Quantum computing promises an exponentially higher computational power than classical computers; ... more Quantum computing promises an exponentially higher computational power than classical computers; although all the building blocks have become available, certain constraints still prevent quantum advantage. The fundamental challenge in building a practical quantum computer is integrating thousands of highly coherent qubits with the control and readout electronics. The need for a high‐coherence qubit drives the effort for quantum error correction algorithms to create fault‐tolerant quantum systems. Error correction becomes tangible in a quantum processor only in large numbers of qubits. Thus, the other challenge is reducing the number of physical interconnects (coaxial lines) between the quantum–classical interface and bulky room‐temperature electronics. To interface thousands of qubits, interconnects can be reduced by bringing the control and readout electronics near the quantum processor. Cryogenic complementary metal–oxide–semiconductor (CMOS) technology has been an ideal candidate...
2020 IEEE International Conference on Flexible and Printable Sensors and Systems (FLEPS)
A flexible dry ECG patch for continuous heart rate variablity monitoring is presented in this pap... more A flexible dry ECG patch for continuous heart rate variablity monitoring is presented in this paper. A flexible dry ECG patch with a polymide substrate was designed. The hardware compromises of an ECG front end, an ultra low power controller for wireless Bluetooth data transmission and a power management block. The ECG electrodes were also fabricated on the flip-side of the same polymide substrate. The electrodes were screen printed on the flexible polymide substrate using carbon ink. We demonstrate the working of the flexible dry ECG patch with experimental data on a human subject.
2020 IEEE 17th India Council International Conference (INDICON)
An accurate auto-tunable quadrature-phase generator circuit based on phase-sensitive-detection an... more An accurate auto-tunable quadrature-phase generator circuit based on phase-sensitive-detection and auto-nulling feedback loop for capacitive and impedance sensors is presented in this paper. The core of the phase-generator circuit consists of an operational amplifier based modified all-pass filter circuit with a voltage controlled resistor. The phase-shift of the modified all-pass circuit is compared with the input signal using phase-sensitive-detection technique and, accordingly the auto-nulling loop controls the value of the voltage controlled resistor to maintain a quadrature-phase shift. A prototype of the circuit is designed and experimentally tested by varying the frequency of the input signal from 600 Hz to 1.4 kHz. The circuit shows excellent accuracy with a maximum phase-error within 1 degree. The efficacy of the circuit is further tested with for measuring the capacitance of the impedance R-C sensors.
2020 IEEE International Conference on Flexible and Printable Sensors and Systems (FLEPS), 2020
In this paper a simple and low-cost 3D printed robotic finger is presented. The 3D printed finger... more In this paper a simple and low-cost 3D printed robotic finger is presented. The 3D printed finger is embedded with a low-cost flexible piezoresistive polymer for sensing pressure and a thread-based carbon coated strain sensor for tracking the bending of the finger. The fingers are 3D printed with fused deposition modeling (FDM) printers using polymer composites thereby enabling low cost, high speed and simplicity. Design of a single such 3D printed finger is discussed and results are shown for the embedded pressure and strain sensors using a simple highly linear analog readout circuit.
Respiration is a key vital sign indicative of an individual's health. Current approaches of r... more 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 graphi...
This work presents the development of a robotic hand using 3D printing technology for robotic and... more This work presents the development of a robotic hand using 3D printing technology for robotic and prosthetic applications. The 3D printed hand presented herein is very cost-effective and involves elementary fabrication steps paving the way for rapid manufacturing at low cost. Fused deposition modeling (FDM) printers using polymer composites are used to print with optimized manufacturing settings to achieve a truly low-cost solution through minimal waste, minimal material requirement while achieving the required durability. Further, the 3D printed hand is embedded with pressure and strain sensors for tactile feedback required for human-like dexterity. A piezoresistive polymer-based flexible pressure sensor and an in-house carbon-coated elastic thread-based strain sensor are employed to realize the cost-effective 3D printed hand with tactile feedback. The sensors employed need a highly linear readout circuit for the effective implementation of the tactile feedback. Owing to this, a hi...
2020 IEEE International Conference on Flexible and Printable Sensors and Systems (FLEPS)
A simple, low cost, screen-printed flexible capacitive sensor for moisture, and water level detec... more A simple, low cost, screen-printed flexible capacitive sensor for moisture, and water level detection is presented in this paper. The sensor is fabricated on the flexible polyamide substrate. The interdigitated structure electrodes are screen printed on the substrate to form the capacitive fingers using carbon paste. The relative permittivity of the medium changes due to the water vapors on the sensor, which in turn changes the capacitance of the sensor due to the fringing field. A novel auto-nulling based signal conditioning circuit was utilized to measure the capacitance of the sensor. The flexible nature of the sensor enhances the use of the fabricated capacitive sensor in applications such as diaper wetness monitoring, soil moisture monitoring, body hydration monitoring.
