Temperature-Phase Converter Based on a LC Cell as a Variable Capacitance

Sensors

Juan Carlos Torres¹  Braulio Garc໚-Cámara²  Isabel Pérez²  Virginia Urruchi²  José Manuel Sánchez-Pena² 

[1] Displays and Photonic Applications Group, Department of Electronic Technology, Carlos III University of Madrid, Avenida de la Universidad 30, Leganés E28911, Spain;

关键词: nematic liquid crystal;    impedance analysis;    temperature dependence;    equivalent circuit;    capacitive sensor;    simulation;   

DOI  :  10.3390/s150305594

来源: mdpi

【 摘 要 】

The main characteristic of liquid crystals is that their properties, both electrical and optical, can be modified through a convenient applied signal, for instance a certain voltage. This tunable behavior of liquid crystals is directly related to the orientation of their nanometric components with respect to a director direction. However, the initial alignment is a fabrication-dependent parameter and may be either planar or homeotropic. In addition, the strong dependence of the properties of liquid crystals with the temperature is well known and widely used for several temperature sensors. This dependence is produced by the influence of the temperature on the ordering of the molecules. In this work, we have studied the temperature dependence of the electric properties of a liquid crystal cell, in particular the dielectric permittivity, with the temperature as a function of the initial alignment set during the fabrication process. Starting from experimental measurements, an equivalent circuit model including the temperature dependence has been proposed. We have observed that a good linearity in a wide temperature range is provided at a suitable exciting frequency. Finally, a proper conditioner circuit is proposed as a powerful tool for linear and high sensibility temperature measurement.

【 授权许可】

CC BY   
© 2015 by the authors; licensee MDPI, Basel, Switzerland.