Twin-T Oscillator Containing Polymer Coated Parallel Plate Capacitor for Sea Water Salinity Sensing

Shreyas Bhatt, Abdur Rub Abdur Rahman, Sunil K. Arya, Shekhar Bhansali

Bioelectronics Program, Institute of Microelectronics, A*Star, Singapore Science Park II, Singapore City, Singapore.
BioMEMS and Microsystems Lab, Department of Electrical Engineering, University of South Florida, Tampa, USA.
Department of Electrical and Computer Engineering, Florida International University, Miami, FL, USA.

DOI: 10.4236/ojab.2013.22007                

Abstract

This paper presents the development of a Twin-T oscillator comprising polymer coated parallel plates as a sensor for ocean water salinity monitoring.This sensor employs a parallel plate capacitor design, with sea water serving as the medium between plates. Novalac resin and a proprietary commercial polymer (Accuflo^TW) were investigated as corrosion protective coatings for the copper electrodes of the capacitor. Electrochemical Impedance Spectroscopy (EIS) was employed to evaluate corrosion inhibition of polymer coatingin sea water. A detection circuit was designed and simulated using P-spice and then implemented in Printed Circuit Board (PCB). EIS results indicate that Accuflo exhibits better corrosion inhibition in ocean water than Novolac. Further, the use of Twin-T oscillator based detection circuit resulted in enhanced sensitivity and better detection limit. Experiments performed using ocean water samples resulted in oscillator frequency shift of 410 Hertz/power supply unit (Hz/PSU). Oscillator frequency drift was reduced using frequency-to-voltage converters and sensitivity of 10 mV/PSU was achieved.

Keywords

Impedance Spectroscopy; Salinity Sensing; Capacitive Sensors; Polymer Coating; Twin-T Oscillator

Conflicts of Interest

The authors declare no conflicts of interest.

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