A new method of temperature measurement using thermochromic liquid crystals (extension of measurable range based on spectral intensity in the narrow-band wavelength)

This paper describes the extension of the measurable range of temperature measurement using thermochromic liquid crystals (TLCs). In the proposed method, the temperature is uniquely determined by measuring only a single optical parameter: the spectrum intensity of the scattered light at a specific wavelength. In the first stage of the study, the relationship between the spectrum intensity of the scattered light at the TLC and temperature of the heat transfer surface was investigated. It was found that a white LED had more favorable features than a halogen lamp, and thus was suitable as a light source for the proposed method. Using the white LED, the range of the measurable temperature achieved by the proposed method, 27-60 degrees C, was approximately three times as broad as that by conventional methods that use mapping of the color change of TLCs, 32-42 degrees C. In the second stage, the proposed method was applied to measurement of the two-dimensional temperature distribution over a planar heat-transfer solid surface. The range of the measurable temperature with a temperature resolution of 0.1 degrees C was found to be 28-46 degrees C, which is approximately twice as broad as that by conventional methods using TLCs, 32 42 degrees C. (C) 2015 Elsevier Ltd. All rights reserved.