Temperature Compensation Technique Research Articles

Passive Resistor Temperature Compensation for a High-Temperature Piezoresistive Pressure Sensor.

The main limitation of high-temperature piezoresistive pressure sensors is the variation of output voltage with operating temperature, which seriously reduces their measurement accuracy. This paper presents a passive resistor temperature compensation technique whose parameters are calculated using differential equations. Unlike traditional experiential arithmetic, the differential equations are independent of the parameter deviation among the piezoresistors of the microelectromechanical pressure sensor and the residual stress caused by the fabrication process or a mismatch in the thermal expansion coefficients. The differential equations are solved using calibration data from uncompensated high-temperature piezoresistive pressure sensors. Tests conducted on the calibrated equipment at various temperatures and pressures show that the passive resistor temperature compensation produces a remarkable effect. Additionally, a high-temperature signal-conditioning circuit is used to improve the output sensitivity of the sensor, which can be reduced by the temperature compensation. Compared to traditional experiential arithmetic, the proposed passive resistor temperature compensation technique exhibits less temperature drift and is expected to be highly applicable for pressure measurements in harsh environments with large temperature variations.

GA based management of strain response in RII-type single mode optical fiber

In this article, the strain behaviour of the depressed inner core triple clad single mode optical fiber is investigated. Both tensile and compressive types of axial strain are considered in simulations. The modal analysis of the fiber structure is based on linear polarization (LP) approximation method. Mode field diameter (MFD) of the fiber is selected as the indirect parameter for strain sensing task and investigating the MFD behaviour of the fiber, the strain sensitivity is augmented through independent adjustment of the structural parameters. Subsequently, a design procedure based on evolutionary genetic algorithm (GA) is introduced for consideration of simultaneous effect of all hyper-parameters of the fiber which yields the strain sensitivity of 15.96pmμε−1. The substantial sensitivity attained is as the inherence of complicated configuration in multilayer fiber as well as the GA based method. Furthermore, negligible temperature sensitivity of −6.97×10−7pmC−1 removes the temperature compensation technique which is inevitable stage of fiber optic measurement systems. Additionally, the simulation results admit the stable strain response of the proposed structure.

Temperature compensation technique for ring oscillators with tail current

A temperature compensation technique for ring oscillators with tail current is proposed and analysed. Both proportional to absolute temperature (PTAT) current source and constant current source are implemented to serve as the tail current. The constant current provides most of current for oscillation, and the PTAT current is for compensating the oscillator's temperature variation. The ring oscillator achieves high frequency-temperature stability.

A Temperature Compensation Technique for Near-Infrared Methane Gas Threshold Detection

Methane is the primary constituent of natural gas and is used in many industrial processes. Detection of the presence of methane is important, especially before it reaches explosive concentrations. Earlier sensor types are based on catalytic adsorption (which may limit the sensor lifetime) at elevated temperatures (requiring additional power and possibly compromising safety). Recently, optical sensors based on infrared (IR) absorption by hydrocarbon molecules have become an important research focus. One unsolved problem when using solid-state IR sources is that of optical flux variation due to heating. This paper introduces a novel power compensation approach for IR LEDs employed in gas detection, which accounts for variations in the optical flux of the source. The contribution of this paper is threefold. First, we propose the idea of compensating for emitted IR flux by means of pulsed junction voltage measurement and explain why this is effective. Second, we introduce a compensation algorithm which shows how to take advantage of this concept. Third, experimental results demonstrate that the discrimination algorithm is at least six times better than the uncompensated measurements. The convergence of the algorithm results in a stabilized measurement in less than 1 s.

Characterization and Vertical Elements Distribution of ZnGeP<sub>2</sub> Single Crystals

A large, crack-free ZnGeP2 single crystal with size of Φ26 mm×70 mm was grown in a vertical three-zone tubular furnace by modified vertical Bridgman method, i.e. real-time temperature compensation technique with small temperature gradient in double-wall quartz ampoule. The as-grown single crystal was characterized by X-ray diffractometer (XRD), energy dispersive spectrometer (EDS), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). It was found that there is a face of (100) and its second-order XRD peaks were observed. The vertical elements distribution of the main part of the grown crystal has a stoichiometric ratio which is close to the ideal stoichiometry of 1:1:2. The IR transmittance of a sample of 2.5 mm thickness is above 58% in the range from 3500 to 800 cm-1. All these results demonstrate that the quality of the ZnGeP2 single crystal grown by the modified method is good, and could be used in the preparation of devices.

