Differential Temperature Sensor Research Articles

Quantification of surface layer turbulence using sensible heat values from energy balance versus aerodynamic methods

Surface layer optical turbulence values in the form of the refractive index structure function C n 2 are often calculated from surface layer temperature, moisture, and wind characteristics and compared to measurements from sonic anemometers, differential temperature sensors, and imaging systems. A key derived component needed in the surface layer turbulence calculations is the sensible heat value. Typically, the sensible heat is calculated using the bulk aerodynamic method that assumes a certain surface roughness and a friction velocity that approximates the turbulence drag on temperature and moisture mixing from the change in the average surface layer vertical wind velocity. These assumptions/approximations generally only apply in free convection conditions. To obtain the sensible heat, a more robust method, which applies when free convection conditions are not occurring, is via an energy balance method such as the Bowen ratio method. The use of the Bowen ratio––the ratio of sensible heat flux to latent heat flux––allows a more direct assessment of the optical turbulence-driving surface layer sensible heat flux than do more traditional assessments of surface layer sensible heat flux. This study compares surface layer C n 2 values using sensible heat values from the bulk aerodynamic and energy balance methods to quantifications from sonic anemometers posted at different heights on a sensor tower. The research shows that the sensible heat obtained via the Bowen ratio method provides a simpler, more reliable, and more accurate way to calculate surface layer C n 2 values than what is required to make such calculations from bulk aerodynamic method-obtained sensible heat.

On-Chip Power Monitoring: Leveraging High-Sensitivity Differential Temperature Sensors With Chopper Stabilization and Offset Calibration

On-Chip Power Monitoring: Leveraging High-Sensitivity Differential Temperature Sensors With Chopper Stabilization and Offset Calibration

Aging Compensation in a Class-A High-Frequency Amplifier with DC Temperature Measurements.

One of the threats to nanometric CMOS analog circuit reliability is circuit performance degradation due to transistor aging. To extend circuit operating life, the bias of the main devices within the circuit must be adjusted while the aging degradation process affects them by using a monitor circuit that tracks the evolution of the circuit performance. In this paper, we propose the use of DC temperature measurements in the proximity of the circuit to perform the monitoring of circuit performance degradation and as an observable variable to adjust the bias of the main devices to restore the degraded performance to the original values. To this end, we present experimental results obtained from nine samples of a standard CMOS integrated circuit containing a high-frequency class-A power amplifier and a differential temperature sensor. After accelerated aging, the gain of the amplifier is degraded up to 50%. We propose two different procedures to perform DC temperature measurements that allow tracking of the amplifier gain degradation due to aging and, by uniquely observing temperature readings, automatically set a new bias for the amplifier devices that restores the original amplifier gain. Whereas one of the procedures is able to restore the gain up to a certain limit, the second allows full gain restoration.

Assessing the Performance of Building Mechanical Systems in an Office Building

The purpose of this research is to evaluate the performance of building mechanical systems in an office. The mechanical systems include eleven variable air volume (VAV) units that provide outdoor air to the office spaces and induction units that provide heating and cooling to the office spaces. This study presents the data collection, sensor installation, and analyses of the ventilation, heating, and cooling provided to the spaces. Differential pressure transducers, temperature sensors, and heat flux sensors were installed on-site to monitor these systems at every one-minute and five-minute interval. The process of analyzing datasets from these sensors is automated and used to calculate ventilation, heating, and cooling under current building automation sequences of operation. The results of this study will aid our understanding of the impacts of different building mechanical systems, occupancy patters, time of the day on the ventilation, heating, and cooling use for the selected building.

Highly Sensitive Temperature Sensor Using Low-Temperature Polysilicon Oxide Thin-Film Transistors

We report highly sensitive temperature sensing circuits using low temperature polysilicon oxide (LTPO) thin-film transistors (TFTs) on a glass substrate. The sensor has the LTPO operational amplifier (Op-Amp) made of dual gate (DG) amorphous InGaZnO (a-IGZO) and low temperature poly-Si (LTPS) TFTs by blue laser annealing process. The DG a-IGZO TFTs-based sensing circuit exhibits a sensitivity of 37.9±3 mV/°C and it can be further boosted to 223.33±8 mV/°C by incorporating LTPO Op-Amp for body temperature detection (35~40 °C). The DG a-IGZO TFT exhibits robust threshold voltage stability ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Delta {\rm V}_{Th}$ </tex-math></inline-formula> = −0.16 V) with temperature, which is essential for the practical development of the proposed LTPO differential temperature sensor (TS) to accurately measure the human body temperature.

