Limits...
Temperature-frequency converter using a liquid crystal cell as a sensing element.

Marcos C, Sánchez Pena JM, Torres JC, Isidro Santos J - Sensors (Basel) (2012)

Bottom Line: The variation of the dielectric permittivity with temperature is used to modify the capacitance of a plain capacitor using a LC material as non-ideal dielectric.The output frequency is related to the temperature of LC cell through the equations associated to the oscillator circuit.The experimental results show excellent temperature sensitivity, with a variation of 0.40% of the initial frequency per degree Celsius in the temperature range from -6 °C to 110 °C.

View Article: PubMed Central - PubMed

Affiliation: Departamento de Tecnología Electrónica, Universidad Carlos III de Madrid, Madrid, Spain. cmarcos@ing.uc3m.es

ABSTRACT
A new temperature-frequency converter based on the variation of the dielectric permittivity of the Liquid Crystal (LC) material with temperature has been demonstrated. Unlike other temperature sensors based on liquid crystal processing optical signals for determining the temperature, this work presents a system that is able to sense temperature by using only electrical signals. The variation of the dielectric permittivity with temperature is used to modify the capacitance of a plain capacitor using a LC material as non-ideal dielectric. An electric oscillator with an output frequency depending on variable capacitance made of a twisted-nematic (TN) liquid crystal (LC) cell has been built. The output frequency is related to the temperature of LC cell through the equations associated to the oscillator circuit. The experimental results show excellent temperature sensitivity, with a variation of 0.40% of the initial frequency per degree Celsius in the temperature range from -6 °C to 110 °C.

Show MeSH
Experimental setup for the temperature-frequency converter.
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC3376606&req=5

f6-sensors-12-03204: Experimental setup for the temperature-frequency converter.

Mentions: The temperature-frequency converter has been implemented based on Figure 3(b) as a multivibrator circuit. A TL081 general purpose operational amplifier has been used. The feedback resistors, R1 and R2, and the charging resistor, R, take appropriate values to set an output signal frequency of 5 kHz. With this working frequency, the electric behavior of the NLC cell can be assumed as a pure capacitance. The experimental setup implemented for the NLC SWG temperature sensor is shown in Figure 6.


Temperature-frequency converter using a liquid crystal cell as a sensing element.

Marcos C, Sánchez Pena JM, Torres JC, Isidro Santos J - Sensors (Basel) (2012)

Experimental setup for the temperature-frequency converter.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3376606&req=5

f6-sensors-12-03204: Experimental setup for the temperature-frequency converter.
Mentions: The temperature-frequency converter has been implemented based on Figure 3(b) as a multivibrator circuit. A TL081 general purpose operational amplifier has been used. The feedback resistors, R1 and R2, and the charging resistor, R, take appropriate values to set an output signal frequency of 5 kHz. With this working frequency, the electric behavior of the NLC cell can be assumed as a pure capacitance. The experimental setup implemented for the NLC SWG temperature sensor is shown in Figure 6.

Bottom Line: The variation of the dielectric permittivity with temperature is used to modify the capacitance of a plain capacitor using a LC material as non-ideal dielectric.The output frequency is related to the temperature of LC cell through the equations associated to the oscillator circuit.The experimental results show excellent temperature sensitivity, with a variation of 0.40% of the initial frequency per degree Celsius in the temperature range from -6 °C to 110 °C.

View Article: PubMed Central - PubMed

Affiliation: Departamento de Tecnología Electrónica, Universidad Carlos III de Madrid, Madrid, Spain. cmarcos@ing.uc3m.es

ABSTRACT
A new temperature-frequency converter based on the variation of the dielectric permittivity of the Liquid Crystal (LC) material with temperature has been demonstrated. Unlike other temperature sensors based on liquid crystal processing optical signals for determining the temperature, this work presents a system that is able to sense temperature by using only electrical signals. The variation of the dielectric permittivity with temperature is used to modify the capacitance of a plain capacitor using a LC material as non-ideal dielectric. An electric oscillator with an output frequency depending on variable capacitance made of a twisted-nematic (TN) liquid crystal (LC) cell has been built. The output frequency is related to the temperature of LC cell through the equations associated to the oscillator circuit. The experimental results show excellent temperature sensitivity, with a variation of 0.40% of the initial frequency per degree Celsius in the temperature range from -6 °C to 110 °C.

Show MeSH