A Temperature Compensation Concept for a Micromachined Film Bulk Acoustic Resonator Oscillator

We present a temperature compensation technique of a film bulk acoustic resonator (FBAR)-based oscillator by tuning the supply voltage of the oscillator. The FBAR-based oscillator uses a high- $Q$ FBAR that is made of a thin ZnO piezoelectric film sandwiched by two electrodes. The FBAR is significantly sensitive to temperature change, consequently resulting in large temperature sensitivity of the FBAR-based oscillator. In this paper, we present a temperature compensation technique that improves the temperature coefficient (TCf $_{\mathrm {osc}}$ ) of a 1.625-GHz FBAR-based oscillator from −118 ppm/K to less than 1 ppm/K by tuning the supply voltage of the oscillator. The tuning technique has a large frequency tunability of −4305 ppm/V.

A Sub-<inline-formula> <tex-math notation="LaTeX">${\boldsymbol kT}/\boldsymbol q$ </tex-math></inline-formula> Voltage Reference Operating at 150 mV

We propose a subthreshold CMOS voltage reference operating with a minimum supply voltage of only 150 mV, which is three times lower than the minimum value presently reported in the literature. The generated reference voltage is only 17.69 mV. This result has been achieved by introducing a temperature compensation technique that does not require the drain–source voltage of each MOSFET to be larger than $4 kT/q$ . The implemented solution consists in two transistors voltage reference with two MOSFETs of the same threshold-type and exploits the dependence of the threshold voltage on transistor size. Measurements performed over a large sample population of 60 chips from two separate batches show a standard deviation of only 0.29 mV. The mean variation of the reference voltage for $V_{\rm DD}$ ranging from 0.15 to 1.8 V is 359.5 $\mu $ V/V, whereas the mean variation of V $_{\rm {REF}}$ in the temperature range from 0 °C to 120 °C is 26.74 $\mu $ V/°C. The mean power consumption at 25 °C for $V_{\rm DD}= 0.15$ V is 26.1 pW. The occupied area is $1200~\mu $ m $^{2}$ .

Experimental Study and Analysis of Hydrostatic Pressure Sensitivity of Polymer Fibre Bragg Gratings

The intrinsic hydrostatic pressure sensitivity of polymer optical fiber Bragg grating (POFBG) with different diameters are investigated. POFBGs are inscribed in single-mode polymer fiber and etched down to different diameters. We have experimentally demonstrated that the material properties of the polymer optical fiber can change after etching and thus the etching procedure can have an impact on the pressure sensitivity of the POFBG. It is observed from the experimental results that hydrostatic pressure induces a positive wavelength shift to the POFBG and the pressure sensitivity of the POFBG shows significant increase as the fiber diameter reduces through etching. A pressure sensitivity of 0.20 pm/kPa is obtained for an unetched POFBG while for an etched POFBG with 55- $\mu$ m diameter a sensitivity of 0.75 pm/kPa is observed. Temperature compensation techniques are also successfully implemented to extract the true intrinsic pressure sensitivity of the POFBG. Through this study, the intrinsic pressure sensitivity of POFBG with different diameters are obtained and also the significance of etching and its impact on pressure sensitivity is demonstrated. This information can lead to further research and development on high sensitivity pressure transducers based on etched POFBGs.

Advanced Temperature Compensation and Correction Techniques in Thermal Anemometry

Thermal anemometry measurements of non isothermal flows require the use of a temperature compensation or correction method. In this article, the principles of operation of methods for reduction of temperature influence on the flow velocity measurement are discussed. The study also compares the methods and discusses the conditions for their application. The advanced temperature compensation and correction methods are presented in uniform notation and concerns hot-wire anemometers operating in the most commonly used standard constant-temperature mode.

Process, voltage and temperature compensation in a 1-MHz 130nm CMOS monolithic clock oscillator with 2.3% accuracy

This paper presents an on-chip process, voltage and temperature (PVT) compensation technique for a 1-MHz monolithic clock oscillator in a CMOS process. The oscillator is based on carrier mobility and frequency-to-voltage converter (FVC), which is based on charge pump circuit. An adaptive charge current maintains a constant frequency without trimming. Furthermore, a reference voltage with a second-order temperature coefficient further compensates the variation of frequency with temperature. It improves the accuracy of existing carrier-mobility-based oscillator, from 4.5% to 2.3%. The circuit was designed in a 130 nm CMOS 3.3 V device process. The results show that the output frequency is within 2.3% variation in the worst case. The variations of frequency with process, temperature (−40 to 125°C) and power supply are within 1.8%, 0.8% and 0.2%/V, respectively. It achieves a CMOS monolithic clock oscillator insensitive to PVT.

