Elangovan K

Bio: Elangovan K is an academic researcher from Indian Institute of Space Science and Technology. The author has contributed to research in topics: Relaxation oscillator & Parasitic capacitance. The author has an hindex of 3, co-authored 12 publications receiving 25 citations.

Performance Verification of a Digital Interface Suitable for a Broad Class of Resistive Sensors

Abstract: An improved digital interface circuit for resistive sensors is proposed in this paper. The circuit offers many positive features, such as (1) use of single-reference voltage in its architecture, (2) facility to tune/preset the sensor-excitation current, even for different values of resistive sensors, (3) minimal dependence on many circuit non-ideal parameters. The working of the circuit is mathematically described in this paper, followed by its extensive error evaluation. Detailed simulation and experimental studies are performed to verify the feasibility of the interface for three different types of sensors. These studies show that the circuit can efficiently be used in temperature-monitors, magnetometers, and displacement-sensing. The maximum experimental nonlinearity observed from all of these sensor configurations does not exceed 0.06 %. Then, the extensive studies are carried out by simulation as well as experimentation to show the effect of environmental temperature changes on the proposed circuit. Finally, the proposed circuit is compared with some of the recent resistive digital interfaces.

Simple and Efficient Relaxation-Oscillator-Based Digital Techniques for Resistive Sensors — Design and Performance Evaluation

Abstract: This article proposes simple relaxation-oscillator-based digital interfacing schemes for resistive sensors in single-element and quarter-bridge forms. The proposed interfaces, equipped with novel compensation techniques, render a direct-digital output proportional to sensor resistance. These interfaces offer many meritorious features, such as simplicity of design, nonrequirement of the reference voltage, lower execution time, and negligible influences from circuit nonidealities. The methodology of the interfaces and their design criteria and error analysis are described in this article. The first two interfaces are suitable for nonremote resistive sensors, while the third interface has been developed for remotely located resistive sensors. The functionality of the proposed interfaces has been verified using simulation as well as detailed experimental studies. The developed interfaces provide a linear direct-digital output, and the maximum experimental nonlinearity is merely 0.08%. Later, a representative sensor based on the giant magnetoresistance (GMR) phenomenon is selected, characterized, and tested with the developed interfaces. The complete instrumentation system is shown to act as a linear digital magnetometer. Finally, the performance of the developed interfaces is compared and shown to be better/comparable with respect to the existing works.

Evaluation of New Digital Signal Conditioning Techniques for Resistive Sensors in Some Practically Relevant Scenarios

Abstract: Resistive sensors, with wide-span of operation, are used in a number of industrial scenarios. In some of these cases, such resistive sensors may need to be located in a remote environment, away from the electronics unit. This article brings-forth new and efficient digital signal conditioning techniques to interface the aforementioned classes of resistive sensors. The first proposed technique employs a simple circuitry that requires a single reference voltage and single operation cycle and provides a direct-digital output proportional to the sensor-resistance. Next, this scheme is further enhanced, with the addition of few auxiliary components, to address the case of remotely-located resistive sensors. The novel circuit-designs also ensure other positive features like: 1) short execution time; 2) compatibility to resistive sensors in different configurations; and 3) negligible dependence on many nonideal parameters. The proposed schemes are systematically presented and thoroughly analyzed in this article. Elaborate simulation and emulation studies are used to evidence the performance. A maximum nonlinearity of 0.07% and 12-bit resolution is obtained for the first digitizer, during the hardware tests. The utility of the schemes to interface a temperature sensor with wide-span is also studied. Vital performance parameters of the schemes are derived and compared with the state-of-art works.

An Efficient Universal Digitizer With Linear Transfer Characteristic for Resistive Sensor Bridges

Abstract: A simple digitizer circuit suitable for bridge-based resistive sensors is reported in this article. The digitizer provides a linear transfer characteristic, for all common types of resistive bridges. Besides, the digitizer output is independent of the parasitic capacitance of the resistive sensors, connecting wire impedances, and mismatch among the bridge elements. The methodology of the digitizer is mathematically derived and analyzed. A number of experimental studies of the digitizer are carried out with various types of bridge configurations. Linear output characteristic, with all other expected meritorious features, is obtained during all these tests, and the maximum output nonlinearity is less than 0.06%. Tests are also conducted with an industrial magnetoresistance (MR) sensor bridge. The results demonstrate a magnetic sensing system with higher performance when compared with the conventional interface for MR sensors.

A Simple Digital Interface Circuit for Giant Magneto-Resistance Sensors

Abstract: Giant Magneto-Resistance (GMR) sensor-elements are usually configured in a Wheatstone bridge form. In this work, a new simple interface circuit with a microcontroller is proposed to identify the fractional-resistance change of GMR sensor using the discharge times of the capacitor. An Op-amp is used to avoid the effect of the mismatch of unshielded-resistance of the GMR sensor. This method just uses three conversion modes to make the output immune to the pin-resistance of the microcontroller. Simulation and emulation studies of the proposed interface are performed. A worst-case nonlinearity of 0.35% is observed. A hardware model of the interface is tested with the GMR sensor and the associated results are also reported in this paper.

