Interlaboratory Comparison of Reference Surface Temperature Apparatus at NMIs

During 2001 and 2002, the first international comparison of surface temperature measurements at national metrology institutes (NMIs) was organized under EUROMET Project No 635. The coordinator for this project was the National Office of Measures (OMH) in Hungary. Among the participants were the Swedish National Testing and Research Institute (SP) from Sweden, the Centre for Metrology and Accreditation (MIKES) in Finland, and Justervesenet (JV) in Norway. The comparison showed a need for better apparatus to reduce the differences in the results from the different laboratories. As a result, a new apparatus was designed at SP and MIKES made some changes to their apparatus. To test the new and modified apparatus, SP took the initiative to arrange and coordinate a new comparison. In this recent comparison, measurements were made at temperatures from 50 to 300°C on surfaces of aluminum and stainless steel. The comparison was arranged and performed during 2005 and 2006. Participants in the comparison were OMH, MIKES, RISOE, JV, and SP. The comparison results using the newly developed apparatus show improved agreement with the earlier EUROMET intercomparison, but also indicate a need for a more standardized calibration method and apparatus to be able to perform calibrations in different laboratories with good agreement.     

Refractive index measured by laser beam displacement at λ=1064 nm for solvents and deuterated solvents

The refractive index of a liquid is determined with 0.0003 accuracy from measurements of laser beam displacement by a liquid-filled standard 10 mm spectrophotometer cell. The apparatus and methods are described and the results of measurements at λ=1064 nm and T=25.0 °C for 30 solvents and deuterated solvents are presented. Several sources of potential systematic errors as large as 0.003 are identified, the most important being the curvature of the liquid cell windows. The measurements are analyzed accounting for the significant imperfections of the apparatus.     

Realization of the 3He Vapor-Pressure Temperature Scale and Development of a Liquid-He-Free Calibration Apparatus

The ³He vapor-pressure temperature scale was realized using an apparatus based on a continuously operating ³He cryostat at the National Metrology Institute of Japan (NMIJ), National Institute of Advanced Industrial Science and Technology (AIST). The cryostat has two operational modes: a ³He circulation mode and a 1 K pot mode. The ³He circulation mode can be used for ³He vapor-pressure measurements below 1.6 K, and the 1 K pot mode can be used for measurements above 1.3 K. Either mode can be selected for measurements from 1.3 K to 1.6 K. The realization of the ³He vapor-pressure temperature scale in this study fully covers its defined temperature range from 0.65 K to 3.2 K in the International Temperature Scale of 1990. The latest realization results are presented in this article. In addition, a liquid-He-free calibration apparatus was developed. It does not require liquid helium as a cryogen, which usually entails cumbersome handling and periodic refilling. The apparatus was designed for the calibration of capsule-type resistance thermometers from 0.65 K to 24.5561 K (the triple point of neon). The cooling system of the apparatus consists of a commercially available pulse-tube refrigerator and a ³He Joule?CThomson (JT) cooling circuit developed at NMIJ/AIST. The pulse-tube refrigerator is used in a pre-cooling stage and cools the apparatus to approximately 5 K. The ³He JT cooling circuit is used to cool the apparatus from 5 K to below 0.65 K. Since the ³He JT cooling circuit is a closed circuit, the apparatus can run continuously with only simple maintenance required. The basic characteristics of the apparatus are described.     

A modified Auger system for Auger electron appearance potential spectroscopy

We present an apparatus for Auger electron appearance potential spectroscopy measurements derived from a conventional Auger electron spectrometer. This non-dispersive apparatus is shown to be very sensitive with a high spatial resolution. The utility of the technique has been tested by measuring the 2P levels for some 3d transition metals.     

On-line measurement of the thickness and optical quality of float glass with a sensor based on a diffractive element

An on-line apparatus for accurate measurement of float-glass thickness and edge distortion was built and tested in industrial environments. The intelligent part of the sensor is a diffractive optical element. The theory and construction of the apparatus are described, and data from on-line measurements are presented.     

