Proposed Temperature Sensor Research Articles

A Controllable DCCS-Based PT Temperature Sensor in High Precision Molecular Spectroscopy Application

In the high precision molecular spectroscopy, the temperature of gas absorption cell is accurately measured. In this paper we discuss the factors affecting the measurement accuracy of temperature sensor employing platinum resistance in a resonant quartz crystal tuning fork (QCTF) detector based wavelength modulation spectroscopy (WMS). A bridge temperature sensor powered by a dual constant current source (DCCS) is proposed. The DCCS was controlled to keep the constant current of 1mA in this work. Furthermore, we used the 3-wire measurements powered by DCCS to eliminate the impact of lead resistances and self heating of the platinum resistance so as to reduce measurement errors. A piecewise linearization model by linear approximation algorithm is employed to evaluate the measurement calibration and increase the measurement accuracy. Detection of trace methane (CH 4 ) was demonstrated using a near infrared distributed feedback diode laser near 1.653 μm and a single pass gas absorption cell with an optical length of 20 cm. An example of the temperature sensor employing Pt100 with 3-wire measurement is developed in the detection of CH 4 with the temperature range from 0°C to 100°C. The controllable DCCS method is demonstrated by the measurement results of the deploying Pt100 sensors. Experimental results show that the accuracy of our proposed temperature sensor is improved in comparison with the conventional platinum resistance thermometer. The measurement accuracy is relatively increased due to employing the piecewise linear approximation model. The results also show good performance for measurement calibration, especially for high temperature region.

Research on Temperature Sensor Using Rhodamine6G Film Coated Microstructure Optical Fiber

Temperature monitoring plays a key role in the kinetics of chemical reaction. In this paper, a sensitive dynamic temperature monitoring sensor based on the rhodamine6G (R6g) film coated anti-resonance fiber (ARF) is proposed. Because of the high thermo-dependent fluorescence intensity of R6g, the ARF coated with R6g film is highly sensitive to the temperature variation, forming the basis of our proposed temperature sensor application. To enhance the temperature monitoring performance and strengthen the florescence intensity, one of the ARF ends spliced a silica ball for reflecting the input signal, and the other end is inserted with two tapered multimode fiber (MMF), acting as bridges for the input of pump light and the output of signal light, respectively. The dual-peak reached the temperature resolution of $3.946\times 10^{-2}\,\,^{\circ }\text{C}$ and $3.991\times 10^{-3}\,\,^{\circ }\text{C}$ with linearity of 0.99914 and 0.99953 respectively. The experiment results show that the output fluorescence and pump light intensity decrease with the increasing temperature. These excellent characteristics demonstrate a highly sensitive dual-peak sensor for temperature calibration with wide potential applications, such as environmental monitoring, mine monitoring and other fields of chemical kinetics.

High-precision strain-insensitive temperature sensor based on an optoelectronic oscillator.

We have proposed and experimentally demonstrated a high-precision and strain-insensitive temperature sensor based on an optoelectronic oscillator (OEO). The oscillation frequency of the OEO is determined by the single passband microwave photonic filter (MPF) by using stimulated Brillouin scattering (SBS). The sensing fiber, which acts as the SBS gain medium, is exposed to temperature variations. The Brillouin frequency shift (BFS) changes along with the temperature. Since the central frequency of the MPF is a function of the BFS, the oscillation frequency of the OEO is varied. Besides, due to the mode competition in the OEO, the influence of the strain is eliminated. Thus, the temperature variations can be estimated through measuring the oscillation frequency. We carry out a proof-to-concept experiment. Temperature sensing with a high sensitivity of 1.00745 MHz/°C is achieved. The maximum measurement error of temperature obtained is within ± 0.5 °C. The proposed scheme has merits of simplicity and compact configuration. In addition, the proposed temperature sensor can realize quasi-distributed measurement by utilizing wavelength division multiplexing (WDM).

