Rapid Temperature Measurement Research Articles

Fast-Response Fiber-Optic FPI Temperature Sensing System Based on Modulated Grating Y-Branch Tunable Laser

In this paper, a cost-effective and miniaturized instrument is proposed, which is based on a tunable modulated grating Y-branch (MG-Y) laser for rapid temperature measurement using a Fabry-Perot interferometer (FPI) sensor. The FPI sensor with a 1 463-µm cavity length is a short segment of a capillary tube sandwiched by two sections of single-mode fibers (SMFs). This system has a broad tunable range (1 527 nm–1 567 nm) with a wavelength interval of 8 pm and a tuning rate of 100 Hz. Temperature sensing experiments are carried out to investigate the performance of the system by demodulating the absolute cavity length of the FPI sensor using a cross-correlation algorithm. Experimental results show that the sensor can reach the response time as short as 94 ms with the sensitivity of 802 pm/°C. Benefiting from the homemade and integrated essential electrical circuits, the entire system has the small size, low cost, and practical application potential to be used in the harsh environment for rapid temperature measurement.

Rapid Temperature Measurement of Meteorological Detection System Based on MEMS

This paper is based on a meteorological detection system, which contains MEMS barometric pressure sensors, MEMS temperature sensors, MEMS humidity sensors and GPS receiver. The micro control unit of this system is based on C8051F120 microcontroller. By Comparing SHTXX series of temperature and humidity sensor and PT100 thermal resistance, we obtain a measurement scheme that can measure environment temperature rapidly and relatively accurate when the volume, weight and power are limited. It can meet the harsh environments and high reliable needs. In addition, the simulation analysis and the experiment of temperature are carried out.

The Application and Dynamic Temperature Test Methods of Micro Thin Film Resistor Sensor

Based on the rapid response advantages and test problems of the thin film resistor, the analysis and research on two aspects are focused: First, the thin film resistor is used as a current sensor which is applied in high-voltage DC transformer. The structure and performance of the thin film resistor are analyzed and simulated. Second, the dynamic characteristics of the thin film resistor are tested by indirect temperature measurement method. The problem of current rapid temperature measurement is solved. The dynamic temperature characteristic curve of the thin film resistor is analyzed by using multi-exponential spectral analysis method. The thermal characteristics of the fine structure for the thin film resistor are described by spectral characteristics. Moreover, more test information of the fine structure from comprehensive test results is separated to guide the improvement of the thin film resistor structure.

FEM simulation and experimental verification of temperature field and phase transformation in deep cryogenic treatment

Combining with the low temperature material properties and the boiling heat transfer coefficient of specimen immersed in the liquid nitrogen, a numerical model based on metallo-thermo-mechanical couple theory was established to reproduce the deep cryogenic treatment (DCT) process of a newly developed cold work die steel Cr8Mo2SiV (SDC99). Moreover, an experimental setup for rapid temperature measurement was designed to validate the simulation results. The investigation suggests that the differences in temperature and cooling rate between the surface and core of specimen are very significant. However, it should be emphasized that the acute temperature and cooling rate changes during DCT are mainly concentrated on the specimen surface region about 1/3 of the sample thickness. Subjected to DCT, the retained austenite of quenched specimen continues to transform to martensite and finally its phase volume fraction reduces to 2.3%. The predicted results are coincident well with the experimental data, which demonstrates that the numerical model employed in this study can accurately capture the variation characteristics of temperature and microstructure fields during DCT and provide a theoretical guidance for making the reasonable DCT procedure.

An alternative method to develop fibre grating temperature sensors using the fibre loop ringdown scheme

We present a new method to develop fibre Bragg grating (FBG)-based temperature sensors using the fibre grating loop ringdown (FGLRD) technique. With this novel approach, temperature is sensed by measuring the wavelength-dependent optical loss resulting from the temperature variations incurred in the FBG. The sensor incorporates a standard telecommunications diode laser and an inexpensive photodetector and achieves rapid temperature measurements in a time domain (measuring the ringdown time). Apparent advantages of this method over the current FBG-OSA approach include the high measurement resolution and low instrument costs. A temperature sensor (type I) using a standard off-the-shelf single-mode bare FBG as the sensing element has been developed and it achieved an absolute measurement resolution of 0.18 °C (based on 3-σ) limited by the precision of the temperature calibration source used in the experiment. To the best of our knowledge, this is the highest measurement resolution of an FBG-based temperature sensor using a standard bare FBG. Additionally, the general applicability of the method has also been evaluated by constructing a temperature sensor (type II) using a long period grating. Discussions on the advantages and limitations of the FGLRD method as compared with the current FBG-OSA scheme are presented.