An accurate auto-tunable quadrature-phase generator circuit based on phase-sensitive-detection an... more An accurate auto-tunable quadrature-phase generator circuit based on phase-sensitive-detection and auto-nulling feedback loop for capacitive and impedance sensors is presented in this paper. The core of the phase-generator circuit consists of an operational amplifier based modified all-pass filter circuit with a voltage controlled resistor. The phase-shift of the modified all-pass circuit is compared with the input signal using phase-sensitive-detection technique and, accordingly the auto-nulling loop controls the value of the voltage controlled resistor to maintain a quadrature-phase shift. A prototype of the circuit is designed and experimentally tested by varying the frequency of the input signal from 600 Hz to 1.4 kHz. The circuit shows excellent accuracy with a maximum phase-error within 1 degree. The efficacy of the circuit is further tested with for measuring the capacitance of the impedance R-C sensors.
Sensor platforms that exploit the fibrous textile threads as substrates offer great promise since... more Sensor platforms that exploit the fibrous textile threads as substrates offer great promise since they can be directly sewn, woven or stitched on to any clothing. They can also be placed directly in intimate contact with the skin. In this work, we present a thread-based sensing platform in the form of a multiplexed sensing patch for continuous simultaneous on-skin monitoring of sweat. The patch performs real-time, on-body measurements of important biomarkers present in sweat such as electrolytes (sodium and ammonium ions), metabolites (lactate) and acidity (pH). Flexible threads coated with conductive inks were used as sensing electrodes. Selective potentiometric detection of electrolytes and pH was made possible through ion-selective membrane deposition and pH-sensitive polyaniline coating on threads, respectively. An amperometric enzymatic sensing scheme with lactate oxidase was used for the detection of lactate. An array of the thread sensors is integrated onto a patch with conne...
Most of the resistive sensors have a large baseline resistor and a relatively small incremental c... more 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 <inline-formula> <tex-math notation="LaTeX">$\Delta R/R_{s}$ </tex-math></inline-formula> 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 <inline-formula> <tex-math notation="LaTeX">$\Delta R/R_{s}$ </tex-math></inline-formula> 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 <inline-formula> <tex-math notation="LaTeX">$\Delta R/R_{s}$ </tex-math></inline-formula> for the base resistor <inline-formula> <tex-math notation="LaTeX">$R_{s}$ </tex-math></inline-formula> value as high as 0.5 <inline-formula> <tex-math notation="LaTeX">$\text{M}\Omega $ </tex-math></inline-formula> 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.
IEEE Transactions on Instrumentation and Measurement
In this article, we propose an autonulling-based multimode impedance-to-voltage converter (AN-Z2V... more In this article, we propose an autonulling-based multimode impedance-to-voltage converter (AN-Z2V) signal conditioning circuit for resistive–capacitive (R-C) sensors. The proposed technique takes advantage of the reuse of the phase tracking and autonulling modules to extract the in-phase and quadrature components of the sensors. The circuit is designed for three sensing modes: 1) Mode-C for capacitive sensors with leakage resistor; 2) Mode-R for resistive sensors with parasitic shunt capacitor; and 3) Mode-Z for impedance R-C sensor. A novel autotuning quadrature phase generator circuit is designed and implemented for the generation of reference 90° phase-shifted signal for the leaky capacitive sensors. A prototype of the proposed circuit is fabricated and tested. Measurement results show that AN-Z2V provides the measurement range with low relative error compared with the reported systems. The system is tested for a range of 10–760 pF and 56 <inline-formula> <tex-math notation="LaTeX">$\text{k}\Omega $ </tex-math></inline-formula>–6.5 <inline-formula> <tex-math notation="LaTeX">$\text{M}\Omega $ </tex-math></inline-formula> for mode-C and mode-R, respectively. The accuracy of the proposed circuit is found to be ±0.11% and ±0.07% for mode-C and mode-R, respectively. The capacitance and resistance of the impedance R-C sensor are simultaneously measured in mode-Z for a range of 33–528 pF and 100 <inline-formula> <tex-math notation="LaTeX">$\text{k}\Omega $ </tex-math></inline-formula>–7.8 <inline-formula> <tex-math notation="LaTeX">$\text{M}\Omega $ </tex-math></inline-formula>, respectively.
This paper presents a fully analog auto-nulling bridge based capacitance-to-voltage (AN-C2V) conv... more 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 $\pm ~0.18\%$ 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.
Capacitive sensors suffer from problems of the parasitic and offset capacitors. Also, in some cap... more 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.
