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Journal ArticleDOI

A Linearizing Digitizer for Wheatstone Bridge Based Signal Conditioning of Resistive Sensors

15 Mar 2017-IEEE Sensors Journal (IEEE)-Vol. 17, Iss: 6, pp 1696-1705
TL;DR: A novel signal conditioning scheme, which provides a linear-digital output directly from the resistive sensor(s) that are connected in such bridge configurations, and drastically reduces the effect on the output due to the lead wires that connect the Wheatstone bridge and the DSADC.
Abstract: Output of a typical Wheatstone bridge, when it is connected to measure from a single or a dual resistive element, possesses non-linear characteristic. This paper presents a novel signal conditioning scheme, which provides a linear-digital output directly from the resistive sensor(s) that are connected in such bridge configurations. In the present scheme, the input stage of a dual-slope analog-to-digital converter (DSADC) is suitably augmented to incorporate the quarter-bridge and (or) half-bridge containing the resistive sensor as an integral part of the DSADC. A combination of the current mode excitation and wisely selected integration and de-integration operations of the DSADC enable to achieve linearization in the digitization process itself, leading to an overall reduction in the complexity level and number of blocks used keeping the high accuracy unaltered. A detailed analysis has been conducted to quantify the effect of various sources of errors in the output of the DSADC. The details are presented in the paper. The proposed method not only provides a linear digital output but also drastically reduces the effect on the output due to the lead wires that connect the Wheatstone bridge and the DSADC. Thus, the proposed scheme is well suited for the situations where the sensor(s) is (are) remotely located at a distance. Simulation studies as well as results from a prototype developed and tested establish the practicality of the proposed scheme. The inherent non-linearity of the Wheatstone bridge is reduced by nearly two orders of magnitude.
Citations
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Journal ArticleDOI
TL;DR: This paper presents a review of different methods applied to linearize sensor characteristics reported in the literature and concludes that the digital methods combined with software techniques perform the job with better flexibility and efficiency.
Abstract: Today, the sensing devices play an important role for various system automation and monitoring of different physical and chemical parameters. Nonlinearity is an important long-time issue for most of the sensors, so to compensate nonlinearity, various linearization schemes are reported in the literature. The accuracy of linearization schemes depends on the type and the nonlinearity value of the sensor output. Since it is difficult to find an exact polynomial equation or other functions to represent the response curve; it gives more error when the measurement parameter is determined from the inverse approximation functions. As many sensors are used for different applications, the linearized characteristics will simplify the design, calibration, and accuracy of the measurement. This paper presents a review of different methods applied to linearize sensor characteristics reported in the literature. Due to availability of high-performance analog devices, analog methods are still popular among many researchers. However, due to the advancement of IC technologies, hardware implementation of the software methods can be done easily with reduced time, cost, and more accuracy, so the digital methods combined with software techniques perform the job with better flexibility and efficiency.

19 citations


Cites background or methods from "A Linearizing Digitizer for Wheatst..."

  • ...…necessary signal conditioning circuits have been employed to linearize the response of thermistor, Hall effect sensor, and single or double resistive element Wheatstone bridge (Mohan et al., 2008; Mohan et al., 2011; Sreekantan and George, 2014; Ramadoss and George, 2015; Nagarajan et al., 2017)....

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  • ...Recently, conventional dual slope analog to digital converter with necessary signal conditioning circuits have been employed to linearize the response of thermistor, Hall effect sensor, and single or double resistive element Wheatstone bridge (Mohan et al., 2008; Mohan et al., 2011; Sreekantan and George, 2014; Ramadoss and George, 2015; Nagarajan et al., 2017)....

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  • ...(Nagarajan et al., 2017) Dual slope ADC for direct interface to μC (quarter/half bridge resistive sensors) <0....

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Journal ArticleDOI
TL;DR: This article proposes simple relaxation-oscillator-based digital interfacing schemes for resistive sensors in single-element and quarter-bridge forms, equipped with novel compensation techniques, that render a direct-digital output proportional to sensor resistance.
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.

14 citations


Cites background from "A Linearizing Digitizer for Wheatst..."

  • ...However, these schemes require precision (matched) reference voltages and works in [11] need an additional phase to start the conversion....

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  • ...Alternatively, the work in [11] makes the output independent of wire resistance using instrumentation amplifier (IA) and an involved switching logic....

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  • ...Simple dual-slope-based circuits for different types of resistive sensors are reported in [10] and [11]....

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  • ...A number of digital techniques, such as pulsewidth conversion [7]–[9], dual slope [10], [11], direct microcontroller interfacing [12]–[15], sigma-delta [16], and relaxation oscillator [17]–[21], are prevalent for resistive sensors....

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Journal ArticleDOI
TL;DR: Analog signal conditioning circuit based on dual differential subtractor for wide range resistive measurement of single element resistive sensor is presented in this paper, which helps to achieve high accuracy and wide dynamic range by generating a control voltage proportional to the sensor resistance.
Abstract: Analog signal conditioning circuit based on dual differential subtractor for wide range resistive measurement of single element resistive sensor is presented in this paper. The differential output from the sensor and a voltage-controlled reference resistor is followed by an auto-nulling technique, which helps to achieve high accuracy and wide dynamic range by generating a control voltage proportional to the sensor resistance. The presented automatic approach not only enhances the auto-nulling range but also ensures constant sensitivity. The interface design provides high accuracy, fast and linear response at the same time avoids drawbacks of lead wire variations. A prototype PCB of the proposed circuit is fabricated and tested. The experimental result shows that the circuit can measure a wide range of resistance (20 $\text{k}\Omega $ - 1.1 $\text{M}\Omega$ ) with relative error less than 0.78%, compared to other bridge-based circuits which are capable of measuring the maximum resistance of up-to 10 $\text{k}\Omega $ for the same accuracy. Multiple variations of the proposed circuit are designed and experimentally tested for verifying the tunability of the circuit in terms of the sensitivity and the range of resistance measurement. The prototype circuit is also interfaced with an in-house fabricated MEMS-based ammonia sensor, proving its efficacy in resistive sensor system development.

