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Shahid Malik

Bio: Shahid Malik is an academic researcher from Indian Institute of Technology Bombay. The author has contributed to research in topics: Capacitive sensing & Capacitance. The author has an hindex of 8, co-authored 32 publications receiving 176 citations. Previous affiliations of Shahid Malik include Council of Scientific and Industrial Research & Academy of Scientific and Innovative Research.

Papers
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Journal ArticleDOI
TL;DR: In this article, a simple and accurate impedance measurement technique (IMT) for wide range lossy capacitive sensor is proposed, which is based on the separation of in-phase and quadrature components.
Abstract: In this paper, a new, simple and accurate impedance measurement technique (IMT) for wide range lossy capacitive sensor is proposed. The proposed technique accepts sensors having capacitance ‘Cx’ with lossy resistance ‘Rx’ in parallel. The proposed IMT is based on the separation of in-phase and quadrature components, which is achieved by using phase to time converter. For comparative study, two circuit configurations are proposed. In first proposed solution, the sensor parameters are measured by separating the real and imaginary part of the output electrical signal. In the second proposed configuration, the measurement range is enhanced using an auto-balancing approach, which is achieved by monitoring phase difference between input and output voltages. Experimental evaluation of the proposed configurations reveals that the first configuration is able to estimate the sensor capacitance in the range 200–1200 pF and lossy resistance in the range of 100 kΩ–1.2 MΩ with a maximum error of 6%. The second configuration exhibits an enhanced range of 100–2000 pF for sensor capacitance and 33 kΩ–3 MΩ for lossy resistance with a maximum error of 5%. The IMT was interfaced with a fabricated γ-Al2O3 based impedance humidity sensor, measured its Cx (70 pF–800 pF) and Rx (35 kΩ–4 MΩ) at different concentration of humidity, calculated the humidity, and compared its performance with existing techniques, showing the practicality of the proposed IMT.

43 citations

Proceedings ArticleDOI
01 Oct 2018
TL;DR: This study proposes a low-cost capacitive sensor fabricated using screen printing of carbon paste interdigitated electrodes on paper substrate for respiration monitoring, and shows better response time compared to resistive configuration.
Abstract: Respiration is a key vital sign indicative of an individual's health. Current approaches of respiration sensing require direct contact with the body. Moreover, they are expensive and need bulky holter monitors for continuous realtime monitoring. In this study, we propose a low-cost capacitive sensor fabricated using screen printing of carbon paste interdigitated electrodes on paper substrate for respiration monitoring. Cellulosic paper provides a microporous network to trap exhaled breath. Respiration causes the dielectric constant of the paper to change, mostly as a function of breath humidity, which in turn changes the capacitance of the sensor. The interdigitated electrodes configuration is shown to provide better response time compared to resistive configuration. A simple phase sensitive detector-based circuit was used to convert the capacitance change into a measurable output voltage. The MSP430 microcontroller was used for data acquisition and voltage measurement. A graphical user interface was designed for real time respiration monitoring. Experimental results validate the performance of this sensor.

26 citations

Journal ArticleDOI
TL;DR: A half-bridge-based versatile, four-phase auto-calibration-based differential and ratiometric operation is used to compensate for the baseline resistance of the sensor and the mismatches due to the non-ideal circuit parameters.
Abstract: Most of the resistive sensors have a large baseline resistor and a relatively small incremental change in the resistor value due to the measurand. A half-bridge-based versatile $\Delta R/R_{s}$ measurement system for a wide range of resistive sensors is reported in this article. A four-phase auto-calibration-based differential and ratiometric operation is used to compensate for the baseline resistance of the sensor and the mismatches due to the non-ideal circuit parameters. A low-noise application-specific current generator and low noise, high CMRR current-mode instrumentation amplifier is designed and fabricated in UMC 180-nm technology. A prototype board of the $\Delta R/R_{s}$ measurement system is developed and tested. The experimental results show that the proposed system is able to detect even smaller ppm level of about 72 ppm of $\Delta R/R_{s}$ for the base resistor $R_{s}$ value as high as 0.5 $\text{M}\Omega $ with a relative error of less than ±1%. The effect of the parasitic capacitors on the sensor response is also tested experimentally. Finally, the proposed system is tested with an in-house fabricated displacement sensor.

