Thermometric Characteristics Research Articles

Construction and Characterization of NTC Thermistors at Low Temperature

Nano-powder of a negative temperature coefficient (NTC) ceramic with a spinel structure of Mn–Ni–Cu–Co–La–O composition was prepared by the Pechini method. A type of NTC thermistor sensor (3.0 mm diameter × 1.5 mm high) was designed by the in situ lead wire attachment method (ISAM) and made using the synthesized powder. NTC thermistors were packed in the glass-sealed package. Six independent NTC thermistors were calibrated using a cryostat, a standard platinum resistance thermometer, and a Fluke 1590 super thermometer meter over the temperature range from 18 K to 120 K. The data were interpolated to obtain calibration tables at 2 K intervals from 18 K to 30 K, and at 5 K intervals from 30 K to 120 K. These tables were fitted with the equation: 1/T = A0 + A1 ln(R/Rref) + A2 ln(R/Rref)2 + A3 ln(R/Rref)3 + A4 ln(R/Rref)4. Aging, thermometric characteristics, fitting of calibrated data, stability of NTC thermistors, and the effect of a magnetic field on NTC thermistors were investigated.

Oxidization Characteristics of Some Standard Platinum Resistance Thermometers

The oxidization characteristics of some standard platinum resistance thermometers are discussed on the basis of the Gibbs free energy diagram of the platinum-oxygen ensemble. The oxidization characteristics are estimated from the measurement of the resistance changes at the triple point of water. The resistance changes of thermometers are caused by pure chemical reactions of Pt to PtO2, PtO2 to PtO, and the deoxidization. The oxidized platinum of PtO on the platinum sensing wire does not grow directly from Pt but through PtO2. This hysteresis in the formation of PtO makes the resistance characteristics of the thermometers complicated, particularly in the range above 300 °C.

The applicability of the ITS-90 method to platinum resistance thermometers of different purity

The static characteristics of platinum resistance thermometers with different platinum purities were measured. It is shown that in the 0–420°C range the ITS-90 method gives an error of less than 0.01°C, while in the 0–230°C range the error is less than 0.006°C.

Thermometric characteristics approximation of germanium film temperature microsensors by orthonormal polynomials

Approximations of thermometric characteristics of germanium film temperature microsensors are presented using a mathematical approach based on their expansion with orthonormal polynomials. A weighted orthonormal polynomial expansion method (OPEM) is applied, involving the experimental errors of calibration test data at every point. The thermometric functions R(T) and T(R) of resistance and temperature are described in the whole temperature range (1.7–300K) and in three subintervals (1.7–20, 20–150, and 150–300K). The absolute, relative, and specific sensitivities of the sensor, as well as the main approximation characteristics, are discussed. The OPEM is extended to obtain a mathematical description of R(T) and T(R) functions by usual polynomial coefficients calculated by orthonormal ones. A comparison between maximal relative deviations of R(T) and T(R) three-interval approximations, correspondingly, by usual and orthonormal polynomials, is presented. Numerical results of the approximation parameters of these type of temperature sensors are shown in the figures and tables.

Towards new temperature standards for contactthermometry above 660 °C

In the course of a study on the behaviour of coupled heat pipes, perfect agreement has been obtainedfor the first time between measurements on the immersion characteristics in a mercury heat pipe and the Clausius-Clapeyron profile. This result opens up the perspective of using coupled heat pipes to relate thermodynamically two different temperature ranges, with the possibility of redefining one temperature range in terms of another. As a consequence, using sodium for the second heat pipe, the very high reproducibility of standard platinum resistance thermometers (SPRTs) below 400 °C can be transferred to the temperature range above 660 °C, surpassing the characteristics of high-temperature standard platinum resistance thermometers (HTSPRTs).

Structural and electrical characterisation of Mo films for transition-edge sensors

Detectors based on transition-edge thermometers are under investigation for material analysis and space observations thanks to their high-energy resolution. However, fabrication of stable structures using superconducting/normal proximity bilayer is not trivial. For example, the characteristics of thermometers made of Al/Ag are quickly degraded by interdiffusion. In this work, we report details on fabrication and characterisation of Mo films and Mo/Ag bilayers that being immiscible and non-reactive with each other should have a long time stability. First results show that bilayers with transition widths of 1 mK are achievable, adequate to realise high sensitivity thermometers.