An Absolute Viscometer-Densimeter and Measurements of the Viscosity of Nitrogen, Methane, Helium, Neon, Argon, and Krypton over a Wide Range of Density and Temperature

An apparatus for the simultaneous measurement of viscosity and density of fluids is presented. The viscometer-densimeter covers a viscosity range up to 150 µPas and a density range up to 2000 kgm^–3 at temperatures from 233 to 523 K and pressures up to 30 MPa. Very accurate density measurements with uncertainties of ±0.02 to ±0.05% have always been carried out with this apparatus, although in its first version it was necessary to calibrate the viscosity measuring system on a reference fluid in order to achieve uncertainties of ±0.6 to ±1.0% in viscosity. After significant improvements, the apparatus now achieves uncertainties in viscosity of less than ±0.15% in the dilute gas region and less than ±0.4% for higher densities. Moreover, the viscosity measuring system can be described in an absolute way; calibration is no longer necessary. In order to test the advanced apparatus and to determine viscosity-density values of very high quality, comprehensive measurements on nitrogen, argon, and methane were carried out in the entire working range of the viscometer-densimeter. In addition, viscosity-density measurements on helium, neon, and krypton were made on two selected isotherms each. All measurements show that the estimated total uncertainty of ±0.15 to ±0.4% in viscosity and of ±0.02 to ±0.05% in density is clearly met. In order to verify the results of the combined viscometer-densimeter, a new apparatus for very accurate viscosity measurements was designed. While the working range of this apparatus is restricted to the dilute gas region, it yields uncertainties of less than ±0.07% in viscosity. Measurements carried out with this apparatus confirmed the previously measured values of the combined viscometer-densimeter within ±0.03%.     

Fourier Analysis From Networked Measurements Using Time Synchronization

Can frequency-domain analysis be made from time-domain measurements taken over networks with poor temporal characteristics, that is, poor or no guarantees about when commands or data will be delivered, such as the public Internet? Our answer to this question is ldquoyes.rdquo Provided that the times that samples are taken are measured accurately, Fourier analysis can be performed, even when the samples are taken at nonuniform intervals. Due to the tendency of packet delays in networks to have long-tailed probability distributions, it is also desirable not to make assumptions concerning the probability distribution of the time intervals between samples. We show that the combination of network time synchronization and stabilization of measurement apparatus using the IEEE 1588 Protocol and the methods for Fourier analysis of nonuniformly spaced data from the literature are sufficient to provide spectra from measurements taken with networked sensors. The key steps of our method are an accurate timestamping of the measurements followed by a Fourier transform. The Fourier transform may be accomplished by either resampling the measurements into a constant rate so that fast Fourier transforms may be used or performing a least squares fit of a sine/cosine basis to the data. Both approaches were tested using measurements taken over the public Internet using measurement apparatus synchronized using IEEE 1588.     

The International Commission for Optics

An apparatus is described that automatically measures the course of the accommodation of the human eye with infra-red light. The principle of measurement is based on the spreading of the image of a test target on the retina when the eye is defocused. The measuring technique is an autocollimating one. Each single measurement tests the state of accommodation over a range from ?7 to +2 D. Targets with a complicated structure such as gratings can be used to get a better criterion for defocusing. The apparatus gives 50 measurements of accommodation per second. Compared to the slow changes of accommodation this is an effectively continuous registration. The lag of accommodation and the transfer function of accommodation computed from the response to a sudden shift in target distance were measured with the apparatus.     

Development of a method and apparatus for measuring the light-reflecting characteristics of infrared optoelectronic systems

Questions related to the study of the light-reflecting characteristics of optoelectronic systems that function in the infrared domain are considered. A method and combined structural and functional optical apparatus scheme is proposed that makes it possible to perform measurements of the light-reflecting characteristics of modern infrared devices; a mathematical apparatus for processing the measurement results is also proposed. The expected value of the error of such measurements is determined. __________ Translated from Izmeritel’naya Tekhnika, No. 9, pp. 24–28, September, 2007.     