26 citations

Journal ArticleDOI
30 May 2019
TL;DR: An accurate impedance-to-time converter (ITC) circuit for leaky capacitive sensors that is able to deal with these problems and estimate the sensor capacitor and leaky resistor is presented in this article.
Abstract: Capacitive sensors suffer from problems of the parasitic and offset capacitors. Also, in some capacitive sensors, leaky resistors carry information along with the sensor capacitor. An accurate impedance-to-time converter (ITC) circuit for leaky capacitive sensors that is able to deal with these problems and estimate the sensor capacitor and leaky resistor is presented in this article. The proposed circuit is a modified relaxation oscillator, which combines dual slope and charge transfer methods to measure the sensor capacitor and leaky resistor. The output pulses of the oscillator are acquired, and pulsewidth corresponding to high and low pulse are extracted and averaged. The effect of dc errors and jitter are significantly reduced because of the averaging. A prototype of the proposed ITC has been developed and tested. Experimental results show that the proposed ITC can measure low values of the sensor capacitor (minimum 9.6 pF) in the presence of a wide range of leaky resistors (270 kΩ to 9.6 MΩ) and offset capacitors (9.6 pF to 543.4 pF) with a worst-case error of about 1.1%, as compared to the theoretical values. The targeted application for the designed circuit is the humidity sensor with a frequency range between 500 Hz and 5 kHz.

25 citations

Journal ArticleDOI
TL;DR: In this paper, a fully analog auto-nulling bridge based capacitance-to-voltage (AN-C2V) converter circuit is presented for measuring the capacitive component of the leaky capacitive sensors.
Abstract: This paper presents a fully analog auto-nulling bridge based capacitance-to-voltage (AN-C2V) converter circuit for measuring the capacitive component of the leaky capacitive sensors. The circuit utilizes an active bridge based architecture in which the quadrature components of the output are taken. An integrator-controller is used for auto-nulling. A unity gain, frequency-independent quadrature phase shift amplifier is designed for an accurate generation of 90° phase-shifted signal. Experiments conducted on the developed prototype demonstrate that the proposed AN-C2V system is able to estimate the sensor capacitor ranging from 47.2pF to 668.3pF with a maximum error of about ± 0.18% with respect to the commercial LCR meter. The effectiveness of the circuit is tested with the commercial leaky capacitive humidity sensor. The effect of leakage resistor, parasitic capacitor, frequency of excitation signal, and supply voltage is negligible on the final output, which results in a very robust and accurate solution for leaky capacitive sensors.

24 citations


Cited by
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01 Apr 1983

405 citations

01 Jan 2016
TL;DR: In this paper, a handbook of modern sensors physics designs and applications and applications are discussed. But instead of reading a good book with a cup of coffee in the afternoon, instead they juggled with some malicious bugs inside their laptop.
Abstract: Thank you for reading handbook of modern sensors physics designs and applications. As you may know, people have search hundreds times for their chosen readings like this handbook of modern sensors physics designs and applications, but end up in infectious downloads. Rather than reading a good book with a cup of coffee in the afternoon, instead they juggled with some malicious bugs inside their laptop.

249 citations

Journal ArticleDOI
TL;DR: The results indicated that contextual information incorporated into recommendations can be categorised into three contexts, namely users' context, document's context, and environment context, which indicates the classical approaches such as collaborative filtering were employed more than the other approaches.
Abstract: We review the relevant articles in the field of scholar recommendations.We explore contextual information influential in scholar recommendations.We examine recommending approaches.Contextual information are categorised in three groups.The most recommending approaches are collaborative filtering, content based, knowledge based and hybrid. Incorporating contextual information in recommender systems is an effective approach to create more accurate and relevant recommendations. This review has been conducted to identify the contextual information and methods used for making recommendations in digital libraries as well as the way researchers understood and used relevant contextual information from the years 2001 to 2013 based on the Kitchenham systematic review methodology. The results indicated that contextual information incorporated into recommendations can be categorised into three contexts, namely users' context, document's context, and environment context. In addition, the classical approaches such as collaborative filtering were employed more than the other approaches. Researchers have understood and exploited relevant contextual information through four ways, including citation of past studies, citation of past definitions, self-definitions, and field-query researches; however, citation of the past studies has been the most popular method. This review highlights the need for more investigations on the concept of context from user viewpoint in scholarly domains. It also discusses the way a context-aware recommender system can be effectively designed and implemented in digital libraries. Additionally, a few recommendations for future investigations on scholarly recommender systems are proposed.

122 citations

Journal ArticleDOI
TL;DR: The article offers the fundamental guideline on the sensing mechanisms and design concepts of stretchable sensors for detecting vital breath signals such as temperature, humidity, airflow, stress and strain.

110 citations

Journal ArticleDOI
TL;DR: The materials, characterization methods, and fabrication methods implemented for the development of the printed and flexible sensors, and the applications, challenges faced and future opportunities are presented.

66 citations