Re-Visiting Acoustic Sounding to Advance the Measurement of Optical Turbulence

Optical turbulence, as determined by the widely accepted practice of profiling the temperature structure constant, CT2, via the measurement of ambient atmospheric temperature gradients, can be found to differ quite significantly when characterizing such gradients via thermal-couple differential temperature sensors as compared to doing so with acoustic probes such as those commonly used in sonic anemometry. Similar inconsistencies are observed when comparing optical turbulence strength derived via CT2 as compared to those through direct optical or imaging measurements of small fluctuations of the index of refraction of air (i.e., scintillation). These irregularities are especially apparent in stable atmospheric layers and during diurnal quiescent periods. Our research demonstrates that when care is taken to properly remove large-scale index of refraction gradients, the sonic anemometer-derived velocity structure constant, Cv2, coupled with the similarly derived turbulence-driven index of refraction and vertical wind shear gradients, provides a refractive index structure constant, Cn2, that can more closely match the optical turbulence strengths inferred by more direct means such as scintillometers or differential image motion techniques. The research also illustrates the utility and robustness of quantifying Cn2 from CT2 at a point using a single sonic anemometer and establishes a clear set of equations to calculate volumetric Cn2 data using instrumentation that measures wind velocities with more spatial/temporal fidelity than temperature.

Temperature Difference Sensor to Monitor the Temperature Difference in Processor Active Heat Sink Based on Thermopile

The monitoring of processor temperature is crucial to increase its efficiency. One of the novel approaches is use the information not only about the CPU (Central Processing Unit) thermal state, but also about changing environmental conditions. The additional temperature difference sensor to monitor thermal changes in the processor environment is necessary. The sensor dedicated for active heat sink, often used inside laptops, was designed, fabricated and investigated. To fulfill the requirements and to match to the specific shape of the active heat sink, the hybrid sensor was proposed. It was composed of six thermocouples and fabricated using thick-film and LTCC (Low Temperature Cofired Ceramic) technology combined with wire thermocouples. Thick-film/LTCC flat substrates with thermoelectric paths ensured good thermal contact between the sensor and the monitored surface. The thermoelectric wires allowed adjusting the sensor to the complicated shape of the active heatsink. Three different versions of the sensor were realized and compared. All of them seem to be suitable for measuring the temperature difference in the given application and they can be used in further works.

A 33.6 $$\upmu$$m$$^2$$ 12.3 nW self-biased differential temperature sensor for thermal field monitoring

A 33.6 $$\upmu$$m$$^2$$ 12.3 nW self-biased differential temperature sensor for thermal field monitoring

On-Chip Thermal Profiling to Detect Malicious Activity: System-Level Concepts and Design of Key Building Blocks

This article introduces an on-chip anomaly monitoring system design approach that is based on thermal profiling and side-channel analysis. The strategy aims at the realization of nonintrusive hardware Trojan (HT) detection over the lifetime of the circuit under test (CUT). To evaluate the capability of the proposed HT detection system, the on-chip electrothermal coupling is modeled as part of the simulation technique, which associates local thermal activities with circuit-level power consumption using a standard electrical simulator. To monitor the thermal profiles on chips with high sensitivity to local temperature changes and the resilience to flicker noise, the sensor architecture described in this article is the first differential temperature sensor equipped with a chopping mechanism. A methodology is described to utilize principal component analysis (PCA) to extract critical information from the quantized output of the system for effective HT detection in the presence of noise. The complete sensor signal path of the system was designed and simulated with foundry-supplied device models (130-nm CMOS technology), and the impact due to process variations have been considered via Monte Carlo simulations. The results indicate that small Trojans with approximately 2 μW of power can be detected within the thermal profile of a CUT consuming more than 500 μW. As the first step to prove the feasibility of on-chip quantization in the HT detection system, a prototype 8-bit successive approximation register (SAR) analog-to-digital converter (ADC) was fabricated with 130-nm CMOS technology.