Wavelength modulation absorption spectroscopy with 2 f detection using multiplexed diode lasers for rapid temperature measurements in gaseous flows

Multiplexed fiber-coupled diode lasers are used to probe second-harmonic line shapes of two near-infrared water absorption features, at 1343 nm and 1392 nm, in order to infer temperatures in gases containing water vapor, such as combustion flows. Wavelength modulation is performed at 170 kHz, and is superimposed on 1-kHz wavelength scans in order to recover full second-harmonic line shapes. Digital waveform generation and lock-in detection are performed using a data-acquisition card installed in a PC. An optimal selection of the modulation indices is shown to greatly simplify data interpretation over extended temperature ranges and to minimize the need for calibration when performing 2 f ratio thermometry. A theoretical discussion of this optimized strategy for 2 f ratio thermometry, as well as results from experimental validations in a heated cell, at pressures up to atmospheric, are presented in order to illustrate the utility of this technique for rapid temperature measurements in gaseous flow fields.

High precision, fast ultrasonic thermometer based on measurement of the speed of sound in air

This study presents a microcomputer-based ultrasonic system which measures air temperature by detecting variations in the speed of sound in the air. Changes in the speed of sound are detected by phase shift variations of a 40 kHz continuous ultrasonic wave. In a test embodiment, two 40 kHz ultrasonic transducers are set face to face at a constant distance. Phase angle differences between transmitted and received signals are determined by a FPGA digital phase detector and then analyzed in an 89C51 single-chip microcomputer. Temperature is calculated and then sent to a LCD display and, optionally, to a PC. Accuracy of measurement is within 0.05 °C at an inter-transducer distance of 10 cm. Temperature variations are displayed within 10 ms. The main advantages of the proposed system are high resolution, rapid temperature measurement, noncontact measurement and easy implementation.

Multiplex H $_2$ CARS thermometry in a microwave assisted diamond CVD plasma

Rapid temperature measurements in a low pressure, microwave assisted, diamond CVD plasma are reported. By using a “modeless” laser as the Stokes source for H\(_2\) CARS, accurate single-shot and averaged temperatures were obtained which agreed with values obtained from laser induced fluorescence measurements. The speed of data acquisition afforded by multiplex CARS allowed variations of temperature to be monitored with changing plasma conditions induced by variations of pressure, gas composition and microwave power. The application of the technique for “on-line” monitoring of plasma processes is briefly discussed.

Issues in high-speed pyrometry

A brief summary is given of the developments in optical techniques for rapid temperature measurement during the last three decades in two national laboratories, the National Institute of Standards and Technology in the USA and the Istituto di Metrologia "G. Colonnetti" in Italy. Results of research conducted in originating and advancing the state-of-the-art in high-speed (millisecond- and microsecond-resolution) pyrometry for measurement of temperatures in the range 1000 K to 5000 K are discussed. The main emphasis is on several key issues related to high-speed pyrometry including: high-speed operation, calibration of pyrometers, determination of true temperature and high-temperature reference points. Anticipated future directions in research, developments and applications in high-speed pyrometry are briefly discussed.

