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Humidity sensor

Discussion in 'Sensors and Actuators' started by dariush, Jul 8, 2013.

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  1. dariush

    dariush

    6
    0
    Jun 26, 2013
    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 ?
     
  2. Abhimanyu

    Abhimanyu

    2
    0
    Sep 17, 2016
    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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