Design of A New Differential Scanning Calorimeter

The core component of DSC is a temperature difference sensor used to measure the temperature change of sample and reference material during reaction. Taking temperature difference sensor as the research object, a new DSC is designed, which uses many pairs of thermocouples in series to form a radiating thermocouple stack to improve the calorimetric sensitivity of the temperature difference sensor and reduce the measurement error caused by the uneven temperature distribution on the sensor. Through theoretical analysis, it can be seen that the original signal acquisition volume of the temperature difference sensor with multiple pairs of thermocouples has increased greatly, the calorimetric sensitivity is higher, and the error is smaller. Based on the finite element analysis software ANSYS, the steady state thermal analysis is performed on the high-sensitivity temperature difference sensor and the dumbbell-type temperature difference sensor respectively. The results show that the temperature difference of the high-sensitivity temperature difference sensor is 40.8% ∼ 52.3% lower than that of the dumbbell-type temperature difference sensor under different working temperatures, which greatly reduces the measurement error caused by the uneven temperature distribution.

Differential Temperature Sensors: Review of Applications in the Test and Characterization of Circuits, Usage and Design Methodology.

Differential temperature sensors can be placed in integrated circuits to extract a signature of the power dissipated by the adjacent circuit blocks built in the same silicon die. This review paper first discusses the singularity that differential temperature sensors provide with respect to other sensor topologies, with circuit monitoring being their main application. The paper focuses on the monitoring of radio-frequency analog circuits. The strategies to extract the power signature of the monitored circuit are reviewed, and a list of application examples in the domain of test and characterization is provided. As a practical example, we elaborate the design methodology to conceive, step by step, a differential temperature sensor to monitor the aging degradation in a class-A linear power amplifier working in the 2.4 GHz Industrial Scientific Medical—ISM—band. It is discussed how, for this particular application, a sensor with a temperature resolution of 0.02 K and a high dynamic range is required. A circuit solution for this objective is proposed, as well as recommendations for the dimensions and location of the devices that form the temperature sensor. The paper concludes with a description of a simple procedure to monitor time variability.

Прецизионные узкодиапазонные дифференциальные температурные датчики

Прецизионные узкодиапазонные дифференциальные температурные датчики

Optical differential temperature measurement with beat frequency phase fluorometry.

We present, to the best of our knowledge, a new method for differential temperature measurement based on thermal sensitivity of the fluorescence lifetime of thermographic phosphors. Pairs of thermographic phosphors are excited with intensity-modulated light at frequencies ω and ω+Δω. The phase shift Δθ of the summary fluorescence intensity beat signal envelope is measured. A prototype of a fluorometric differential temperature sensor is developed, and feasibility of the method is experimentally demonstrated with a Sm2+:SrFCl crystal and the D15->F70 transition for high thermal sensitivity. The observed linear dependence between envelope phase shift Δθ and temperature difference ΔT agrees with the theoretical prediction. Sensitivity of S=-0.97°/°C was achieved. This method could also be applied to differential measurements of any parameter affecting fluorescence lifetime.

Selectable Titanium-Oxide-Based Critical and Differential Temperature Sensor in a Single Devices

We propose a titanium oxide (TiOx)-based temperature sensor that can be operated in two ways, namely, by showing either abrupt or gradual metal–insulator transition (MIT) characteristics. For an as-prepared reliable TiOx-based MIT device, both abrupt and gradual MIT characteristics were observed under varying bias and temperature conditions. These results strongly demonstrate that two different types of temperature sensor (critical temperature sensor and differential temperature sensor) can be selectively operated by varying the applied bias in a single MIT device.

Differential temperature sensor with high sensitivity, wide dynamic range and digital offset calibration

The goal of this paper is twofold: first to add together all different causes that can alter the offset of a differential temperature sensor and, second, to present a new differential temperature sensor architecture that can digitally compensate for this behavior and therefore extends the sensor dynamic range. Measurements performed on a 65nm CMOS differential temperature sensor are presented to illustrate the discussion. As evolution of the state of the art, an automatic calibration procedure and the new sensor topology is presented. With this new topology, not only the thermal offset can be digitally calibrated, but the application field of differential temperature sensors is widened, being now suitable for use in measurements where both wide input range and high differential sensitivity are required.

Design and implementation of a 2 μA temperature-compensated MEMS-based real-time clock with ±4 ppm timekeeping accuracy

This paper presents the design and measurements of a temperature-compensated real-time clock based on a silicon resonator. The system exhibits timekeeping accuracy of ±4ppm over the −40 to 85°C temperature range. The current implementation is based on a TIA-based oscillator with a 27kHz MEMS resonator, a differential PTAT temperature sensor and a 2nd order ΣΔ ADC. The temperature compensation is performed by an on-chip DSP block. The system consumes 2μA of current and operates at 1.8V nominal supply. The resonator operates off a 1.2V DC bias without the need for a charge-pump or providing an external higher DC voltage. The integrated electronics interface has been implemented using a standard 0.18μm CMOS process.

