Water
and moisture sensing are becoming essential features measured
in clean energy and transportation applications. In this study, we
develop sensors with the ability to detect moisture through two distinct
conductive technologies: (1) a change in morphology using water-soluble
polymer composite foams and (2) a rust-induced change or resistance
change caused by the corrosion of a metal substrate. Five different
foam sensors were successfully fabricated, tested, and determined
as functional moisture sensors following their time and relative humidity
responses. The sensors’ sensitivity was calculated, and a maximum
sensitivity of 3.61 kΩ/RH % was achieved. The electrical properties,
foam morphologies, and chemical, thermal, and mechanical properties
of the foams were measured and compared. The second sensing technology
encompasses a magnesium–copper galvanic system which when in
contact with water for extended periods of time will corrode (i.e.,
convert the metal into metal oxide), causing an irreversible change
through an increase in resistance, subsequently alerting the user
of possible water flooding. The metallic sensors were tested at three
different outdoor temperatures (0, 23, and 50 °C) in order to
characterize the influence of temperature. They were also tested with
a direct force where corrosion was accelerated. Chipless microwave
resonators were utilized as platforms for investigation of the performance
of the developed sensors. Both technologies presented act as both
the substrate and sensing material.
This paper presents a third order continuous time current mode ΣΔ modulator for WLAN 802.11b standard applications. The proposed circuit utilized feedback architecture with scaled and optimized DAC coefficients. At circuit level, we propose a modified cascade current mirror integrator with reduced input impedance which results in more bandwidth and linearity and hence improves the dynamic range. Also, a very fast and precise novel dynamic latch based current comparator is introduced with low power consumption. This ultra fast comparator facilitates increasing the sampling rate toward GHz frequencies. The modulator exhibits dynamic range of more than 60 dB for 20 MHz signal bandwidth and OSR of 10 while consuming only 914 μW from 1.8 V power supply. The FoM of the modulator is calculated from two different methods, and excellent performance is achieved for proposed modulator.
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