According to radiation temperature measurement theory, the key of temperature measurement is to choose the appropriate temperature model, which depends on the type of measured material. So how to identify the material type is significant to measure its surface temperature. Different materials have different spectral characters at the same temperature. In this paper, a method based on spectrum analysis is proposed to identify material. The spectrum of four kinds of materials is measured using Fourier transform infrared spectrometer (FTIR) at the same temperature 873K. The peak values extracted from each spectrum are used to train the identification algorithm. Then one material is chosen from the measured materials to verify the identification algorithm if the type of material can be identified. The experimental results suggest that the new method based on spectrum analyses can accurately identify the type of material.
The absorption spectra of ethylene (C2H4) located at v5+v9 band near 1626nm involve some strong peaks that are suitable for trace gas concentration detection. They are interference free from other abundant molecules that are normally present in the atmosphere. An ethylene analysis system has been developed based on the tunable diode laser absorption spectroscopy. The high resolution transmission of ethylene near 1626nm has been measured by this system under different concentration. The severe overlapping between neighboring spectral lines of ethylene is observed and they cannot be separated with each other easily under atmospheric pressure and room temperature, so a multi-peaks spectrum recognition method is proposed to separate the ethylene spectrum from other interference gas while the ethylene concentration is ultra low. A mixture of high concentration methane, low concentration ethylene with air is used to evaluate the recognition efficiency. The result shows that the ethylene line can be abstract from strong background interference using multi-peaks spectrum recognition method and the accuracy of concentration measurement can reach about 5% comparing with a mass flow meter.
The emissivity is a key parameter to measure the surface temperature of materials in the radiation thermometry. In this paper, the surface emissivity of metallic substrates is measured by the multi-wavelength emissivity measurement apparatus developed by the Harbin Institute of Technology (HIT). The measuring principle of this apparatus is based on the energy comparison. Several radiation thermometers, whose emissivity coefficients corrected by the measured emissivity from this apparatus, are used to measure the surface temperature of stainless steel substrates. The temperature values measured by means of radiation thermometry are compared to those measured by means of contact thermometry. The relative error between the two means is less than 2% at temperatures from 700K to 1300K, it suggests that the emissivity of stainless steel substrate measured by the multi-wavelength emissivity measurement apparatus are accurate and reliable. Emissivity measurements performed with this apparatus present an uncertainty of 5.9% (cover factor=2).
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