Force Transmission Error Analysis for a High-Pressure Single-Sinker Magnetic Suspension Densimeter

The magnetic suspension densimeter (MSD) is a sophisticated, state-of-the-art device that provides extremely accurate results for density measurements. The MSD uses a magnetic technique to couple a mass inside a measurement cell with an external mass balance for mass measurement. This article presents a force transmission error (FTE) analysis for a high-pressure, single-sinker MSD. Due to the magnetic working principle of the apparatus, magnetic properties of the high-pressure cell and external magnetic fields affect the measurements slightly. For the analysis, McLinden et al. suggest making measurements using two different sinkers, a titanium sinker and a copper sinker, having the same mass. The measurements cover densities for methane, ethane, carbon dioxide and nitrogen over the temperature range from 265 K to 450 K (±5 mK stability) up to 180 MPa (uncertainty of 0.01 % full scale: 200 MPa). Comparing and manipulating the measurements permit determination of apparatus and fluid specific effects that contribute to the FTE. For this MSD, the apparatus effect is about 200 ppm, which effectively masks any fluid specific effect. A comprehensive analysis of the FTE produces a uniform deviation for density values of about 0.05 % at 2σ across the full range of pressure.     

A Contactless CCD Dilatometer for Foil Materials

A contactless, compact, low-cost dilatometer based on a laser-pulse thermal-conductivity apparatus has been developed to measure the linear thermal expansion of foil materials. The two sample-edge images are projected onto the array of a charge-coupled device (CCD). Changes in sample length are determined from measurements of the corresponding displacements of the sample-edge images focused on the CCD. The dilalometer performance was tested by comparing results of measurements of the thermal expansion for pure copper with published data. The linear thermal expansion of an L-16-type foil of 20-m thickness, which is a candidate material for thermocontrol layers (in engineering), was measured with the apparatus.     

A New Computer-Aided Apparatus for Simultaneous Measurements of Water Uptake and Swelling Force in Tablets

Abstract

Water uptake and disintegrating force development have frequently been related to tablet disintegration properties.

Water penetration into compressed tablets has been studied by many authors using modified Enslin apparatus. Meanwhile, in previous papers by our group, a great deal of attention has been paid to the measurements of disintegrating force and to the kinetics of force development.

Given the fact that water penetration and swelling force development are related to each other, a new apparatus was set up which allows simultaneous measurements of water penetration and force development. It consists of a modified apparatus for force measurements, integrated with a modified Enslin apparatus. Both force and water uptake data were collected by a computer and stored for subsequent analysis.

Fitting of both water penetration and force development curves was performed with a commercially available software package for non-linear regression analysis.

This enables an examination of the relationships between force development and water penetration on the basis of homogeneous rate parameters. The apparatus was validated on a model tablet formulation based on dicalcium phosphate dihydrate with carboxymethylstarch.

Besides application in fast disintegrating tablets, this approach could be useful to study the behaviour of swelling-controlled release systems, in which the release mechanism (swelling force) is triggered by water penetration.     

The maximum experimental safe gap: Comparison of results from 8-litre and 20-cm3 explosion vessels

Maximum Experimental Safe Gap measurements in the 20-cm³ and 8-1 apparatuses are compared for some oxygen-enriched fuel-air mixtures. For a given fuel, a discontinuity in the curves of MESG against nitrogen content is observed in both the 20-cm³ and the 8-1 apparatus results, but occurs at higher nitrogen content in the larger apparatus. Thus with some mixtures, the MESGs measured in the 20-cm³ apparatus differ considerably from the values measured in the 8-1 apparatus.These differences are qualitatively explained with reference to the changes that occur in the properties of the hot jet ejected through the flame-path as the internal explosion pressure increases.     

The Limits of a Rayleigh-Scattering Primary Thermometer

Progress in the development of an apparatus to compare the thermodynamic temperature of a gas with the temperature as determined by the International Temperature Scale of 1990 (ITS-90) is reported. The apparatus uses the Rayleigh scattering of light from a gas to provide an intensive measure of gas density, thus avoiding the need for corrections for dead volumes or wall adsorption required by conventional gas thermometry. A laser beam is shone through gas in two cells that are at the same pressure but different temperatures, and the measured ratio of the Rayleigh scattering signals from the two cells can be related to the ratio of the gas density in the cells. From the density ratio, the thermodynamic temperature of one cell can be inferred if the other cell is held close to the triple point of water. However, the Rayleigh scattering is weak and signals are small, making measurements with sufficiently small uncertainty extremely challenging. Since previous reports, the apparatus has been significantly modified, and these changes are described along with indicative results. In this paper, results of measurements in the range from 211 K to 292 K using both argon and xenon are reported. The results suffer from large systematic errors due to contamination in one of the measurement cells. Although the results do not provide reliable estimates of T  − T ₉₀, they indicate that measurements with uncertainties below 1 mK are feasible.     

