Tuesday, February 19, 2013

Humidity Sensors


       A humidity sensor measures three different types of humidity; absolute humidity, relative humidity, and specify humidity. Absolute humidity is the ratio of water to air, the total mass of water vapor that is in the air at a given time. Relative humidity (RH) is where many believe is temperature is actually the saturation level of the air. It’s shown as a percentage of the ratio of the moisture in the air and the total amount of moisture the air can hold. If the RH is at 100% then the air cannot hold any more moisture which can mean a high possibility for rain. The warmer the air is, the more moisture it can hold, the colder the air the less moisture. Meaning that the RH is affected by the change in temperature, which can justify why some believe humidity sensors measures temperature. Specific humidity is the ratio of the mass of water vapor in the air to the total mass of the mixture of air and water vapor. These humidity sensors can be used both indoors and outdoors, as well as being available in both digital and analog forms. The analog sensor uses a system called capacitive measurement. The sensor would be made of either glass or ceramics. The insulator material made from polymers, absorbs and releases that water which changes the level of charge in the capacitor. The measure of the change in the charge is the humidity of the given area. The digital sensor uses an electrode based system consisting of polymers, there are two micro sensors that are calibrated to the humidity of the given area. Which are then converted into digital format using an analog to digital conversion. There are actually another type of system called the hygrometer, where there is a pair of thermometers are used. One is kept wet while the other one is kept dry. The difference of the two moisture levels are measured. I really liked how in Nastasha’s blog, she when more in-depth with the components and circuitry of the sensors. There are many applications that a humidity sensor has. To regulate humidity in buildings like museums, laboratories, and wine cellars. Create a sterilized environment for a hospital and even the defogging or defrosting systems in cars need humidity sensors. Humidity sensors are key into making a green building as in Jeanine’s blog, she mentioned that “The humidity sensors will collect data that will be used to determine the comparative advantages and worth the new technology.”

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