Simple and Efficient Relaxation-Oscillator-Based Digital Techniques for Resistive Sensors — Design and Performance Evaluation

Abstract: This article proposes simple relaxation-oscillator-based digital interfacing schemes for resistive sensors in single-element and quarter-bridge forms. The proposed interfaces, equipped with novel compensation techniques, render a direct-digital output proportional to sensor resistance. These interfaces offer many meritorious features, such as simplicity of design, nonrequirement of the reference voltage, lower execution time, and negligible influences from circuit nonidealities. The methodology of the interfaces and their design criteria and error analysis are described in this article. The first two interfaces are suitable for nonremote resistive sensors, while the third interface has been developed for remotely located resistive sensors. The functionality of the proposed interfaces has been verified using simulation as well as detailed experimental studies. The developed interfaces provide a linear direct-digital output, and the maximum experimental nonlinearity is merely 0.08%. Later, a representative sensor based on the giant magnetoresistance (GMR) phenomenon is selected, characterized, and tested with the developed interfaces. The complete instrumentation system is shown to act as a linear digital magnetometer. Finally, the performance of the developed interfaces is compared and shown to be better/comparable with respect to the existing works.

A Novel Linearizing Signal Conditioner for Half-Bridge-Based TMR Angle Sensor

Abstract: This paper proposes a novel signal conditioning circuit for half-bridge topology based Tunneling Magneto-Resistance (TMR) angle sensor. The resistances of TMR angle sensor vary as a sine/cosine function of the shaft angle. The proposed circuit employs an enhanced dual-slope technique to process these non-linear resistance variations and render a linear digital output for full-circle range. The circuit uses easily available and low-cost circuit components, and a novel linearization logic in its architecture. It possesses low dependence on many circuit and sensor non-idealities. Further, a novel algorithm is proposed to reduce the measurement error due the mismatch in nominal resistances of the TMR sensor. The working of the circuit is verified using simulation as well as experimental studies. The maximum non-linearity in the circuit output, observed with expected sine/cosine characteristic, is 0.038 %. Later, a shaft angle sensing unit, employing AAT003-10E half-bridge TMR angle sensor IC, is designed, built, and characterized. The interfacing studies showcase the capability of the developed signal conditioning circuit for linearizing practical TMR angle sensors. The efficacy of the compensation algorithm is also proved in the experimentation.

Evaluation of New Digital Signal Conditioning Techniques for Resistive Sensors in Some Practically Relevant Scenarios

Abstract: Resistive sensors, with wide-span of operation, are used in a number of industrial scenarios. In some of these cases, such resistive sensors may need to be located in a remote environment, away from the electronics unit. This article brings-forth new and efficient digital signal conditioning techniques to interface the aforementioned classes of resistive sensors. The first proposed technique employs a simple circuitry that requires a single reference voltage and single operation cycle and provides a direct-digital output proportional to the sensor-resistance. Next, this scheme is further enhanced, with the addition of few auxiliary components, to address the case of remotely-located resistive sensors. The novel circuit-designs also ensure other positive features like: 1) short execution time; 2) compatibility to resistive sensors in different configurations; and 3) negligible dependence on many nonideal parameters. The proposed schemes are systematically presented and thoroughly analyzed in this article. Elaborate simulation and emulation studies are used to evidence the performance. A maximum nonlinearity of 0.07% and 12-bit resolution is obtained for the first digitizer, during the hardware tests. The utility of the schemes to interface a temperature sensor with wide-span is also studied. Vital performance parameters of the schemes are derived and compared with the state-of-art works.

Simplified Digitizing Interface-Architectures for Three-Wire Connected Resistive Sensors: Design and Comprehensive Evaluation

Abstract: This article describes the design, analysis, and performance verification of simple digitizing interfaces for different types of three-wire resistive sensors. The proposed interface uses an efficient resistance-to-time conversion technique that charges an internal capacitor, between two reference levels, through selected resistive-sensor paths. A simple analog circuit controlled using a digital timing unit realizes the aforementioned technique. This approach is adaptable for various resistive sensor configurations and does not depend on the effect of connecting wire resistances and various other non-ideal parameters (e.g., threshold voltage and pin resistance of microcontroller, offset voltage of comparator, etc.). In addition, the proposed schemes utilize its digital unit (e.g., microcontroller) only for control and timing operations, thus saving on power. The detailed working principle of the proposed interfaces and their error analysis are discussed in the article. Later, performance verification is carried out using simulation as well as emulation studies. These studies clearly show that the presented digitizing interfaces provide linear digital transfer characteristics with maximum nonlinearity of 0.17% and wire resistance compensation. Further, tests are conducted with various remotely located commercial sensors. The outcomes of these studies are reported and compared with the state-of-the-art works.

Linearized Sigma–Delta-Based Direct Digital Converter for GMR Sensors

Abstract: A direct digital converter, based on the sigma–delta modulation principle, is proposed in this article for giant magnetoresistance (GMR) sensors. The proposed converter intelligently integrates the GMR sensors with an improved sigma–delta modulator and provides a linear digital indication of the input magnetic field. The digital output is obtained directly, without using any analog-to-digital converter modules. Some additional merits of the proposed interface are: 1) requirement of a single reference voltage; 2) easy-to-use facility to tune/enhance the overall sensitivity; 3) low conversion time etc. The modulator circuit is followed by a digital filter and decimation circuit, implemented in a microcontroller unit. This sigma–delta converter is validated extensively using simulation and emulation studies. The results from these studies corroborate well, and the maximum nonlinearity is found to be less than 0.12%. Finally, an experimental prototype is developed with a GMR sensor, and the functionality of the converter is tested for static and time-varying field inputs. The experimental nonlinearity of 0.69% shows the better performance of the proposed scheme with respect to other digital digitizer circuits present in the literature.