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Humidity sensor

dariush

Jun 26, 2013
6
Joined
Jun 26, 2013
Messages
6
whats the difference of Capacitive and resistive humidity sensor?
which one is your choice if you want to make a humidity sensing board? and why?
tell me which one is better for me through rational reason. in a paper i read an ideal sensor should have these factor:
linear response
from 0% to 100% RH, short response time, high
selectivity (i.e., low or no cross-sensitivity), and
high long-term stability
what does these mean and when are they important?. tell me which one is more suitable resistive or capacitive ?
 

Abhimanyu

Sep 17, 2016
2
Joined
Sep 17, 2016
Messages
2
Capacitive relative humidity sensor are consist of a substrate on which a thin film of polymer or metal oxide is deposited between two conductive electrodes. The sensing surface is coated with a porous metal electrode to protect it from contamination and exposure to condensation. The substrate is typically glass, ceramic, or silicon. The incremental change in the dielectric constant of a capacitive humidity sensor is nearly directly proportional to the relative humidity of the surrounding environment. The change in capacitance is typically 0.2–0.5 pF for a 1% RH change, while the bulk capacitance is between 100 and 500 pF at 50% RH at 25°C. Capacitive sensors are characterized by low temperature coefficient, ability to function at high temperatures (up to 200°C), full recovery from condensation, and reasonable resistance to chemical vapours.

Resistive humidity sensor measure the change in electrical impedance of a hygroscopic medium such as a conductive polymer, salt, or treated substrate. The impedance change is typically an inverse exponential relationship to humidity
 
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