Errors in thermochromic liquid crystal thermometry

Abstract

This article experimentally investigates and assesses the errors that may be incurred in the hue-based thermochromic liquid crystal thermochromic liquid crystal (TLC) method, and their causes. The errors include response time, hysteresis, aging, surrounding illumination disturbance, direct illumination and viewing angle, amount of light into the camera, TLC thickness, digital resolution of the image conversion system, and measurement noise. Some of the main conclusions are that: (1) The 3 ϫ 8 bits digital representation of the red green and blue TLC color values produces a temperature measurement error of typically 1% of the TLC effective temperature range, (2) an eight-fold variation of the light intensity into the camera produced variations, which were not discernable from the digital resolution error, (3) this temperature depends on the TLC film thickness, and (4) thicker films are less susceptible to aging and thickness nonuniformities.

Vortex tracking on visualized temperature fields in a rotating Rayleigh–Bénard convection

“…Relatively large deviations appear for temperatures larger than 26 • C and are caused by irregular, spiky scatters of hue values. In the analysis, such spiky noise will be removed by median filtering that was also used to overcome general noise arising from TLCs (Wiberg and Lior (2004); Rao and Zang (2010)) as detailed in the sections below.…”

“…Additionally, under the condition P r ≥ O(1), vortex motions can be captured on temperature fields. In measurements of the temperature field using TLCs, however, multiple factors introducing uncertainties have been reported (Wiberg and Lior (2004); Rao and Zang (2010)), e.g., non-uniform incidence of illumination light, aging of TLCs, and etc. We thus have to consider the effect of relatively large uncertainties on measurements.…”

In Situ Growth Measurements of Sodium Sulfate during Cooling Crystallization

“…The transient response time of the TLC sheets is of the order of 100 ms 20. In order to be fast enough to capture the transients of the growth phase, it is only necessary that the characteristic time scale for the growth of the sodium sulfate crystal is slower than 100 ms. Lindenberg 21 developed a method to calculate the characteristic time scale for crystal growth and found it to be between 1 and 100 s for a range of organic and inorganic salts.…”

Thermochromic Behavior of a Novel Nematic Liquid Crystal Mixture: Effects of Chiral Doping

“…The RGB model is a model used for describing colors generated additively, as is the case on a monitor screen. RGB images, also referred to as true-color images, can contain up to 16 Fig. 2(a).…”

“…[12][13][14] Light reflection has been used in thermochromic liquid crystal temperature measurements but its main disadvantage is that the correlating equation for temperature is sensitive to light intensity, lighting type and viewing angle. 15,16 In addition, while the CLC materials display color over its entire active range, the reflection calibration generally utilizes only 25-50% of this range. 10 The light transmission properties of liquid crystals are used extensively in liquid crystal display technology, 17 however, little work has been done to characterize and understand the effects of temperature on the light transmission properties of induced CLCs for sensing applications.…”