Resistance-temperature Characteristics Research Articles

Calibrating Cylindrical Hot-Film Anemometer Sensors

Abstract We report the results of 82 separate calibrations of cylindrical, platinum hot-film anemometer sensors in air. The calibrations for each sensor involved a determination of its temperature-resistance characteristics, a study of its heat transfer in forced convection, and an investigation of its yaw response. Because most sensors were calibrated more than once during a 28 month period, the resistance-temperature data allowed us to look at sensor aging. We found no conclusive evidence that either the reference resistance, R0, or the temperature coefficient of resistance, α, changed with time (months to years). Hence, frequent, full calibrations of the sensors are probably unnecessary. It is, nevertheless, wise to measure R0 whenever possible. The convective heat transfer relation that we derive predicts the Nusselt number of the sensor as a linear function of R0.40, where R is the Reynolds number based on sensor diameter (1 ≤ R ≤ 43). For the 53-μm- diameter sensors that we used, this heat transfer ...

Properties of industrial-grade platinum–cobalt resistance thermometers between 1 and 27 K

The stability at 20 K of five industrial-type platinum–cobalt resistance thermometers on thermal cycling has been studied together with their resistance-temperature characteristics between 1 and 27 K and their self-heating. The stability at 20 K on cycling between room temperature and 20 K is of the order of 10 mK and on cycling between 100 and 20 K is a few mK. Differences in the resistance-temperature relationships of the thermometers are very small, but the self-heating effects are relatively large, particularly below 4 K.

Use of ceramic-encapsulated rhodium-iron alloy resistance thermometers below 80K: thermometric properties and stability

The resistance-temperature characteristics and self-heating of three ceramic-encapsulated rhodium-iron alloy resistance thermometers have been studied below 80K. The stability of the thermometers at 20K on repeated thermal cycling between 20 and 288K proved to be excellent (+or-25 mu Omega over 20 cycles). Small changes in resistance (up to 0.6 m Omega ) were noted on physical handling of the thermometers.

High temperature resistivity characteristics of nonstoichiometric V2O3

The resistivity anomaly encountered in stoichiometric V2O3 is gradually suppressed with increasing density of cation vacancies. These observations are discussed in terms of related findings reported in the literature.

Electronic transition in CeAl 2 under pressure

The strong anomalies in the resistance-temperature characteristic of CeAl 2 disappear continously with increasing pressure between 30 and 130 kbar. From the similarity to the γ/α transition of Ce metal we suggest, that CeAl 2 undergoes an analogous electronic transition under pressure as pure Ce.

SUPERCONDUCTIVITY AND PERCOLATION IN Al-Ge FILMS

A double superconducting transition in co-evaporated Al-Ge films can be observed in both their resistance-temperature and current-voltage characteristics. An explanation is offered in terms of percolation theory.

Influence of technology on the metrological properties of gold–chromium alloy pressure gauges

This paper discusses the technological processing of the gold–chromium (with 1.95±0.05% Cr) alloy pressure gauge, optimized to get the best metrological properties. It also presents experimental results of thermal and pressure measurements of the alloy. It was found that the Au–Cr pressure gauge, properly seasoned in the controlled seasoning process, is completely free of hysteresis in resistance due to pressure changes, with uncertainty of less than 0.4 bar in 6000 bars range. Resistance-pressure and resistance-temperature characteristics didn’t change during the pressure or temperature cycling. It is also shown in the paper that there is a possibility of employing Au–Cr pressure gauges for measurements of high pressures up to about 20 000 bars.

An equation to fit the resistance-temperature characteristics of germanium-doped sensors at high temperature

In 1970, a review1 was published covering progress in low temperature primarily during the 1960's. The intent of this paper is to extend the review process through the intervening decade to the present, specifically from 1969 to 1981. The review concentrates on work done in the temperature region between 1 K and about 100 K. The section headings are as follows: Temperature Scales; fixed points and vapour pressure thermometry; gas thermometry; resistance and diode thermometry; thermoelectric, capacitance, and noise thermometry; other methods of thermometry; environmental effects; and instrumentation, methods, and materials. The paper's bibliography includes more than 400 references.

