A 7 μW Offset- and Temperature-Compensated pH-to-Digital Converter

This paper demonstrates a micropower offset- and temperature-compensated smart pH sensor, intended for use in battery-powered RFID systems that monitor the quality of perishable products. Low operation power is essential in such systems to enable autonomous logging of environmental parameters, such as the pH level, over extended periods of time using only a small, low-cost battery. The pH-sensing element in this work is an ion-sensitive extended-gate field-effect transistor (EGFET), which is incorporated in a low-power sensor front-end. The front-end outputs a pH-dependent voltage, which is then digitized by means of a co-integrated incremental delta-sigma ADC. To compensate for the offset and temperature cross-sensitivity of the EGFET, a compensation scheme using a calibration process and a temperature sensor has been devised. A prototype chip has been realized in a 0.16 μm CMOS process. It occupies 0.35 × 3.9 mm2 of die area and draws only 4 μA from a 1.8 V supply. Two different types of custom packaging have been used for measurement purposes. The pH sensor achieves a linearity of better than ±0.1 for pH values ranging from 4 to 10. The calibration and compensation scheme reduces errors due to temperature cross-sensitivity to less than ±0.1 in the temperature range of 6°C to 25°C.

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A Low-Cost Low-Power Capacitive Humidity Sensor in CMOS Technology

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.556-562.1842 ◽

2014 ◽

Vol 556-562 ◽

pp. 1842-1846

Author(s):

Fang Ming Deng ◽

Yi Gang He

Keyword(s):

Humidity Sensor ◽

Supply Voltage ◽

Low Cost ◽

Cmos Technology ◽

Cmos Process ◽

Sensing Element ◽

Digital Conversion ◽

Sensor Interface ◽

Delta Sigma ◽

Capacitive Humidity Sensor

This paper presents a capacitive humidity sensor in CMOS technology. The humidity sensor element is implemented in standard CMOS technology without any further post-processing, which results in low fabrication cost. The sensor interface is based on a delta-sigma converter and can be easily reconfigured to compensate for process variation of the sensing element. The proposed humidity sensor is fabricated in 0.16μm standard CMOS process and the chip occupies 0.25mm2. The measurement result shows that this humidity sensor acquires a resolution of 0.1%RH in the range of 20%RH to 90%RH. The interface achieves a 12.5-bits capacitance-to-digital conversion and consumes only 9.6μW power at 1.2V supply voltage.

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Ruthenium Oxide pH Sensing for Organs-On-Chip Studies

Proceedings ◽

10.3390/proceedings2130709 ◽

2018 ◽

Vol 2 (13) ◽

pp. 709 ◽

Cited By ~ 2

Author(s):

Esther Tanumihardja ◽

Wouter Olthuis ◽

Albert van den Berg

Keyword(s):

Ph Sensor ◽

Ruthenium Oxide ◽

Open Circuit ◽

Biological Medium ◽

Similar Response ◽

Ph Sensing ◽

Ph Sensors ◽

Cross Sensitivity ◽

On Chip

A ruthenium oxide (RuOx) electrode is being developed as potentiometric pH sensor for organs-on-chip applications. Open-circuit potential (OCP) of the RuOx electrode showed a response of −58.05 mV/pH, with no cross-sensitivity to potentially interfering/complexing ions (tested were lithium, sulfate, chloride, and calcium ions). Similar response was observed in complex biological medium. The electrode stored in liquid had a long-term drift of −0.8 mV/hour (corresponding to ΔpH of 0.013/hour) and response time in complex biological medium was 3.7 s. Minimum cross-sensitivity to oxygen was observed as the OCP shifted ~3 mV going from deoxygenated to oxygenated solution. This response is one magnitude lower than previously reported for metal- oxide pH sensors. Overall, the RuOx pH sensor has proven to be a suitable pH sensor for organs- on-chip applications.