All-Printed Differential Temperature Sensor for the Compensation of Bending Effects.

Because printed resistance temperature detectors (RTDs) are affected by tension and compression of metallic patterns on flexible or curved surfaces, a significant temperature-sensing error occurs in general. Hence, we propose a differential temperature sensor (DTS) to compensate the bending effect of the printed RTDs, which is composed of two serially connected similar meander patterns fabricated back-to-back on a polyimide polyethylene terephthalate substrate through a Dimatix DMP-3000 inkjet printer using silver nanoparticles. Under mechanical deformation, the resistance of the proposed DTS is not varied significantly under the same temperature environment because its patterns vary differentially as one side experiences tension while the opposite side experiences compression. A single meander pattern of the proposed DTS has a total length of 75 mm and device dimensions of 7 × 7 mm2. The total resistance variation is observed to be 15.5 Ω against the temperature variation from 0 to 100 °C, and the temperature coefficient of resistance is 1.076 × 10-3 °C-1. The proposed DTS exhibits no significant resistance change on bendability testing down to 2 mm diameter because of mechanical deformation. In addition, it is also used to detect the curvature of a body shape down to 2 mm diameter because its resistance changes by ±8.22% using a single meander pattern of DTS. The proposed sensor can be applied on a curved or flexible surface to measure relatively accurate temperature when compared to a single meander pattern.

Design of a Calibrated Temperature Difference Sensor Transducer for Monitoring Environmental Temperature Difference Applications

In this paper, a calibrated temperature difference sensor transducer is newly proposed for monitoring environmental temperature difference applications. The output signal is a pulse stream, and thus it could be easily sent over a wide range of transmission media, such as package switch network, radio, optical, infrared, ultrasonic, and so on. Another innovation is that the proposed calibration method can reduce the nonlinear error arising from the temperature difference sensors. By collocating with a temperature difference sensor, which has a range of temperature difference of 7.43 to 33.77 K, the corresponding output frequency ranges from 37.51 to 71.43 kHz. After calibration, the measured maximum frequency error is 1.35%. All functions of the proposed calibrated temperature difference sensor transducer were verified experimentally, and thus confirming its applicability to monitoring temperature difference of wall burn by a fire. The proposed calibrated temperature difference sensor transducer is suitable for use in monitoring temperature difference devices.

Flexible Electronics: Theoretical and Experimental Studies of Epidermal Heat Flux Sensors for Measurements of Core Body Temperature (Adv. Healthcare Mater. 1/2016).

On page 119, J. A. Rogers and co-workers present theoretical approaches, modeling algorithms, materials, and device designs for the noninvasive measurement of core body temperature by using multiple differential temperature sensors that attach softly and intimately onto the surface of the skin. The image shows the construction of differential temperature sensors using thermally insulating foam as the separation material.

Analysis of the flow imbalance in the KSTAR PF cryo-circuit

The KSTAR PF cryo-circuit is a quasi-closed circulation system in which more than 370g/s of supercritical helium (SHe) is circulated using a SHe circulator. The heated helium from superconducting magnet is cooled through sub cooler (4.3K). The circulator is operated at 4.5K and 6.5bar, and the pressure drop of the circuit is kept at 2bar in order to maintain the supercritical state and circulator stability. The circuit is connected with helium refrigerator system, distribution system, and supercritical magnet system. It has a hundred branches to supply supercritical helium to the poloidal field superconducting magnet. The branch was designed to optimize the operation conditions and they are grouped for one cryogenic valve has the same length within the cardinal principle of the optimization. Five cryogenic valves are installed to control the mass flow rate, and seven orifice mass flow meters, differential pressure gauges and temperature sensors were installed in front of the magnet in the distribution because upper magnet and lower magnet is symmetric theoretically. The cryogenic pipe line was manufactured with elevation about 10m between upper magnet and lower magnet. The inlet and outlet helium feed-through were installed at the coil inside in case of KSTAR PF1–PF5 upper magnet and lower magnet. The flow imbalance is caused by void fraction and it could be changed due to manufacturing process even if it has the same length of cooling channel. This creates an imbalance among cooling channels and temperatures are slightly different. The flow was reduced and detoured due to the pressure rise rapidly at inlet and outlet during magnet operation. Therefore, the orifice mass flow meters are installed in front of the PF1–PF5 upper magnet and lower magnet in order to investigate flow trend and the thermos-hydraulic behavior is analyzed during PF magnet operation.