Optimizing the Materials Response in Humidity Capacitive Sensors

Authors Elham Noroozi Afshar1, Hossein Golnabi2, Nima E. Gorji3

1 Department of Physics, I. Azad University of Tehran, Northern Tehran, 16679 Tehran, Iran

2 Department of Physics, Sharif University of Technology, 11155 Tehran, Iran

3 Department of Electrical Engineering, University of Bologna, 40136 Bologna, Italy

Е-mail nima.s.gorji@gmail.com
Issue Volume 7, Year 2015, Number 3
Dates Received 16 July 2015; revised manuscript received 15 October 2015; published online 20 October 2015
Citation Elham Noroozi Afshar, Hossein Golnabi, Nima E. Gorji, J. Nano- Electron. Phys. 7 No 3, 03045 (2015)
PACS Number(s) 07.07.Df, 84.37. + q
Keywords Humidity sensor, Capacitance (8) , Output (4) , Dielectric constant (8) .
Annotation The number of humidity outputs on the cap of a cylindrical capacitance sensor is optimized by designing three different probes with direct and indirect windows. The time interval is measured within which 30-70 % humidity can influence the dielectric constant and conductivity of the capacitance when exposed to a range of relative humidity. It is then compared with a simple set-up including a simplified equivalent circuit. The direct probes had four and double outputs on the window of the cylindrical capacitive sensor while the indirect probe had a thin plastic layer only. We observed that the dielectric constant and its conductivity depend closely to the humidity outgoing pathway and also to the increasing rate of humidity between the capacitance plates. The final variation in the materials properties alters the capacitance of the sensor which is measured simply by a LCR. This technique presents a simple method for tracking the recovery and reliability of the humidity sensors over time and assists in optimizing and controlling the materials response to the relative environment humidity. As a result, by controlling the environment humidity rate (0.02 %/s.), we could measure the increment rate of capacitance with accuracy of 0.01 pf/%.

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