Quantum computing promises an exponentially higher computational power than classical computers; ... more Quantum computing promises an exponentially higher computational power than classical computers; although all the building blocks have become available, certain constraints still prevent quantum advantage. The fundamental challenge in building a practical quantum computer is integrating thousands of highly coherent qubits with the control and readout electronics. The need for a high‐coherence qubit drives the effort for quantum error correction algorithms to create fault‐tolerant quantum systems. Error correction becomes tangible in a quantum processor only in large numbers of qubits. Thus, the other challenge is reducing the number of physical interconnects (coaxial lines) between the quantum–classical interface and bulky room‐temperature electronics. To interface thousands of qubits, interconnects can be reduced by bringing the control and readout electronics near the quantum processor. Cryogenic complementary metal–oxide–semiconductor (CMOS) technology has been an ideal candidate...
2020 IEEE International Conference on Flexible and Printable Sensors and Systems (FLEPS)
A flexible dry ECG patch for continuous heart rate variablity monitoring is presented in this pap... more A flexible dry ECG patch for continuous heart rate variablity monitoring is presented in this paper. A flexible dry ECG patch with a polymide substrate was designed. The hardware compromises of an ECG front end, an ultra low power controller for wireless Bluetooth data transmission and a power management block. The ECG electrodes were also fabricated on the flip-side of the same polymide substrate. The electrodes were screen printed on the flexible polymide substrate using carbon ink. We demonstrate the working of the flexible dry ECG patch with experimental data on a human subject.
2020 IEEE 17th India Council International Conference (INDICON)
An accurate auto-tunable quadrature-phase generator circuit based on phase-sensitive-detection an... more An accurate auto-tunable quadrature-phase generator circuit based on phase-sensitive-detection and auto-nulling feedback loop for capacitive and impedance sensors is presented in this paper. The core of the phase-generator circuit consists of an operational amplifier based modified all-pass filter circuit with a voltage controlled resistor. The phase-shift of the modified all-pass circuit is compared with the input signal using phase-sensitive-detection technique and, accordingly the auto-nulling loop controls the value of the voltage controlled resistor to maintain a quadrature-phase shift. A prototype of the circuit is designed and experimentally tested by varying the frequency of the input signal from 600 Hz to 1.4 kHz. The circuit shows excellent accuracy with a maximum phase-error within 1 degree. The efficacy of the circuit is further tested with for measuring the capacitance of the impedance R-C sensors.
2020 IEEE International Conference on Flexible and Printable Sensors and Systems (FLEPS), 2020
In this paper a simple and low-cost 3D printed robotic finger is presented. The 3D printed finger... more In this paper a simple and low-cost 3D printed robotic finger is presented. The 3D printed finger is embedded with a low-cost flexible piezoresistive polymer for sensing pressure and a thread-based carbon coated strain sensor for tracking the bending of the finger. The fingers are 3D printed with fused deposition modeling (FDM) printers using polymer composites thereby enabling low cost, high speed and simplicity. Design of a single such 3D printed finger is discussed and results are shown for the embedded pressure and strain sensors using a simple highly linear analog readout circuit.
Respiration is a key vital sign indicative of an individual's health. Current approaches of r... more 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 graphi...
This work presents the development of a robotic hand using 3D printing technology for robotic and... more This work presents the development of a robotic hand using 3D printing technology for robotic and prosthetic applications. The 3D printed hand presented herein is very cost-effective and involves elementary fabrication steps paving the way for rapid manufacturing at low cost. Fused deposition modeling (FDM) printers using polymer composites are used to print with optimized manufacturing settings to achieve a truly low-cost solution through minimal waste, minimal material requirement while achieving the required durability. Further, the 3D printed hand is embedded with pressure and strain sensors for tactile feedback required for human-like dexterity. A piezoresistive polymer-based flexible pressure sensor and an in-house carbon-coated elastic thread-based strain sensor are employed to realize the cost-effective 3D printed hand with tactile feedback. The sensors employed need a highly linear readout circuit for the effective implementation of the tactile feedback. Owing to this, a hi...
2020 IEEE International Conference on Flexible and Printable Sensors and Systems (FLEPS)
A simple, low cost, screen-printed flexible capacitive sensor for moisture, and water level detec... more A simple, low cost, screen-printed flexible capacitive sensor for moisture, and water level detection is presented in this paper. The sensor is fabricated on the flexible polyamide substrate. The interdigitated structure electrodes are screen printed on the substrate to form the capacitive fingers using carbon paste. The relative permittivity of the medium changes due to the water vapors on the sensor, which in turn changes the capacitance of the sensor due to the fringing field. A novel auto-nulling based signal conditioning circuit was utilized to measure the capacitance of the sensor. The flexible nature of the sensor enhances the use of the fabricated capacitive sensor in applications such as diaper wetness monitoring, soil moisture monitoring, body hydration monitoring.