A high-accuracy dilatometer for the range −20 to 700°C

We have constructed a linear-thermal expansion apparatus that employs a potassium-loaded heat pipe to provide a homogeneous temperature environment for the sample and utilizes the Merritt-Saunders (optical interferometric) method of observing its expansion. The apparatus is similar in many respects to one described previously. Temperature regulation and measurement are accomplished through the use of a dedicated laboratory microcomputer operating with a simple program. Two platinum resistance thermometers, read automatically by a digital resistance bridge, provide, on command, both the temperature of the heat pipe and that of the sample chamber. Changes in sample length are determined from measurements of the corresponding changes of optical fringes from a Fizeau interferometer as recorded on film. The coefficients of thermal expansion of two Pt-Rh alloy samples determined using the present apparatus agree at the±2 ppm level with those determined for a similar sample using the previous apparatus.Paper presented at the Tenth International Thermal Expansion Symposium, June 6–7, 1989, Boulder, Colorado, U.S.A.     

Absolute Steady-State Thermal Conductivity Measurements by Use of a Transient Hot-Wire System

A transient hot-wire apparatus was used to measure the thermal conductivity of argon with both steady-state and transient methods. The effects of wire diameter, eccentricity of the wire in the cavity, axial conduction, and natural convection were accounted for in the analysis of the steady-state measurements. Based on measurements on argon, the relative uncertainty at the 95 % level of confidence of the new steady-state measurements is 2 % at low densities. Using the same hot wires, the relative uncertainty of the transient measurements is 1 % at the 95 % level of confidence. This is the first report of thermal conductivity measurements made by two different methods in the same apparatus. The steady-state method is shown to complement normal transient measurements at low densities, particularly for fluids where the thermophysical properties at low densities are not known with high accuracy.     

A high-temperature laser-pulse thermal diffusivity apparatus

A high-temperature laser-pulse apparatus for the measurement of thermal diffusivity in the temperature range from 1500 to 2500 K has been designed. constructed, and tested at the National Institute of Standards and Technology. A curve-fitting method is introduced by which the entire experimental temperature history curve is fitted with the theoretical curve under the boundary condition of radiative heat losses. The new apparatus and the curve-fitting method permit thermal diffusivity measurements with an uncertainty of not more than 3%.     

Thermal conductivity of rigid foam insulations for aerospace vehicles

The present work describes measurements of the effective thermal conductivity of NCFI 24-124 foam, a spray-on foam insulation used formerly on the Space Shuttle external fuel tank. A novel apparatus to measure the effective thermal conductivity of rigid foam at temperatures ranging from 20 K to 300 K was developed and used to study three samples of NCFI 24-124 foam insulation. In preparation for measurement, the foam samples were either treated with a uniquely designed moisture absorption apparatus or different residual gases to study their impact on the effective thermal conductivity of the foam. The resulting data are compared to other measurements and mathematical models reported in the literature.     

Development of an Apparatus for the Determination of Spectral Reflectivity at High Temperatures in the Visible

The paper presents a reflectometer for high temperature measurements. In this apparatus, the directional-hemispherical spectral reflectivity is measured by comparing the optical response of the sample to white light with the response of a reference material. The reflected light, collected by an integrating sphere, is dispersed in a spectrograph and detected by an ICCD camera. This procedure allows the simultaneous measurement of the reflectivity in a large, continuous wavelength range (presently 510 to 860 nm). An electrical resistance heater is used to heat the samples up to about 1200 K; for higher temperatures a flash-lamp pumped dye laser is used. To avoid laser induced plasma generation, the integrating sphere is placed inside a vacuum chamber, which also allows measurements under a controlled atmosphere. The response of the apparatus is calibrated to an absolute scale which allows the determination of the sample temperature by fitting the thermal emission spectrum with Planck's formula. To check the performance of the apparatus, measurements on Fe₂O₃ (hematite) and NiO have been carried out.