Title :
A differential interface for trace moisture sensor
Author :
Khan, Anwar Ulla ; Islam, Tarikul ; Akhtar, Jamil
Author_Institution :
Electr. Eng. Dept., Jamia Millia Islamia, New Delhi, India
Abstract :
The proposed interface is a capacitance to frequency convertor (CFC), which is simple and effective solution for reading capacitive difference between the sensor capacitance and reference. The output is a square wave signal, where the signal frequency is proportional to the sensor differential capacitance. Proposed interface integrates the advantage of two basic measurement techniques, bridge and oscillator, provides accurate and digital output in the form of pulses. Initially, experiments and analysis have been performed with discrete ceramic capacitance and then to assure the effectiveness of the circuit, a capacitive humidity sensor based on sol-gel thin film porous γ-Al2O3 has been used. In trace moisture (10-100ppm) measurement capacitance difference of the sensor is very small in the range of few pF, requires measurement of differential capacitance. Proposed circuit is insensitive to stray capacitance between sensors nodes and ground and feature high resolution and excellent linearity as well as compatible with microcontroller. The effect of central frequency on the sensitivity of the circuit has also been analyzed.
Keywords :
aluminium compounds; bridge circuits; capacitance measurement; capacitive sensors; ceramics; humidity measurement; humidity sensors; oscillators; porous materials; sol-gel processing; thin film sensors; Al2O3; CFC; bridge; capacitance to frequency convertor; capacitive humidity sensor; differential capacitance measurement; differential capacitance sensor; differential interface; discrete ceramic capacitance; microcontroller; oscillator; sol-gel thin film porous material; square wave signal frequency; trace moisture measurement; trace moisture sensor; Bridge circuits; Capacitance; Capacitive sensors; Frequency conversion; Humidity; Moisture; Moisture measurement; active bridge; capacitance to frequency convertors; capacitive sensor; humidity sensor; relaxation oscillator;
Conference_Titel :
Signal Processing, Informatics, Communication and Energy Systems (SPICES), 2015 IEEE International Conference on
Conference_Location :
Kozhikode
DOI :
10.1109/SPICES.2015.7091527