An accurate auto-tunable quadrature-phase generator circuit based on phase-sensitive-detection an... more An accurate auto-tunable quadrature-phase generator circuit based on phase-sensitive-detection and auto-nulling feedback loop for capacitive and impedance sensors is presented in this paper. The core of the phase-generator circuit consists of an operational amplifier based modified all-pass filter circuit with a voltage controlled resistor. The phase-shift of the modified all-pass circuit is compared with the input signal using phase-sensitive-detection technique and, accordingly the auto-nulling loop controls the value of the voltage controlled resistor to maintain a quadrature-phase shift. A prototype of the circuit is designed and experimentally tested by varying the frequency of the input signal from 600 Hz to 1.4 kHz. The circuit shows excellent accuracy with a maximum phase-error within 1 degree. The efficacy of the circuit is further tested with for measuring the capacitance of the impedance R-C sensors.
Sensor platforms that exploit the fibrous textile threads as substrates offer great promise since... more Sensor platforms that exploit the fibrous textile threads as substrates offer great promise since they can be directly sewn, woven or stitched on to any clothing. They can also be placed directly in intimate contact with the skin. In this work, we present a thread-based sensing platform in the form of a multiplexed sensing patch for continuous simultaneous on-skin monitoring of sweat. The patch performs real-time, on-body measurements of important biomarkers present in sweat such as electrolytes (sodium and ammonium ions), metabolites (lactate) and acidity (pH). Flexible threads coated with conductive inks were used as sensing electrodes. Selective potentiometric detection of electrolytes and pH was made possible through ion-selective membrane deposition and pH-sensitive polyaniline coating on threads, respectively. An amperometric enzymatic sensing scheme with lactate oxidase was used for the detection of lactate. An array of the thread sensors is integrated onto a patch with conne...
Most of the resistive sensors have a large baseline resistor and a relatively small incremental c... more 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 <inline-formula> <tex-math notation="LaTeX">$\Delta R/R_{s}$ </tex-math></inline-formula> 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 <inline-formula> <tex-math notation="LaTeX">$\Delta R/R_{s}$ </tex-math></inline-formula> 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 <inline-formula> <tex-math notation="LaTeX">$\Delta R/R_{s}$ </tex-math></inline-formula> for the base resistor <inline-formula> <tex-math notation="LaTeX">$R_{s}$ </tex-math></inline-formula> value as high as 0.5 <inline-formula> <tex-math notation="LaTeX">$\text{M}\Omega $ </tex-math></inline-formula> 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.
IEEE Transactions on Instrumentation and Measurement
In this article, we propose an autonulling-based multimode impedance-to-voltage converter (AN-Z2V... more In this article, we propose an autonulling-based multimode impedance-to-voltage converter (AN-Z2V) signal conditioning circuit for resistive–capacitive (R-C) sensors. The proposed technique takes advantage of the reuse of the phase tracking and autonulling modules to extract the in-phase and quadrature components of the sensors. The circuit is designed for three sensing modes: 1) Mode-C for capacitive sensors with leakage resistor; 2) Mode-R for resistive sensors with parasitic shunt capacitor; and 3) Mode-Z for impedance R-C sensor. A novel autotuning quadrature phase generator circuit is designed and implemented for the generation of reference 90° phase-shifted signal for the leaky capacitive sensors. A prototype of the proposed circuit is fabricated and tested. Measurement results show that AN-Z2V provides the measurement range with low relative error compared with the reported systems. The system is tested for a range of 10–760 pF and 56 <inline-formula> <tex-math notation="LaTeX">$\text{k}\Omega $ </tex-math></inline-formula>–6.5 <inline-formula> <tex-math notation="LaTeX">$\text{M}\Omega $ </tex-math></inline-formula> for mode-C and mode-R, respectively. The accuracy of the proposed circuit is found to be ±0.11% and ±0.07% for mode-C and mode-R, respectively. The capacitance and resistance of the impedance R-C sensor are simultaneously measured in mode-Z for a range of 33–528 pF and 100 <inline-formula> <tex-math notation="LaTeX">$\text{k}\Omega $ </tex-math></inline-formula>–7.8 <inline-formula> <tex-math notation="LaTeX">$\text{M}\Omega $ </tex-math></inline-formula>, respectively.
This paper presents a fully analog auto-nulling bridge based capacitance-to-voltage (AN-C2V) conv... more 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 $\pm ~0.18\%$ 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.
Capacitive sensors suffer from problems of the parasitic and offset capacitors. Also, in some cap... more 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.
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Papers by Meraj Ahmad