Radiation-resistant silicon diode temperature sensors

Abstract We present a new type of silicon diode temperature sensors (DTSs) with high radiation resistance up to the dose of gamma irradiation ∼107 rad. Investigations of electrophysical and metrological characteristics of DTSs have been carried out in the range of temperatures 220–350 K and currents 10−11 to 10−2 A under gamma irradiation that allowed to reveal operating regimes with minimal influence of radiation on the device thermometric characteristics. A theoretical analytical model for the DTSs with almost ideal carrier transport has been proposed to explain the experimental behaviour of transport differential characteristics (ideality factor m, differential resistance) under irradiation. The observed non-monotonical dependencies of the ideality factor m on the current I are described well by the influence of generation–recombination and drift current components to the diffusion current of the minority carriers. The occurrence of a minimum in the m(I)-dependencies is due to a competition of these additional currents. The characteristic lifetimes of the minority carriers in the base and in the space-charge region of the diode structure have been determined. The DTSs are advanced devices with high sensitivity, accuracy, reproducibility, and easily adaptive with electronic equipment when operating in long circuits in radiation environments.

Electrical conduction in polyaniline-PMMA blends and their use as cryomagnetic temperature sensors

Electrical conduction in polymeric conductors is obscured by the presence of strong disorder. Localization and Coulomb Interactions play a dominant role. The temperature dependence of the reduced activation energy, W = dln(σ)/dln(T), shows that PAni-PMMA blends are on the metallic side of the metal-insulator transition. The temperature and field dependences of conductivity of PAni - PMMA blends are discussed. ESR line shape changes from a Dysonian with A/B ratio of about 2.5 to a Lorentzian, mirroring the temperature dependence of electrical conductivity and hence of the skin depth. Comparison with the characteristics of commercial semiconductor thermometers show that these blends can be a viable alternative to them as cryomagnetic temperature sensors.

Properties of zinc thin film thermometers

Thin films of aluminum have for many years been used near T∼1.5 K to detect the tiny temperature fluctuations which accompany the propagation of waves of third sound in thin superfluid 4He films. For lower temperatures, zinc thermometers have been used to detect phonon propagation in bulk helium. We have fabricated zinc thermometers having zero-field sensitivities δR/δT∼20000 Ω/ K at T c ∼680 mK when operated at a bias current i b =10 μA . We describe here the fabrication techniques and the operating characteristics of thin film zinc thermometers which we have used to detect third sound for 100⩽T⩽680 mK .

Non-ohmic Mott conductivity and thermometric characteristics of heavily doped silicon structures

Non-ohmic Mott conductivity and thermometric characteristics of heavily doped silicon structures

Germanium-film resistance microthermometers intended for operation within the temperature range of 0.03–300 K

Germanium-film resistance microthermometers (O1.2 × 1.0 mm) are worked out and manufactured to be used in a wide range of temperatures from superlow to room temperatures. The thermometer characteristics are investigated within the temperature range of 0.03–300 K.

Miniature temperature sensors based on Ge films

Miniature (1.2 mm diameter x 1.0 mm long) cryogenic temperature sensors have been developed. They are based on germanium films on gallium arsenide substrates and are intended to operate in a wide (0.05 K to 300 K) temperature range. Their thermometric characteristics are investigated at temperatures from 1.7 K to 300 K. A production of these sensors is organized.

Effect of platinum oxidation on the characteristics of standard platinum resistance thermometers

Platinum oxidation in PTS-10 and PTS-25 standard platinum resistance thermometers has been studied. The experimental results show that heat treatment of a thermometer at 100–300°C can increase its resistance at the triple point of water by the equivalent of 1.5 mK. A procedure for calibration in the range 0–450°C is recommended.