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Electropolymerised pH Insensitive Salicylic Acid Reference Systems: Utilization in a Novel pH Sensor for Food and Environmental Monitoring

Sensors ◽

10.3390/s22020555 ◽

2022 ◽

Vol 22 (2) ◽

pp. 555

Author(s):

Monica Miranda Mugica ◽

Kay Louise McGuinness ◽

Nathan Scott Lawrence

Keyword(s):

Cell Culture ◽

Salicylic Acid ◽

Reference System ◽

Culture Media ◽

Ph Sensor ◽

Active Species ◽

Ph Sensing ◽

Sensing Element ◽

Electrochemical Response ◽

Local Ph

This work summarizes the electrochemical response of a salicylic acid-based carbon electrode for use as a novel solid-state reference electrode in a redox-based pH sensor. This novel reference produces a pH insensitive response over a range of pH 3–10 in solutions with low buffer concentrations, different compositions, conductivities, and ionic strengths is produced. The pH of the local environment is shown to be determined by the chemistry and the electrochemical response of the redox active species on the surface of the electrode; the local pH can be controlled by the electropolymerized salicylic acid moieties due to the acid concentration on the surface, avoiding any perturbation in environmental pH and leading to a stable novel reference system. Sensitivities of −7.1 mV/pH unit, −2.4 mV/pH unit, −0.2 mV/pH unit, and 2.5 mV/pH units were obtained for different food medias, hydroponic solution, seawater, and cell-culture media, respectively, confirming its ability to control the local pH of the electrode. This reference system is paired with a new pH sensing element based on electropolymerized flavanone to provide a calibration free, pH sensitive sensor to effectively and accurately measure the pH of various media with high viscosity, low conductivity, low/high buffer concentration or cell-culture environment, presenting a maximum error of +/−0.03 pH units.

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A 10-Gb/s 0.18-μm CMOS Optical Receiver Front-End Amplifier

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.760-762.115 ◽

2013 ◽

Vol 760-762 ◽

pp. 115-119

Author(s):

Wen Yuan Li ◽

Rui Guo

Keyword(s):

Low Voltage ◽

Low Cost ◽

Parasitic Capacitance ◽

Optical Receiver ◽

Cmos Process ◽

Chip Area ◽

Noise Interference ◽

Limiting Amplifier ◽

Front End ◽

Voltage Swing

A fully integrated 10-Gb/s optical receiver analog front-end (AFE) design that includes a transimpedance amplifier (TIA) and a limiting amplifier (LA) is demonstrated to require less chip area and is suitable for both low-cost and low-voltage applications. The AFE is stimulation using a 0.18μm CMOS process. In order to avoid off-chip noise interference, the TIA and LA are dc-coupled on the chip instead of ac-coupled though a large external capacitor. The tiny photo current received by the receiver AFE is amplified to voltage swing of 400. The results indicate that, with a photodiode parasitic capacitance of 500fF and the bonding pad parasitic capacitance of 200fF between which a 2-mm bond wire is inserted at the input node, the AFE provides a conversion gain of up to 89.21 dB and 3 dB bandwidth of 9.78 GHz. Operating under a 1.8V supply, circuit power dissipation is 95 mW and its sensitivity is 18.5μA for BER of 10-12

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Low Cost Detection of pH and its Effect on the Capacitive Behavior of Micro-Gap Sensor

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.832.73 ◽

2013 ◽

Vol 832 ◽

pp. 73-78 ◽

Cited By ~ 1

Author(s):

Q. Humayun ◽

U. Hashim ◽

Tijjani Adam

Keyword(s):

Ph Value ◽

Low Cost ◽

Ph Sensor ◽

Pattern Transfer ◽

Ph Sensing ◽

Sensor Structure ◽

Gap Spacing ◽

Photolithography Process ◽

Electrical Data

The article describes the fabrication and characterization of silver microgap sensor on silicon substrate. By employing cheap photolithography process the proposed microgap sensor has been fabricated. The silver microgap sensor was used for pH sensing, by dropping different pH on microgap surface. To obtain the microgap sensor structure by using AutoCAD software, mask was designed. To maintain high accuracy in pattern transfer the AutoCAD design mask was transferred to chrome glass mask. The fabricated silver microgap pH sensor gap spacing was around 03μm. From the electrical data we conclude that when the pH value varies from acidic to basic (pH 1, pH 2 to pH 11, pH 13) the value of capacitance decreased from 33pF to 8pF. The result shows that the silver microgap pH sensor has the ability to differentiate the acidic pH form basic one. The next part of the research is to decrease the microgap spacing until reach to nanosize spacing, so that can easily used for biosensing application.