A 40 nW CMOS-Based Temperature Sensor with Calibration Free Inaccuracy within ±0.6 °C

In this study, a temperature equivalent voltage signal was obtained by subtracting output voltages received from two individual temperature sensors. These sensors work in the subthreshold region and generate the output voltage signals that are proportional and complementary to the temperature. Over the temperature range of −40 °C to +85 °C without using any calibration method, absolute temperature inaccuracy less than ±0.6 °C was attained from the measurement of five prototypes of the proposed temperature sensor. The implementation was done in a standard 0.18 µm CMOS technology with a total area of 0.0018 mm2. The total power consumption is 40 nW for a supply voltage of 1.2 V measured at room temperature.

On-Chip Smart Temperature Sensors for Dark Current Compensation in CMOS Image Sensors

This paper proposes various types of on-chip smart temperature sensors, intended for thermal compensation of dark current in CMOS image sensors (CIS). It proposes four different architectures of metal–oxide–semiconductor (MOS)-based and bipolar junction transistor (BJT)-based temperature sensors inside and outside the CIS array. Both of the MOS-based temperature sensors make use of the thermal dependence of MOS transistors working in the subthreshold region with ratiometric currents and are quantized by the 14-bit first-order incremental delta–sigma analog-to-digital converters (ADCs). Fabricated using 0.18- $\mu \text{m}$ CIS technology and measured on four chips, the proposed temperature sensors are compared, on their resolution and process variability, as well as on their effects on the neighboring image pixels implemented on the same chip. Experimental results show that the MOS-based temperature sensors inside and outside the array consume a power of 36 and $40~\mu \text{W}$ , respectively, both achieving 3-sigma ( $\sigma$ ) inaccuracy less than ±0.75 °C on four different chips, over a temperature range from −20°C to 80 °C at a conversion time of 16 ms. The temperature sensors facilitate the digital thermal compensation of dark current in the CIS array, by at least 80%, in experiments.

All‐MOS self‐referenced temperature sensor

This Letter presents an all-MOS self-referenced temperature sensor, intended for thermal compensation of dark current in CMOS image sensors (CIS). Its thermal sensing front-end is based on a self-biased nMOS pair working in the subthreshold region. Biased with ratiometric currents, the differential voltage output of the nMOS pair is proportional to the absolute temperature. The thermal sensing voltage is quantised by a self-referenced first-order incremental delta–sigma ADC, which obtains its reference voltage from the thermal sensing front-end. This reference voltage has been virtually attenuated, through switch capacitor charge sampling, to improve the resolution of the temperature sensor. Measured between −20 and 80°C, the proposed temperature sensor achieves an inaccuracy within ±0.55°C.

A portable optical fiber SPR temperature sensor based on a smart-phone.

In this paper, a fiber-optic temperature sensing system, based on surface plasmon resonance (SPR) and integrated with a smart-phone platform, is proposed and demonstrated. The sensing system is composed of a side-polished-fiber-based SPR sensor, which is illuminated by the LED flash from one end, and the output signals are recorded and processed by the camera and a designed application in the smart-phone. The sensing performance is evaluated by immersing the sensor in distilled water under different temperatures. Experimental results show that the measurement resolution of the proposed temperature sensor can reach 0.83°C in the range from 30 to 70°C, corresponding to a linear correlation coefficient of 0.9798. The low-cost and portable fiber optic SPR sensor based on a smart-phone platform has wide application potentials in the fields of health-care, environmental monitoring, etc.

High-sensitivity plasmonic temperature sensor based on gold-coated D-shaped photonic crystal fiber.

A high-sensitivity temperature sensor based on gold-coated D-shaped photonic crystal fiber is proposed in this paper. To enhance the sensing performances, gold as the surface plasmon resonance material is coated on the polishing surface. The thermosensitive liquid consists of ethanol and chloroform, and it is placed on the outer layer of the photonic crystal fiber. As the phase-matching condition is satisfied, the core mode couples to the surface plasmon polariton mode, and energy transfer occurs. The influences of the structural parameters on the sensing characteristics were studied using the finite element method. The numerical results show the average sensitivity can reach up to 10.61 nm/°C, and the linearity R2=0.99341 for the temperature sensing ranges of 0-60°C. Moreover, a good spectral shape can be realized by the proposed fiber. Compared with some previously reported temperature sensors, the proposed temperature sensor shows excellent performances in terms of the sensitivity, detection range, and fabrication.

