Title :
A wireless passive sensor for pH monitoring employing temperature compensation
Author :
Bhadra, S. ; Bridges, G.E. ; Thomson, D.J. ; Freund, M.S.
Author_Institution :
Dept. of Electr. & Comput. Eng., Univ. of Manitoba, Winnipeg, MB, Canada
Abstract :
We present an integrated coupled-coil passive sensor for temperature compensated remote pH monitoring. The sensor is a RLC resonant circuit consisting of an inductive coil connected in parallel to a thermistor, a varactor and a pH combination electrode. pH variation of the solution changes the voltage-dependent capacitance and shifts the resonant frequency of the sensor, while temperature change of the solution affects the resistance and changes the quality factor. The resonant frequency and quality factor of the sensor are tracked remotely by an interrogator coil coupled to the sensor coil. A temperature range of 25°C-60°C and pH over a 2-12 dynamic range can be measured simultaneously. With temperature compensation, the accuracy of the pH measurement is demonstrated to be 0.1 pH. The sensor overcomes the pH measurement error due to the temperature dependence of electrode based passive pH sensors.
Keywords :
Q-factor; RLC circuits; chemical sensors; coils; compensation; pH measurement; thermistors; varactors; wireless sensor networks; RLC resonant circuit; electrode based passive pH sensors; inductive coil; integrated coupled-coil passive sensor; interrogator coil; pH combination electrode; pH measurement error; pH variation; quality factor; resonant frequency; sensor coil; temperature 25 degC to 60 degC; temperature compensated remote pH monitoring; temperature dependence; thermistor; varactor; voltage-dependent capacitance; wireless passive sensor; Coils; Electrodes; Resonant frequency; Temperature; Temperature measurement; Temperature sensors; Wireless communication;
Conference_Titel :
Sensors, 2011 IEEE
Conference_Location :
Limerick
Print_ISBN :
978-1-4244-9290-9
DOI :
10.1109/ICSENS.2011.6127181