A novel temperature compensated piezoresistive pressure sensor

The main drawback of current piezoresistive pressure sensors is the drop of output voltage with increase in the operating temperature which severely reduces the measurement accuracy. This paper presents a novel passive technique for temperature compensation of silicon piezoresistive pressure sensors. The built-in compensation technique eliminates the need for expensive and time consuming calibration process required for each sensor inside a fabricated batch. In this technique, extra polysilicon resistors with negative Temperature Coefficient of Resistivity (TCR) are employed for compensation purpose. Through applying this technique, Temperature Coefficient of Sensitivity (TCS) of the conventional non-compensated sensor was reduced to zero. Analytically derived equations and verified Finite Element Model considering mechanical, piezoresistive and electrical characteristics of the sensor are adapted to analyze the behavior of the sensor. The implementation of the introduced technique is compatible with conventional MEMS devices fabrication process. The compensated sensor is advantageous for pressure measurement in harsh environments with temperature variations.

Lock-in amplifiers for AMR sensors

Anisotropic magnetoresistive (AMR) magnetic sensors are often chosen as the magnetic transducer for magnetic field sensing in applications with low to moderate magnetic field resolution because of the relative low mass of the sensor and their ease of use. They measure magnetic fields in the order of the Earth magnetic field (with typical sensitivities of 1‰/G or 10−2‰/μT), have typical minimum detectable fields in order of nT and even 0.1nT but they are seriously limited by the thermal drifts due to the variation of the resistivity with temperature (∼2.5‰/°C) and the variation of the magnetoresistive effect with temperature (which affects both the sensitivity of the sensors: ∼2.7‰/°C, and the offset: ±0.5‰/°C). Therefore, for lower magnetic fields, fluxgate vector sensors are generally preferred.In the present work these limitations of AMR sensors are outlined and studied. Three methods based on lock-in amplifiers are proposed as low noise techniques. Their performance has been simulated, experimentally tested and comparatively discussed. The developed model has been also used to derive a technique for temperature compensation of AMR response. The final goal to implement these techniques in a space qualified applied specific integrated circuit (ASIC) for Mars in situ exploration with compact miniaturized magnetometers.

Design of Strain-Sensing Devices in Microscale by Using Surface Plasmon Polaritons

We have presented a strain-sensing device in microscale by using surface plasmon polaritons and multimode interference effects. The device is numerically investigated by the finite-difference time-domain method. Optimum depths and length of the structure are designed for sensing a strain. The size of the designed structure is several micrometers and is about a thousandth compared with a fiber Bragg grating strain sensor. The sensitivity of the designed structure is 11.34 pm/μ𝜖 that is about ten times larger than that of a fiber Bragg grating strain sensor. The temperature sensitivity of the designed structure is 34.43 pm/ ∘C. This temperature sensitivity is three times larger than that of a fiber Bragg grating strain sensor. Therefore, temperature compensation techniques are needed for the structure. The presented structure has a simple design such as a plasmonic waveguide with a trench structure. The simple structural design device has a capability of being used in micro- and nano-electromechanical systems.

An adaptive filter–based temperature compensation technique for structural health monitoring

Temperature variations have significant effects on guide wave propagation and therefore increase the detection uncertainty of the guided wave–based structural health monitoring system. A novel temperature compensation technique combining an adaptive filter and optimal baseline selection is developed to enhance the robustness and effectiveness of guided wave–based damage detection. The adaptive filter is the finite length unit impulse response digital filter based on adaptive linear neuron network. This article focuses on three main issues for practically implementing the proposed method: (a) establishment of temperature compensation standard, (b) parameter design of compensation filter, and (c) determination of temperature gradient to reduce the number of selected baselines. Experiments are conducted on two stiffened composite plates to verify the proposed method for effective and robust temperature compensation under a large temperature range from −40°C to 80°C. Results show that temperature interval for baselines of low-frequency signals, such as 50 kHz, can be up to 20°C to provide good temperature compensation with the proposed method, while temperature interval for baselines of high-frequency signals, such as 450 kHz, can be up to 12°C.

Research on the temperature influence and compensation technique in a magneto-elastic cable tension sensor

The magneto-elastic cable tension sensor has numerous advantages. For example, it is the ideal method for measuring the cable tension in a large span cable-bridge; however, the sensor is also temperature-sensitive, and as such, the temperature influence on the sensor is a significant factor. In this paper, the principle of cable tension sensor based on magnetic-elastic effect is introduced. And, the theory of temperature influence magneto-elastic material is thoroughly analysed. On the basis of Jiles-Atherton model, which introduced the Curie temperature as an additional parameter, a magnetic-thermo coupling model for the magnet elastic cable tension sensor is constructed. By analysing temperature and the physical parameters of the model, a novel method of compensating for the temperature by adjusting the bias magnetic field is proposed. Theoretical analysis experimental work indicate that the model is a practical means of compensating for temperature influence.

