Temperature calibration material

McGhie et al. (53, 54) proposed a new temperature calibration technique in which a small inert platinum weighl is suspended within the thermo-balan ce sample container by a fusible link composed of a temperature calibration material. When the temperature exceeds the fusible link melting point, the platinum weight is released. The weight is either caught in the sample container, producing an action/reaction response on the TG curve,... 

These temperature calibration materials are supplied by instrument manufacturers on request. The essential condition is that the material should be pure. The above data are generally available for determination of temperature on DTA or DSC equipment. 

Mills has concluded in his review article on molten slags that (1) most viscosity measurements were subject to experimental imcertainties of 25% (2) in some cases experimental uncertainties could be > 50% and (3) experimental uncertainties as low as 10% could be achieved by careful calibration of viscometers with high and low temperature reference materials. 

Experiments were conducted in a large (-26 m3) radon/thoron test facility (RTTF) designed for calibration purposes and simulation studies (Bigu, 1984). A number of different materials were exposed in the RTTF to a radon/radon progeny or thoron/thoron progeny atmosphere. Exposure of the materials was carried out under laboratory-controlled conditions of radiation level, aerosol concentration, air moisture content and temperature. The materials used were in the form of circular discs of the same thickness (-0.5 mm) and diameter (-25 mm), and they were placed at different locations on the walls of the RTTF at about 1.6 m above the floor. Other samples were placed on horizontal trays. Samples (discs) of different materials were arranged in sets of 3 to 4 they were placed very close to one another to ensure exposure under identical conditions. Exposure time was at least 24 hours to ensure surface activity equilibrium, or near equilibrium, conditions. 

The calibration of DTA systems is dependent on the use of appropriate reference materials, rather than on the application of electrical heating methods. The temperature calibration is normally accomplished with the thermogram being obtained at the heating rate normally used for analysis [16], and the temperatures... 

This latter point begs the question Who can verify the accuracy of a reference point if its value may vary In other words, who is the ultimate source of calibration materials, such as a thermometer In the U.S., it is the National Institute of Standards and Technology (NIST). This is the same organization that we cited as the source of accurate standardization materials in Chapters 3 and 4. Experiments 16 and 17 in this chapter are exercises in the calibration of a temperature sensor and how such a calibrated sensor can be used. 

Another way to calibrate temperatures in NMR spectroscopy consists of investigating materials that lead to signals with temperature-dependent chemical shifts (shift thermometers). For the development of shift thermometers, the temperature-dependent chemical shift is compared with the occurrence of melting and phase transitions, allowing a temperature calibration with high accuracy over a broad temperature range. 

Melting Points and Phase Transition Temperatures of Materials Used for the Calibration of NMR Probes at Elevated Temperatures (8)... 

To calibrate the pixel sensitivities black body radiation is usually measured at different temperatures. Since a black body has an emissivity of 1 at every position, variations in detector pixel sensitivities are eliminated by a calibration function. As this IRT-method should be used here to quantify very small heat signals on combinatorial libraries with diverse materials, differences in emissivities have to be considered. Most materials are grey bodies with individual emissivities less than 1. Therefore, the calibration was not performed with a black body but with the library, as described before, a procedure that corrects not only for pixel sensitivity but also for emissivity differences across the library plate [5]. For additional temperature calibration, the IR-emission of the library is recorded at several temperatures in a narrow temperature window around the planned reaction temperature. By this procedure, emissivity changes, temperature dependence and individual sensitivities of the detector pixels can be calibrated in one step. After this... 

This third component corrects for errors associated with the use of 20 °C calibrated material in 20 3 °C solutions. When two consecutive volumetric operations are performed at the same temperature, as is the case in dilution stages, they become self-corrected for this effect. 

Thermal analysis systems require calibration prior to routine use. In TGA, calibration for mass is carried out by calibrating the microbalance using a set of standard weights, as for any balance system. Temperature calibration is effected by measuring the Curie point temperatures of a suite of International Confederation for Thermal Analysis and Calorimetry (ICTAC) Certified Reference Materials, which have well-defined Curie points. ... 

This temperature calibration does not take into account thermal lag (and therefore temperature gradients) within the sample, one of the arguments put forward to support the use of organic materials to temperature-calibrate a DSC for pharmaceutical measurements. However, the poor availability of pure and certified organic temperature standards of sufficient accuracy is a powerful argument against using such materials. 

Many spectrometers are equipped with facilities to monitor and regulate the temperature within a probe head. Usually the sensor takes the form of a thermocouple whose tip is placed close to the sample in the gas flow used to provide temperature regulation. However, the readings provided by these systems may not reflect the true temperature of the sample unless they have been subject to appropriate calibration. One approach to such calibration is to measure a specific NMR parameter that has a known temperature dependence to provide a more direct reading of sample temperature. Whilst numerous possibilities have been proposed as reference materials [41], two have become accepted as the standard temperature calibration samples for solution spectroscopy. These are methanol for the range 175-310 K and 1,2-ethanediol (ethylene glycol) for 300-400 K. 

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