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Titanium Nitride Thin Film Based Low-Redox-Interference Potentiometric pH Sensing Electrodes

Sensors ◽

10.3390/s21010042 ◽

2020 ◽

Vol 21 (1) ◽

pp. 42

Author(s):

Shimrith Paul Shylendra ◽

Wade Lonsdale ◽

Magdalena Wajrak ◽

Mohammad Nur-E-Alam ◽

Kamal Alameh

Keyword(s):

Thin Film ◽

Titanium Nitride ◽

Orange Juice ◽

Ph Sensor ◽

Reference Electrode ◽

Cost Effective ◽

Ph Sensing ◽

Ph Sensors ◽

Potential Shift ◽

Double Junction

In this work, a solid-state potentiometric pH sensor is designed by incorporating a thin film of Radio Frequency Magnetron Sputtered (RFMS) Titanium Nitride (TiN) working electrode and a commercial Ag|AgCl|KCl double junction reference electrode. The sensor shows a linear pH slope of −59.1 mV/pH, R2 = 0.9997, a hysteresis as low as 1.2 mV, and drift below 3.9 mV/h. In addition, the redox interference performance of TiN electrodes is compared with that of Iridium Oxide (IrO2) counterparts. Experimental results show −32 mV potential shift (E0 value) in 1 mM ascorbic acid (reducing agent) for TiN electrodes, and this is significantly lower than the −114 mV potential shift of IrO2 electrodes with sub-Nernstian sensitivity. These results are most encouraging and pave the way towards the development of miniaturized, cost-effective, and robust pH sensors for difficult matrices, such as wine and fresh orange juice.

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60–700 K CTAT and PTAT Temperature Sensors with 4H-SiC Schottky Diodes

Sensors ◽

10.3390/s21030942 ◽

2021 ◽

Vol 21 (3) ◽

pp. 942

Author(s):

Razvan Pascu ◽

Gheorghe Pristavu ◽

Gheorghe Brezeanu ◽

Florin Draghici ◽

Philippe Godignon ◽

...

Keyword(s):

Low Cost ◽

Schottky Diodes ◽

Schottky Contact ◽

High Sensitivity ◽

Xrd Analysis ◽

Absolute Temperature ◽

Lower Sensitivity ◽

Readout Circuit ◽

Sensing Element ◽

High Performing

A SiC Schottky dual-diode temperature-sensing element, suitable for both complementary variation of VF with absolute temperature (CTAT) and differential proportional to absolute temperature (PTAT) sensors, is demonstrated over 60–700 K, currently the widest range reported. The structure’s layout places the two identical diodes in close, symmetrical proximity. A stable and high-barrier Schottky contact based on Ni, annealed at 750 °C, is used. XRD analysis evinced the even distribution of Ni2Si over the entire Schottky contact area. Forward measurements in the 60–700 K range indicate nearly identical characteristics for the dual-diodes, with only minor inhomogeneity. Our parallel diode (p-diode) model is used to parameterize experimental curves and evaluate sensing performances over this far-reaching domain. High sensitivity, upwards of 2.32 mV/K, is obtained, with satisfactory linearity (R2 reaching 99.80%) for the CTAT sensor, even down to 60 K. The PTAT differential version boasts increased linearity, up to 99.95%. The lower sensitivity is, in this case, compensated by using a high-performing, low-cost readout circuit, leading to a peak 14.91 mV/K, without influencing linearity.

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Turning Base Transceiver Stations into Scalable and Controllable DC Microgrids Based on a Smart Sensing Strategy

Sensors ◽

10.3390/s21041202 ◽

2021 ◽

Vol 21 (4) ◽

pp. 1202

Author(s):

Miguel Tradacete ◽

Carlos Santos ◽

José A. Jiménez ◽

Fco Javier Rodríguez ◽

Pedro Martín ◽

...