A CMOS-Imager-Pixel-Based Temperature Sensor for Dark Current Compensation

This brief proposes employing each of the classical 4 transistor (4T) pinned photodiode (PPD) CMOS image sensor (CIS) pixels, for both imaging and temperature measurement, intended for compensating the CISs’ dark current, and dark signal non-uniformity (DSNU). The proposed temperature sensors rely on the thermal behavior of MOSFETs working in subthreshold region, when biased with ratiometric currents sequentially. Without incurring any additional hardware or penalty to the CIS, they are measured to have thermal curvature errors less than ±0.3 °C and $3~\sigma $ process variations within ±1.3 °C, from 108 sensors on 4 chips, over a temperature range from −20 °C to 80 °C. Each of them consumes 576 nJ/conversion at a conversion rate of 62 samples/s, when quantized by 1st-order 14 bit delta–sigma ADCs and fabricated using $0.18~\mu \text{m}$ CIS technology. Experimental results show that they facilitate digital compensation for average dark current and DSNU by 78% and 20%, respectively.

An 11-nW CMOS Temperature-to-Digital Converter Utilizing Sub-Threshold Current at Sub-Thermal Drain Voltage

A fully integrated CMOS temperature-to-digital converter utilizing MOSFETs in the sub-threshold region is proposed. The temperature-to-digital converter achieves the ultra-low power operation required for Internet of Things (IoT) nodes. The proposed principle takes the ratio of the sub-threshold currents of two nMOSFETs whose drain voltages are maintained well above and well below the thermal voltage, respectively. The proposed circuit implementation of the temperature-to-digital converter achieves ultra-low power consumption of 11 nW at room temperature of 25 °C. Measurement results of the proposed temperature sensor fabricated in a 180-nm CMOS process show −0.9/+1.2 °C peak-to-peak inaccuracy over a temperature range of −20 °C to 80 °C after a two-point calibration while achieving a resolution of 145 mK.

Tunable temperature sensor based on an integrated plasmonic grating

Plasmonic grating sensors, which can achieve ultrafast response and real-time sample detection, as well as mitigate the electromagnetic interference, is a major research area in nanooptical sensors. In this article, we propose an integrated temperature/refractive sensor based on a plasmonic periodic grating with resonance peaks that can be tuned by the structural parameters. It is composed of optical fiber substrate, InGaAsP semiconductor material, Ag periodic grating, and surface monolayer graphene from bottom to top and the temperature sensing solution is filled on the top of the grating. According to quantitative analysis, the structural parameters, and the reflectance spectrum, the sensitivity of the proposed temperature sensor can reach 0.455 nm/°C or 1625 nmRIU−1. In addition, the operating wavelength can be tuned by structural parameters in the optical communication wavelengths; as a result, the application in integrated optical fiber sensing and biological measurements can be broadened.

A CMOS Temperature Sensor With Versatile Readout Scheme and High Accuracy for Multi-Sensor Systems

In this paper, a smart CMOS temperature sensor with a versatile readout scheme is presented. A digital-assisted readout solution is proposed to improve the compatibility of the circuit and maintain the performance of a traditional smart temperature sensor. In addition, the potential multi-operating points of the analog front-end are analyzed, and a compact start-up circuit is designed to make the analog front-end work properly. Fabricated in a standard 0.13 $\mu \text{m}$ CMOS process, the proposed temperature sensor occupies a silicon area of 0.29 mm2 and draws a current of $95~\mu \text{A}$ from a 2 to 3.6 V supply voltage at the room temperature. Measured results show that the proposed design has the inaccuracy of ± 0.47 °C ( $3\sigma $ ) from −40 °C to 125 °C after a single-point temperature calibration. It achieves a resolution of 16 mK at a conversion time of 5.12 ms and a supply sensitivity of less than 0.05 °C/V. Thanks to the versatile readout scheme, the proposed temperature sensor is compatible with multi-sensor systems where the readout-circuitry can be shared between different input signals.