Thermometry using [formula omitted] W carbon resistors in a temperature region around 10 mK

The resistance-temperature characteristics of 1 8 W carbon resistors of grade ERC-18SG, manufactured by Matsushita, with the nominal values of 48, 82, 100, 220, and 330 Ω have been measured in the region 4.2 K-25 mK and their application as thermometers in this region is confirmed. For the 82 Ω resistor, measurements were taken at temperatures below 10 mK. The temperature dependence of the resistance was found to be linear on the log-log plot over a wide range below 50 mK. The sensitivity remains finite even at 6 mK, but below 10 mK rapid measurements were prevented by a considerable increase in the thermal relaxation time. Measurement of the characteristics of several 100 Ω resistors from two different sets showed that resistors from the same set separate into two groups with different characteristics. This becomes appreciable at temperatures below 4.2 K, so it is difficult to predict the behaviour of Matsushita resistors below 4.2 K from the characteristics at higher temperatures.

The electrical resistivity and resistance-temperature characteristics of thin titanium films

In this communication are described the results on the electrical resistivity and resistance-temperature characteristics of titanium films, measured in vacuum. They were evaporated onto soda glass microscope slides at room temperature in a sputter-ion pumped glass belljar vacuum system at about 5×10 -8 torr. The films varied in their thickness from 50 to 1100 Å, and the resistivity was very high for the thinnest films but for the thickest ones it approached approximately double the bulk value. The measured resistivities for the continuous freshly prepared films are too high to be explained on the basis of the Fuchs-Sondheimer theory 1, 2 for diffuse scattering, and are attributed to porosity and the gaseous impurities taken down during and after their formation. The temperature coefficient of resistance (TCR) was negative for films less than 50–60 Å thick but positive for thicker ones. A bulk mean free path of 285 Å in titanium was calculated at room temperature. A brief survey is made of the similar work available on titanium films in the literature, and our results are discussed and compared with it.

La-Doped BaTiO<sub>3</sub> Ceramics with Bi<sub>2</sub>O<sub>3</sub> as a Grain Boundary Element

It is known that sintered bodies of semiconducting barium titanates or its solid solutions have a large positive temperature coefficient of resistivity above and near the Curie temperature. They have a negative temperature coefficient of resistivity normal as usual semiconductors below the Curie temperature. At the Curie temperature the tetragonal to cubic transition takes place and the resistivity anomaly around the temperature has been related to the transition. At the transition temperature, orthorhombic to tetragonal, however, no anomaly in the resistivity-temperature characteristic has been found on the sintered bodies reported so far.The present authors modified the texture of sintered bodies of semiconducting barium titanate with bismuth oxide penetrated along grain boundaries. When non-ohmic contact electrodes were applied to the texture modified specimens another anomaly in the resistivity-temperature characteristic appeared above the orthorhombic to tetragonal transition temperature in addition to the anomaly above the Curie temperature. The nonlinear current-voltage and capacitance-voltage characteristics measured on present specimens with asymmetric electrodes (non-ohmic contact electrode to the one side and ohmic contact to the other side), showed the existence of a surface barrier-layer in the interface between the non-ohmic electrode and the body with texture modified. The nonlinear curve in the capacitance-voltage characteristic was not expressed by the relation 1/C2=2(Vd-V)/eεsNd (Vd is a built-in voltage at a barrier, εs is a dielectric constant in a barrier-layer and Nd is the density of ionized donor centers) above a certain reverse bias which was dependent on a measuring temperature. It seems reasonable to assume that the surface barrier-layer is made up of a inversion layer and a bismuth oxide layer. The barrier gave rise to the anomaly around a room temperature. Under a higher electric field the effect of the surface barrier becomes negligible small compared with the effects by barriers given across the grain boundaries in the sintered body which is considered to give rise to the anomaly above the Curie temperature. It may be considered that by the addition of bismuth oxide the concentration of trap centers changed; the concentration of trap centers affects the height and width of the barrier between semiconducting grains and of the barrier between the non-ohmic electrode and the pellet surface.

