових інтерфейсів. Запропоновано новий аналоговий інтерфейс разом із індуктивним датчиком переміщення. Опис, схема, графік вихідного сигналу та формула підкріплюють запропоноване рішення. На основі наведеної інформації зроблені позитивні висновки щодо можливості корисного застосування запропонованої схеми.

Design and Implementation of a Teleprotection System with Digital and Analog Interfaces

Safe and un-interrupted power transmission requires a widespread use of control and protection equipment to avoid fault propagation in power network. Protection systems have been used to detect faults and block them to strike the high voltage lines. The teleprotection system continuously sends commands to remote substation in case of fault identification. Thus, the reliability and transmission time are vital issues to avoid intolerable errors. Teleprotection systems are interface between protection system and communication equipment. This paper proposes a digital teleprotection system to connect to digital communication network. The system is based on line interfaces and in accordance to ITU-T G.703 standard (64kbps and 2Mbps rates). Furthermore, the system benefits from the analog interface and direct analog voice band or optical fibers connection using eight independent commands. The system supports 8 channels simultaneously while its transmission time is 4ms at most.