A 0.6 V 117 nW high performance energy efficient system-on-chip (SoC) CMOS temperature sensor in 0.18 µm CMOS for aerospace applications

This research article presents and describes a novel design with improved performance low power consumption threshold voltage based CMOS thermal sensor for aerospace applications. The proposed temperature sensor utilizes the change in behavior of threshold voltage of MOSFET with variation in temperature. The challenge while designing the temperature sensor was to achieve the linearize output voltage with respect to change in temperature. Process corner analysis has been done to check the robustness of the circuit while performance analysis and sensitivity of the temperature sensor have been verified in the occurrence of parasitic. The proposed temperature sensor is featured with low power consumption, less power supply voltage utilization, high performance and sensitivity with inaccuracy as low as possible. The presented temperature sensor utilizes an active area of 18 µm × 9.85 µm with 117 nW power consumption. An improved linear performance with an inaccuracy of merely − 0.01 to + 0.47 °C over a wide temperature range of − 20 to + 120 °C is presented here. The sensitivity of proposed temperature sensor is found to be as high as 0.77 mV/°C. The proposed temperature sensor is realized and tested in Cadence virtuoso mixed signal design atmosphere using 0.18 µm CMOS technology and further investigated with support of tool from Mentor graphics. The engaged area of pad-limited chip is measured to be 0.96 mm2.

A microfiber temperature sensor based on fluorescence lifetime

We demonstrate micro/nanofiber temperature sensors based on micro/nano particles fluorescence lifetime. Dependence of the fluorescence intensity, branching ratio and lifetime on temperature are investigated from 30°to 210°. Compared with the intensity-based micro sensors, the lifetime-based micro sensors perform better in terms of accuracy, stability, and response speed. Precision of the proposed temperature sensor is obtained as high as 2°in the temperature range of 30°to 210°. This lifetime-based sensing technology won‘t be affected by external deformation of the sensors, proving it is a temperature selective sensor enabling eliminating interference of surrounding environment and background noise. Experiments and simulations show that response time of the micro sensor can be 50–100 times faster than that of conventional sensors.

Applied microfiber evanescent wave on ZnO nanorods coated glass surface towards temperature sensing

A temperature sensor fabricated by using silica microfiber laid on glass surface coated with Zinc Oxide (ZnO) nanorods is reported. The silica microfiber was tapered for waist of 5 μm using flame brushing technique. The glass surface was grown with ZnO nanorods using hydrothermal method. A significant response to temperature changes from 40 °C to 120 °C was observed due to the change of ZnO refractive index on the glass surface resulting different light attenuation in the silica microfiber. Sensitivity increases by a factor of 3.1 in microfiber laid on the coated glass surface as compared to uncoated glass surface. As the temperature increases, the output power of the ZnO nanorods coated glass surface has decreasing linearly from −19.8 dB m to −23.32 dB m with linearity and resolution of 99.8% and 1.75 °C respectively. The proposed temperature sensor employs the dispersion of evanescent wave from silica microfiber and glass surface coated with ZnO nanorods which is easier to handle during synthesis process and sensing applications.

CMOS Temperature Sensor with Programmable Temperature Range for Biomedical Applications

<div class="page" title="Page 1"><div class="layoutArea"><div class="column"><p class="p1"><span class="s1">A CMOS temperature sensor circuit with programmable temperature range is proposed for biomedical applications. The proposed circuit consists of temperature sensor core circuit and programmable temperature range digital interface circuit. Both circuits are able to be operated at 1.0 V. The proposed temperature sensor circuit is operated in weak inversion region of MOSFETs. The proposed digital interface circuit converts current into time using Current-to-Time Converter (ITC) and converts time to digital data using counter. Temperature range can be programmed by adjusting pulse width of the trigger and clock frequency of counter. The proposed circuit was simulated using HSPICE with 1P, 5M, 3-wells, 0.18-μm CMOS process (BSIM3v3.2, LEVEL53). From the simulation of proposed circuit, temperature range is programmed to be 0 °C to 100 °C, it is obtained that resolution of the proposed circuit is 0.392 °C with -0.89/+0.29 °C inaccuracy and the total power consumption is 22.3 μW in 25 °C.<span class="Apple-converted-space"> </span></span></p></div></div></div>

A 1.2V Self-Referenced Temperature Sensor With a Time-Domain Readout and a Two-Step Improvement on Output Dynamic Range