Evaporated Hall generators of mercury telluride

Analysis of the usefulness of mercury telluride thin-films for preparing Hall generators is made in the paper. Hall generators were obtained by evaporation of solid polycrystalline HgTe on a mica substrate. The temperature of the heater was about 280°C, that of the substrate −10°C. The evaporation process was carried out in a vacuum of 10 −5 torr. Films obtained in such a way were heat treated in the atmosphere of mercury vapours and argon to correct the non-stoichiometry of mercury, that arose due to the partial dissociation of the material. Films with thicknesses between 0·1 and 3 μ were prepared. Strong thickness dependence of the following basic properties of thin-films was found: Hall coefficient ( R H ), resistivity (ρ) and mobility of carriers (μ). For a thickness of 0·1 μ the following mean figures for the above parameters were measured: R H = 15 cm 3/ C, ρ = 7·5 × 10 −2 Ω- cm, μ e = 205 cm 2/ V-sec; for a thickness of 3 μ R H = 12·2 cm 3/ C, ρ = 2·9 × 10 −3 Ω- cm, μ e = 4100 cm 2/ V-sec . All films in temperatures higher than 200°K were of intrinsic conductivity. The main advantage of Hall generators made of mercury telluride is their good mechanical properties, mainly elasticity. Owing to the use of a thin mica substrate the Hall generators could be bent with radius of curvature of about 1 cm. The thickness of Hall generators is limited by the thickness of the substrate and therefore the Hall generators with thickness of mica between 30 and 50 μ were made. Films of HgTe thicker than 3 μ are remarkably less elastic and are easily broken during bending. Because of this reason only films thinner than 3 μ were considered in this paper. On the basis of the HgTe films properties the parameters of the Hall-generators as the function of thickness were determined. These were: sensitivity of Hall generator defining the slope of the static characteristic γ' = ( U yH / I x bdB) (V/A kG), sensitivity defining maximal output voltage of Hall generator γ' = ( U yHmax/ B)( μV/G) and the power coefficient defined as p yH = ( P yH / B 2) for the assumption, that the length to width ratio of Hall-generator is ( a/ b) = 2. The obtained results show that the sensitivity γ varies monotonically from a value of 15 V/A kG for c = 0·1 μ to the value of 0·40 V/kG for c = 3 μ, and the sensitivity γ' changes also monotonically from 49 to 38 μV/Gs respectively (for the assumption of the linearity of the static characteristics). On the other hand the power coefficient p yH varying from 4·1 × 10 −14 to 1·96 × 10 −11 W/ G 2 respectively. Temperature characteristics of resistivity and Hall coefficient show minimum values of coefficients: α = (1/ ρ)(d ρ/d T) and β = (1/ R H )(d R H /d T) for the film thickness about 1·3–1·5 μ. Mean values of these coefficients defined for the above mentioned thickness within the temperature range between 0 and 100°C are as follows: α = −0·04%/° C and β = −0·22%/°C. For extreme thicknesses the coefficients α and β reach the mean values of −0·1 to −0·25%/°C and −0·40 to −0·50%/°C respectively.

Zum aufbau der sperrschichten in kaltleitendem bariumtitanat

The anomalous rise in resistance with rising temperature in doped barium titanate is caused by barrier regions at the grain boundaries. These can be purposefully controlled by variation in the conditions of production. In particular, it was possible to produce a new cold conductor by concentrating the doping agent (Sb) in the grain boundaries for which a rise in resistance up to a factor of 10 7 could be achieved. The resistance-temperature characteristic of these cold conductors which deviates from the usual curves can be explained in full detail within the range of the barrier region models used so far from the varying structure of the barrier regions at the grain boundaries.

Electrical conduction in irradiated pyrolytic graphite

Fast neutron irradiation at about 20°C to a dose of 1018 neutrons per cm2 reduces the a-axis conductivity of recrystallized pyrolytic graphite by a factor of about 3.1, but increases the c-axis conductivity by a factor of about 5.2. Using the conductivity in these two directions as an indicator, the annealing behaviour has been studied by a combination of isochronal and isothermal techniques up to 1350°C. The annealing kinetics found are similar to data reported for reactor grade graphite, but data on the resistivity-temperature characteristics for various degrees of residual damage are found to be useful in discussing the electrical properties of disordered pyrolytic graphites. In particular it appears that interestitial atoms assist conduction in the c-axis, but reduce a-axis conductivity up to 800°K, whereas vacancies exert a dominant effect only below 400°K.

Processing Techniques and Applications of Positive Temperature Coefficient Thermistors

Thermistors with positive temperature characteristics of resistance have been recently developed. Their distinguished temperature characteristics, being divided into two groups--type SW and TC--have various application fields in electronic and electrical engineering. The paper describes and surveys the processing techniques of major importance, the fundamental characteristics of this component, and design criteria for the desired component. Various uses of the component, as a thermal controller, a current limiter, a current stabilizer, a temperature compensator, etc., are explained to serve as a guide to other applications.