Thermocouple sensor for rapid temperature measurements during ignition and early phase combustion of packed propellant beds

Flame-spreading processes during the ignition of ballistic events have long been studied by pressure measurements and visual records from high-speed film. While optical temperature measurements have been utilized, they are not useful much below 1500 K. A fine-wire platinum versus 10% Rh/platinum thermocouple probe was designed to measure gas temperature in a packed propellant bed over the range from the initial bed temperature (295 K) to more than 2000 K. Probe mounts were designed to provide sufficient physical support and protection for the thermocouples and yet minimally perturb the flow environment. Three diameters of fine-wire thermocouples were tested for survivability and time response in the simulated pressure-wave environment of ignition of a propellant bed. The largest diameter thermocouple (3 mil or 76 μm) exhibited a response time too great (3 ms). The smallest diameter (1 mil or 25 μm) exhibited the shortest response time (0.4 ms) and would be the thermocouple of choice for this experiment; however, it was not used in the current experiments due to difficulties in probe fabrication and consideration of wire strength. For this application, a 2 mil (51 μm) diameter thermocouple was chosen. The lag time for this thermocouple was estimated at approximately 1.5 ms. Corrections to the temperature for catalytic activity (<1 K) and radiative cooling (60 K in the plateau region) were estimated. Examples of temperature histories during ignition of M30A1 and M43 propellants are also included.

Comparison of Pulmonary Artery, Rectal, and Tympanic Membrane Temperatures in Adult Intensive Care Unit Patients

Tympanic thermometry using infrared thermography technology offers a noninvasive, rapid temperature measurement tool which may be useful for selected intensive care unit (ICU) patients. Multiple comparisons of pulmonary artery catheter (PAC), rectal (R), and tympanic membrane (TM) temperatures were performed in nine adult ICU patients using PAC temperatures as the gold standard. The correlation between R (r = 0.93) and PAC was significantly better than TM (r = 0.74) temperatures. However, PAC (37.2 +/- 0.06 degrees C; mean +/- SEM) and TM (37.1 +/- 0.08 degrees C) temperatures were not significantly different, whereas R (37.6 +/- 0.07 degrees C) was significantly warmer than both (P less than .05). Differences between either R (+0.4 degrees C) or TM (-0.1 degrees C) and PAC temperatures were consistent over selected ranges between 35 degrees C and 40 degrees C. The performance of TM and R was similar in the ability to predict PAC temperatures.

A myothermal analysis of the myosin crossbridge cycling rate during isometric tetanus in normal and hypothyroid rat hearts.

Hypertrophied rabbit heart papillary muscles (thyrotoxicosis), with a high V1/V3 myosin isoenzyme ratio and contractile protein ATPase activity, have a high velocity of unloaded shortening and a decrease in the myothermal economy of isometric twitch force development and dissipation; in hypertrophied hearts (pressure overload) with a low V1/V3 isoenzyme ratio and ATPase activity, the converse was found to be true (Am J Cardiol 1979; 44:947-953; Fed Proc 1982; 41:192-198). In the present study the confounding problem of internal shortening, which takes place during force development and dissipation in the isometric twitch, is minimized by carrying out measurements of the rate of heat liberation during the plateau phase of tetanic force maintenance. The studies are further extended to another species (rat) where the V1/V3 myosin isoenzyme ratio is altered by treating the animal with propyl thiouracil added to the drinking water (PTU); here the contractile protein alteration occurs with myocardial atrophy rather than hypertrophy. High resolution, rapid temperature measurements are made in tetanically stimulated isometrically contracting rat heart papillary muscles from normal (high V1/V3 ratio) and PTU treated (low V1/V3 ratio) rats to assess the relationship between contractile protein performance (crossbridge cycling rate) in the intact muscle and that under controlled conditions in isolated myofibrils. In papillary muscles from the normal heart the crossbridge cycling rate (+/- SEM) during force maintenance was 6.53 (+/- 1.73) cycles/second compared with 3.13 (+/- 0.24) and 0.53 (+/- 0.17) cycles s-1 in the myofibril at high and low ionic strength, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Temperature Distribution in White-Oak Laminated Timbers Heated in a High-Frequency Electric Field

Abstract High-frequency dielectric heating has been applied to the process of laminating commercial white-oak ship timbers. Specimens 6 × 6 × 24 in., composed of eight laminations ¾ × 6 × 24 in., were heated both with and without glue to study the temperatures obtaining in the glue-line areas. The uniformity of temperatures depends upon the density, moisture content, and arrangement of the laminations, direction of the electric field, and thermal insulation of the heated material. The effect of these variables is greater when the electric field and glue lines are parallel than when they are mutually perpendicular. Thermocouples were used for rapid temperature measurement. A method of heating the sides of timbers effectively was developed.