A self-referenced temperature sensor with a time-domain readout and a two-step improvement on output dynamic range is presented in this paper. The proposed temperature sensor utilizes BJTs to generate temperature dependent/independent currents, which are converted to digital bits using a ring-oscillator-based time-domain readout scheme. A novel two-step improvement on output dynamic range is proposed to improve the power-efficiency and simplify the hardware design with a high conversion rate. Furthermore, the adopted process compensation strategy and the self-referenced readout scheme make the whole temperature sensor robust to process and supply variations. Fabricated in a standard 0.13- $\mu \text{m}$ CMOS process, the proposed temperature sensor occupies a die area of 0.06 mm2 and consumes 9.92 nJ per conversion at a conversion rate of 75 kSa/s. After one-point calibration at 20 °C, the sensor achieves inaccuracies of −2.88 °C/+2.71 °C and −1.7 °C/1.36 °C from −20 °C to 100 °C, with and without systematic nonlinearity removal, respectively. It shows an average supply sensitivity of 0.0136 °C/mV from 1.05 V to 1.4 V without any external reference clock or voltage regulators.

Detection and localization of changes in two-dimensional temperature distributions by electrical resistance tomography

This paper studies the feasibility of applying electrical resistance tomography (ERT) to detect changes in two-dimensional (2D) temperature distributions with potential applications in sensor development. The proposed sensor consists of a thin layer of porous metal film manufactured by spraying colloidal copper paint to a solid surface. A change of the temperature distribution on the surface changes the 2D distributed electrical conductivity of the metal film. The change of the electrical conductivity is localized and quantified with ERT, and further, to convert the estimated conductivity change of the sensor to temperature change, an experimentally developed model is used. The proposed temperature sensor is evaluated experimentally by applying it to a polymeric substrate, and exposing it to known temperature changes using heat sources of different shapes. The results demonstrate that the proposed sensor is capable of detecting and localizing temperature changes, and provides at least qualitative information on the magnitude of the temperature change.

An ultra-low power high-performance CMOS temperature sensor with an inaccuracy of − 0.3 °C/ + 0.1 °C for aerospace applications

In the current paper, a new temperature sensor with improved temperature inaccuracy and with very low power consumption has been designed for avionic industry. The temperature sensor is specifically designed so that it possesses features like low power consumption, high sensitivity, and least possible inaccuracy. Sensitivity and performance analysis of the sensor has been done in the presence of parasitic. Analysis at each step with variations at different parameters has also been done to verify the robustness of the circuit. The temperature sensor utilizes the device characteristics with the threshold voltage. The temperature coefficient at 1 V power supply is quite low which makes it possible for the transistors to work in the sub-threshold region or cutoff region. A linear plot is exhibited in such region and to use this property of CMOS technology in the circuit design, it has opted here. The designed temperature sensor exhibited better results in terms of linearity, power consumption and error when compared to previously designed temperature sensors. The proposed temperature sensor covers an area of 24.8 μm × 22.4 μm and consumes power as low as 45 nW. A highly linear performance with an error of mere − 0.3 to + 0.1 °C within the range of − 55 to + 155 °C is reported. The temperature sensor has been tested at 1 V and the simulation has been carried out with the help of cadence analog design environment with UMC 90 nm technology.

Surface-plasmon-resonance-based optical-fiber temperature sensor with high sensitivity and high figure of merit

We propose and demonstrate a novel and compact optical-fiber temperature sensor with a high sensitivity and high figure of merit (FOM) based on surface plasmon resonance (SPR). The sensor is fabricated by employing a single-mode twin-core fiber (TCF), which is polished as a circular truncated cone and coated with a layer of gold film and a layer of polydimethylsiloxane (PDMS). Owing to the high refractive index sensitivity of SPR sensors and high thermo-optic coefficient of PDMS, the sensor realizes a high temperature sensitivity of -4.13 nm/°C to -2.07 nm/°C in the range from 20°C to 70°C, transcending most other types of optical-fiber temperature sensors. Owing to the fundamental mode beam transmitting in the TCF, the sensor realizes a high FOM of up to 0.034/°C, more than twice that of SPR sensors based on multimode fiber. The proposed temperature sensor is meaningful and will have potential applications in many fields, such as biomedical and biomaterial.