Temperature Compensation Technique in Cable Tension Sensor Based on Magneto-Elastic Effect

Magneto-elastic cable tension sensor have a number of advantages, it will be ideal method to measure cable tension in large span cable-bridge, but the sensor is sensitive to temperature, so the temperature influence is not negligible to sensor. In this paper, the principle of cable tension sensor based on magnetic-elastic effect is introduced, the common temperature compensation technique are detail analyzed. A novel method of temperature compensation by adjusting the bias magnetic field is put forward, by theoretical analysis and experiment, indicated that it is feasible to compensated the temperature influence.

Process, Voltage and Temperature Compensation Technique for Cascode Modulated PAs

This paper presents a process, voltage and temperature (PVT) compensation method for a cascode modulated polar power amplifier (PA). It is shown that it is possible to create a baseband replica circuit of the PA that has the same AM-AM nonlinearity as the PA itself. The replica circuit, that represents a transistor level model (empirical model) of the cascode modulated PA, is utilized in a PA analog predistorter. The analog predistorter linearizes and compensates for PVT variation of the cascode modulated PA. The empirical model is placed in the negative feedback of an operational transconductance amplifier. The predistorted varying envelope signal is applied to the cascode gate of the PA. It is shown that the proposed PVT compensation technique significantly reduces the PVT spread of the PA linearity indicators and improves the PA linearity. Simulations were performed in a 0.13 μm CMOS process.

Temperature-Stable Silicon Oxide (SilOx) Micromechanical Resonators

This paper presents a passive temperature compensation technique that can provide full cancellation of the linear temperature coefficient of frequency (TCF1) in silicon resonators. A uniformly distributed matrix of silicon dioxide pillars is embedded inside the silicon substrate to form a homogenous composite silicon oxide platform (SilOx) with nearly perfect temperature-compensated stiffness moduli. This composite platform enables the implementation of temperature-stable microresonators operating in any desired in- and out-of-plane resonance modes. Full compensation of TCF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> is achieved for extensional and shear modes of SilOx resonators resulting in a quadratic temperature characteristic with an overall frequency drift as low as 83 ppm over the industrial temperature range ( -40°C to 80°C). Besides a 40 times reduction in temperature-induced frequency drift in this range, SilOx resonators exhibit improved temperature stability of Q compared with their single crystal silicon counterparts.

A 0.007-${\rm mm}^{2}$ 108-${\rm ppm}/^{\circ } {\rm C}$ 1-MHz Relaxation Oscillator for High-Temperature Applications up to 180 $^{\circ } {\rm C}$ in 0.13-$\mu {\rm m}$ CMOS

Reliable high-temperature CMOS oscillators are required for clock or time-base generation in several applications including data acquisition for aerospace, automotive control, oil field instrumentation, and pulp and paper digesters. In this paper, we present low-complexity resistive and capacitive temperature-compensation techniques for CMOS relaxation oscillators. In such oscillators, the frequency of oscillation is a function of a resistor-capacitor product. The resistive compensation technique employs a recently proposed monolithic resistor with a given temperature coefficient (TC) that uses contacts to adjust the TC of the resistor. The capacitive compensation technique is based on using a varactor to adjust the value of the timing capacitance over temperature to compensate for the high-temperature junction leakage current and to keep the oscillation frequency relatively constant. A prototype oscillator based on the proposed techniques is implemented in a standard 0.13-μm CMOS process and reliably operates over 25 to 180 °C. Measured results show that over the temperature range of interest the compensated oscillator achieves a temperature coefficient of 108 ppm/°C. The oscillator along with its output drivers occupies 7200 μm2 (2.3 × to 114 × smaller than state-of-the-art designs) and consumes 428 μW from a 2.5 V supply. For supply variations between 2 and 3 V, the frequency variation is ±1.09%/V.

Development of mutual inductance type sodium level detectors for PFBR

The 500MWe Prototype Fast Breeder Reactor (PFBR) is under advanced stage of construction at Kalpakkam, India. Continuous and discontinuous level sensors working on mutual inductance principle is used in PFBR for monitoring sodium level as well as for safety. The wide and high operating temperature, highly chemically active nature of sodium and its reaction with air make the sodium instrumentation special over conventional instrumentation. The traditional sodium level sensors such as Resistance Type Level Probe (RTLP) for discrete level measurements and MI type continuous level probe for continuous level measurement is used in Fast Breeder Test Reactor (FBTR). The challenges involved in making traditional continuous level sensors suitable for PFBR, include development of mechanically robust level sensors of longer length with better resistance to vibration, new method of temperature compensation to improve the accuracy over wide operating range from 150 to 550°C and improved electronics circuit with better features. MI type discrete level probe has been developed as improvement over RTLP. This paper highlights construction of longer level probes with leak tight arrangement, performance evaluation of prototype level probes, recent development on temperature compensation technique, improvement in electronics and development of noncontact type discrete level probe for PFBR.