Keyword(s):

Electricity Market ◽

Low Cost ◽

Storage System ◽

Environmental Parameters ◽

Weather Conditions ◽

Energy Storage System ◽

Electricity Grid ◽

Dc Microgrids ◽

Smart Sensing ◽

Battery Energy

This paper describes a practical approach to the transformation of Base Transceiver Stations (BTSs) into scalable and controllable DC Microgrids in which an energy management system (EMS) is developed to maximize the economic benefit. The EMS strategy focuses on efficiently managing a Battery Energy Storage System (BESS) along with photovoltaic (PV) energy generation, and non-critical load-shedding. The EMS collects data such as real-time energy consumption and generation, and environmental parameters such as temperature, wind speed and irradiance, using a smart sensing strategy whereby measurements can be recorded and computing can be performed both locally and in the cloud. Within the Spanish electricity market and applying a two-tariff pricing, annual savings per installed battery power of 16.8 euros/kW are achieved. The system has the advantage that it can be applied to both new and existing installations, providing a two-way connection to the electricity grid, PV generation, smart measurement systems and the necessary management software. All these functions are integrated in a flexible and low cost HW/SW architecture. Finally, the whole system is validated through real tests carried out on a pilot plant and under different weather conditions.

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A Fast Lock All-Digital MDLL Using a Cyclic Vernier TDC for Burst-Mode Links

Electronics ◽

10.3390/electronics10020177 ◽

2021 ◽

Vol 10 (2) ◽

pp. 177

Author(s):

Dongjun Park ◽

Sungwook Choi ◽

Jongsun Kim

Keyword(s):

Sampling Technique ◽

Cmos Process ◽

Detection Range ◽

Delay Locked Loop ◽

Delta Sigma Modulator ◽

Correlated Double Sampling ◽

Delta Sigma ◽

Fast Power ◽

Low Jitter ◽

Reference Clock

An all-digital multiplying delay-locked loop (MDLL)-based clock multiplier featuring a time-to-digital converter (TDC) to achieve fast power-on capability is presented. The proposed MDLL adopts a new offset-free cyclic Vernier TDC to achieve a fast lock time of 15 reference clock cycles while maintaining a wide detection range and high resolution. The proposed offset-free TDC also uses a correlated double sampling technique to remove mismatch and offset issues, resulting in low jitter characteristics. After the MDLL is quickly locked, the TDC is turned off, and it goes into delta-sigma modulator (DSM)-based sequential tracking mode to reduce power consumption and improve jitter performance. Implemented in a 65-nm 1.0-V CMOS process, the proposed MDLL occupies an active area of 0.043 mm2 and generates a 2.4-GHz output clock from a 75-MHz reference clock (multiplication factor N = 32). It achieves an effective peak-to-peak jitter of 9.4 ps and consumes 3.3 mW at 2.4 GHz.

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Fabrication of Porous Silicon Based Humidity Sensing Elements on Paper

Journal of Sensors ◽

10.1155/2015/927396 ◽

2015 ◽

Vol 2015 ◽

pp. 1-10 ◽

Cited By ~ 12

Author(s):

Tero Jalkanen ◽

Anni Määttänen ◽

Ermei Mäkilä ◽

Jaani Tuura ◽

Martti Kaasalainen ◽

...

Keyword(s):

Porous Silicon ◽

Smart Cities ◽

Low Cost ◽

Electrical Characterization ◽

Fabrication Process ◽

Sensing Element ◽

Paper Substrate ◽

Roll To Roll ◽

Silver Electrodes ◽

Silicon Based

A roll-to-roll compatible fabrication process of porous silicon (pSi) based sensing elements for a real-time humidity monitoring is described. The sensing elements, consisting of printed interdigitated silver electrodes and a spray-coated pSi layer, were fabricated on a coated paper substrate by a two-step process. Capacitive and resistive responses of the sensing elements were examined under different concentrations of humidity. More than a three orders of magnitude reproducible decrease in resistance was measured when the relative humidity (RH) was increased from 0% to 90%. A relatively fast recovery without the need of any refreshing methods was observed with a change in RH. Humidity background signal and hysteresis arising from the paper substrate were dependent on the thickness of sensing pSi layer. Hysteresis in most optimal sensing element setup (a thick pSi layer) was still noticeable but not detrimental for the sensing. In addition to electrical characterization of sensing elements, thermal degradation and moisture adsorption properties of the paper substrate were examined in connection to the fabrication process of the silver electrodes and the moisture sensitivity of the paper. The results pave the way towards the development of low-cost humidity sensors which could be utilized, for example, in smart packaging applications or in smart cities to monitor the environment.

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