TITLE:
Wide Range RH Detection with Digital Readout: Niche Superiority in Terms of Its Exceptional Performance and Inexpensive Technology
AUTHORS:
Manju Pandey, Kusum Sharma, Saikh Safiul Islam
KEYWORDS:
Ceramics, Sol-Gel, Nanoporous, Sensor, Toxic Gases
JOURNAL NAME:
Advances in Materials Physics and Chemistry,
Vol.9 No.2,
March
12,
2019
ABSTRACT:
In this paper we report alumina
based capacitive humidity sensor having exceptional sensing performance in wide
range RH segment (10% - 90%). The developed sensor has an improvement of
accuracy, reliability, and economic efficiency; apart from fast response and
recovery time (~s), negligible baseline drift and high selectivity
for moisture. The sensing mechanism was discussed based on their
microstructures, such as surface area and mesopore volume. In general, at low
humidity, surface area and water adsorption play the dominant role, while at
high humidity, mesopore volume and capillary condensation become important.
Standard characterization techniques such as AFM, FESEM, BET, XRD and impedance
spectroscopy were employed for micro-structural and electrical characterization
of RH sensor. The nano porous alumina film undergoes a huge change in
dielectric upon adsorption of moisture, ensuing large change in capacitance.
Additionally, a prototype RH meter has been developed with digital readout for
humidity. The interface circuit was based on capacitor-to-duty cycle (CDC)
converter. The proposed digital circuit has the advantage of performing
adaptive measurements as a function of resolution and bandwidth. The prototype
instrument can be used for sub ppm level moisture
detection where stability and response are completely unaffected even in highly toxic ambience viz. 4% ammonia and
4% chlorine.