13 citations


Cites background from "A Linearizing Digitizer for Wheatst..."

  • ...To handle these dynamic properties robust signal conditioning circuits are required [8], [9]....

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  • ...However, the Wheatstone bridge is not preferable for single elements resistive sensors due to high non-linearity [1], [9]....

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Journal ArticleDOI
TL;DR: A fully analog method has been introduced in order to implement a null measurement instrument for a resistive Wheatstone bridge with a single resistive sensor to evaluate the performance and usefulness of the proposed method.
Abstract: When high-speed measurements are not necessary, the Wheatstone bridge-based null measurement instruments surpass the Wheatstone Bridge-based instruments using deflection technique, due to the fact that the null method has some intrinsic advantages over the deflection method. In this particle, a fully analog method has been introduced in order to implement a null measurement instrument for a resistive Wheatstone bridge with a single resistive sensor. In order to implement the proposed circuit, only two operational amplifiers and some passive elements have been used. The proposed method can be constructed and implemented by discrete components without any special limitation. Since the suggested scheme has linear output, the required computation in order to measure and display the measurand is reduced dramatically. Finally, in order to evaluate the performance and usefulness of the proposed method, it has been tested experimentally as well as by using computer aided design software.

12 citations

Journal ArticleDOI
28 Jul 2020-Sensors
TL;DR: In this work, excellent characteristics of LT199x selectable gain amplifiers are exploited to precisely divide an input current, and an excellent linearity is found with a relative error within ±0.1% after a preliminary calibration procedure.
Abstract: Highly accurate and stable current references are especially required for resistive-sensor conditioning. The solutions typically adopted in using resistors and op-amps/transistors display performance mainly limited by resistors accuracy and active components non-linearities. In this work, excellent characteristics of LT199x selectable gain amplifiers are exploited to precisely divide an input current. Supplied with a 100 µA reference IC, the divider is able to exactly source either a ~1 µA or a ~0.1 µA current. Moreover, the proposed solution allows to generate a different value for the output current by modifying only some connections without requiring the use of additional components. Experimental results show that the compliance voltage of the generator is close to the power supply limits, with an equivalent output resistance of about 100 GΩ, while the thermal coefficient is less than 10 ppm/°C between 10 and 40 °C. Circuit architecture also guarantees physical separation of current carrying electrodes from voltage sensing ones, thus simplifying front-end sensor-interface circuitry. Emulating a resistive-sensor in the 10 kΩ–100 MΩ range, an excellent linearity is found with a relative error within ±0.1% after a preliminary calibration procedure. Further advantage is that compliance voltage can be opposite in sign of that obtained with a passive component; therefore, the system is also suitable for conditioning active sensors.

12 citations


Cites methods from "A Linearizing Digitizer for Wheatst..."

  • ...Several linearization techniques have been reported, as the Current Mode WB [11], switches driven integration/deintegration method [12], and the double differential potential subtractor [13]....

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References
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Proceedings ArticleDOI
07 Aug 2002
TL;DR: In this article, a low-cost CMOS interface circuit for resistive bridge transducers is proposed, which provides amplification as well as temperature, gain and offset compensation in the analog domain, and linearization and PWM conversion in the digital domain.
Abstract: A low-cost CMOS interface circuit for resistive bridge transducers is fully designed and implemented. It provides amplification as well as temperature, gain and offset compensation in the analog domain, and linearization and PWM conversion in the digital domain. An experimental prototype interfaces a magnetoresistive bridge as a particular example, thus demonstrating the validity of the proposed approach.

11 citations

01 Jan 2000
TL;DR: In this paper, a new circuit topology based on duality of well known voltage-mode Wheatstone bridge is described, which can implement ratiometric current measurement which is a vital aspect of current-mode instrumentation and signal processing.
Abstract: This paper describes a new circuit topology based on duality of well known voltage-mode Wheatstone bridge. This topology can implement ratiometric current measurement which is a vital aspect of current-mode instrumentation and signal processing. Theory of the proposed circuit is developed and its advantages and limitations are discussed. The new circuit (being called AZKA cell) may be thought of as the current-mode alterna- tive of traditional voltage-mode Wheatstone bridge. It presents the current-mode circuit designers and engineers their own relevant interface cell. The advantages of the new circuit are stated and some conditioning circuits for its output signal are proposed. Finally, a linearization circuit based on CCII is introduced. Index Terms—AZKA cell, CCII, current cell, current-mode.

5 citations


"A Linearizing Digitizer for Wheatst..." refers background or methods in this paper

  • ...of using current driven Wheatstone bridge and its variants are discussed in [10]–[13]....

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  • ...Current Mode Wheatstone Bridge (CMWB) based on duality concept is reported [10]....

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Proceedings ArticleDOI
27 Jul 2014
TL;DR: An alternative linear topology for conditioning resistive sensors is presented, which allows for an inherently linear relationship between the variable measured by the sensor and its corresponding output, which is not always valid for the topologies most commonly employed in industrial applications.
Abstract: This paper presents an alternative linear topology for conditioning resistive sensors. This topology allows us to obtain an inherently linear relationship between the variable measured by the sensor and its corresponding output, which is not always valid for the topologies most commonly employed in industrial applications, such as the Wheatstone bridge. SPICE simulations of this alternative topology as a CMOS integrated circuit in 0.5μm technology has demonstrated not only its functionality and linearity, but also its superiority over the Wheatstone bridge.

1 citations