Thermometric characteristics of carbon fibres

Abstract The thermometric characteristics of carbon fibres obtained by the carbonization of viscose have been studied in the wide low-temperature range 300-0.3 K. It is shown that their resistance versus temperature dependences can be described by the simple formulae R ∼ 1g T and R ∼ exp( T 0 / T ) n , n

Calibration characteristics of copper resistance thermometers in the range from 77 to 273 K

Calibration characteristics of copper resistance thermometers in the range from 77 to 273 K

The characteristics of Chinese encapsulated rhodium-iron resistance thermometers

The resistance-temperature characteristics, self-heating effect and stability of a new type of Chinese encapsulated rhodium-iron resistance thermometer have been studied in the temperature range between 1.2 and 273.15 K. Resistance changes at 20 K in ten such thermometers over 30 thermal cycles between 15 and 290 K were equivalent to temperature changes of between 30 and 70 mK. The resistance against temperature characteristics of the thermometers are similar to those of standard Rh-Fe resistance thermometers and the thermometers' interchangeability characteristics are such that a one-point (273.15 K) calibration delivers a precision of 0.2 K in temperature over the range 1.2 to 273.15 K while a three-point (4.2, 77 and 273.15 K) calibration gives a precision of 22 mK below 77 K and 15 mK above 77 K.

Sensitive thermometry using capacitance variation of GaP LEDs

Red-emitting GaP LEDs are shown to provide highly sensitive temperature sensors. This investigation is based on the exploitation of capacitance variation rather than the usually employed forward voltage variation. Detailed results on thermometric characteristics are reported. A temperature variation of as low as 0.02 degree can be reliably sensed using capacitance thermometry.

Some observations on resistance/ temperature characteristics of platinum resistance thermometers

This paper seeks to highlight the unexploited potential of industrial platinum resistance thermometers by investigating calibration measurements over the range of temperature between ice-point and zinc-point. Indications are that adherence to the IPTS-68 definition might depend to a greater extent on assembling thermometers in such a manner as to realise a prescribed unique value of the coefficient δ than on requiring the temperature coefficient a to be in excess of a particular specified value. Moreover, implications arise that apparent deviations from an IPTS-68-type characteristic, and the consequent observed variability in δ, are attributable to heat conduction along thermometer stems. No attempt has yet been made to elucidate the reason for the above empirically inferred constancy of the ratio of the coefficients of terms of first and second degree in the quadratic equation relatitig resistance to the modified temperature t'. It appears that the 'fixed' correction polynomial used to convert t' into t 68 , which was defined to achieve compatibility with the thermodynamic temperature scale, represents the behaviour of a certain type of thermometer rather than of the sensing element itself; although of academic interest only, the 'bare' element would require a different, individually assigned, numerical factor in the polynomial in order to restore agreement. It might also be feasible to adopt the same procedure as a means of overcoming any discrepancy arising for a thermometer whose materials and manner of construction have resulted in a 'non-ideal' value of δ.

Interpolation procedures for ceramic-encapsulated rhodium-iron alloy resistance thermometers in the temperature range 77 to 273K

The thermometric characteristics of six ceramic-encapsulated rhodium-iron alloy resistance thermometers have been studied over the temperature range 32 to 273.15K. Data are given for the resistance-temperature relationship and the self-heating. Interpolation procedures were investigated for the range 77 to 273.15K. An eleven-term polynomial fit to many points will yield a precision of +or-0.5 mK over this range. Simpler two-point and three-point methods give a precision of +or-25 mK and +or-10 mK, respectively.

Metrological support to computerized tests on aircraft gas-turbine engines under transient conditions

Metrological support to data-acquisition systems (DAS) is improtant in providing comparability in the measured characteristics of gas-turbine engines (GTE) during development, routine production, and operation. A basic problem in the dynamic calibration of a means of measurement is to reproduce the test signal. This can be illustrated for laser systems designed for the dynamic calibration of temperature and pressure-measurement channels, which are the most widely used in testing GTE. A laser system is described that enables one to determine the amplitude, phase, transient, and pulse characteristics of thermoanemometers, resistance thermometers, and thermoelectric thermometers, including thin-wire and thin-film components, with various gas flow speeds and temperatures. This apparatus can be used in calibrating thermal transducers at frequencies up to 200 kHz with a basic error of 0.5 dB. The gas speed range is 0-200 m/sec with a maximum gas temperature of 600 degrees K. Laser methods provide dynamic calibration for pressure channels in DAS. Dynamic calibration has been applied to pressure transducers by means of a pulsed laser. The light pulse is supplied to the sensing element and produces the dynamic equivalent of a pressure pulse.