Resistance Strain Gauges for the Measurement of Steady Strains at High Temperatures

The paper reviews the principal aspects of an investigation carried out between 1958 and 1962 in order to develop a wire resistance strain gauge for the measurement of steady stresses in stationary and rotating turbojet components operating at temperatures up to 600°C in oxidizing atmospheres. The characteristics of a number of alloys are reviewed and the behaviour of long unbonded wires drawn from nickel-chromium, iron-chromium-aluminium and platinum-tungsten alloys are discussed in detail. The effect of such factors as annealing, ordering and oxidation of the alloy's lattice on the resistance-temperature characteristics of the wire are considered. On the basis of such findings three alloys are selected for test in the form of flat grid strain gauges. The results obtained from a large number of such gauges over periods of time in excess of 200 hours are presented. It is concluded that only wires having low temperature coefficients of resistance and oxidation rates, as well as a high degree of stability, are suitable for the manufacture of strain gauges for the measurement of steady strains. Provided they were suitably heat-treated, some alloys of the nickel-chromium-aluminium, iron-chromium-aluminium and platinum-tungsten systems appeared suitable and the results obtained under typical laboratory and field conditions are presented. In general it appeared possible to prepare strain gauges having a temperature coefficient of resistance corresponding to an apparent strain of less than 30 μin/in degC (900 lb/in2 in steel) and a time-induced drift of less than 3 μin/in h (90 lb/in2 in steel). The accuracy of the measurements is therefore largely dependent upon the accuracy to which temperature compensation may be effected. A number of temperature compensating circuits are examined as well as the effect of such factors as current heating, stray magnetic fields and joints on the final accuracy. The shear strength and insulation resistance are given for a number of adhesives and cements chosen because of their compatibility with the strain gauge filaments.

The role of glass in chemical analysis

The availability of various types of glass in the form of laboratory ware and the ease of fabrication of glass into special apparatus provides a valuable aid to the analytical chemist in many ways. Simple composition, good chemical durability and good thermal shock properties have made borosilicate glass a leader in general analytical applications. 96% silica glass has all the advantageous properties of borosilicate glass plus excellent thermal shock resistance and high service temperature characteristics. Other glasses, such as alkali resistant glass, low actinic glass, and aluminosilicate glass, are unique in their properties of good durability to alkaline solutions, absorption of ultraviolet light, and high service temperature respectively. Glasses with tailored optical transmittance or thermal expansions characteristics are useful in special applications. Progress in any field of science is dependent on the tools available for experimentation and glass, because of its versatility and flexibility, plays a vital role as an important laboratory implement for the analytical chemist.

American Society for Testing Materials‐National Meeting

TWENTY years ago, there was no commercial production of metal‐to‐metal adhesive‐bonded structures, and much of the recent progress has resulted from a greater understanding of the molecular physics of the adhesive mechanism. Theoretical and experimental knowledge of the fundamentals of adhesion was reviewed as was experimental work in Germany on metal‐to‐metal adhesives. The European aircraft industry has put heat‐curing resins to general use. German research, however, has also covered room‐temperature‐curing adhesives which are specially valuable for repairs in the field. Since work in the United States has been confined largely to heat‐curing adhesives, the German work on room‐tempcrature‐curing adhesives was of considerable interest. Most of the metal‐to‐metal bonding adhesives used today are phenolic or epoxy‐modificd phenolic types. These, however, will withstand only short‐time exposure to temperatures above 500 to 1,000 deg. F. Prolonged high temperatures break down the polymer structure and drastically lower strength. Research was described in which an inorganic component (most satisfactory to date: arsenic pentoxide) was added to the organic adhesive to provide thermal resistance. Results definitely indicated that organic‐inorganic adhesive systems provide one solution to the thermal resistance problem. The high temperature resistance characteristics of five ceramic adhesives were presented. These inorganic adhesives were prepared as ceramic frits and applied to stainless steel, the material being considered for wings and control surfaces of missiles. Data from tests at 800 and 1,200 deg. F. showed great promise for this type of adhesive.

示差熱分析の応用に関する研究 (第1報)

In order to examine thermal change of organic medicinals during heating, a very simple differential thermal analyzer was devised, utilizing the large temperature-resistance characteristics of a thermister. An AC voltage was applied to the thermister and voltage deviation between thermisters on the objective control substance and sample sides was amplified and measured. Sodium chloride was used as the standard and the amount taken was 300mg. of both sodium chloride and sample. Temperature rise was of 1°/min., and 1V was applied to the bridge. Thermal analyses were carried out on citric acid, sodium citrate, and calcium lactate as the hydrated organic medicinals and they all indicated distinct heat absorption by liberation of the water of crystallization. It was also observed that calcium lactate absorbed heat on transiting to amorphous state after liberation and evaporation of the water of crystallization.

A Copper Resistance Temperature Scale

Fine commercial copper wire, attached with Formel varnish to a copper base, has sufficiently stable and reproducible resistance temperature characteristics to be used as a resistance thermometer in the temperature range 20°–320°K. Excellent thermal contact is achieved by this construction; hence, unusually large heat inputs to the thermometer can be tolerated. Resistance and temperature coefficient of resistance are tabulated and limitations of accuracy discussed.