There are many things required to condition indoor air quality to human comfort. Especially cold winter like this term, it is easy to experience what low humidity can do to human comfort. However, too high of humidity can also create discomfort for indoor environment. That's when the humidity sensor takes a role.
Humidity is not only effecting human comfort, but many others that could be affected like followings;
(1) Many industrial processes are humidity sensitive;
product quality, yield, and cost often depend on controlling the humidity
within some acceptable band.
(2) Human health, comfort, and productivity are adversely
affected by extreme relative humidity.
(3) Optimal functioning of various home appliances
necessitates humidity sensing and control.
(4) Modern, solid-state electronic equipment is susceptible
to damage by the discharge of electrostatic energy that can accumulate if the
environment is too dry.
- Kulwicki, 1991
Among many different sensors out there, there are two main sensors being used the most: ceramic and polymeric humidity sensor. Ceramic sensor is based on the absorption of water molecules through porous semi-conductor. Polymeric sensors can be divided into two categories: one using capacity of sensing principle, while the other uses resistant effects. Capacitive effect is basically sandwich the hygroscopic dielectric material with a pair of electrode forming a small capacitor. This capacitor will determine the values based on presences of moisture. Resistive effect is based on number of movable ions sensed by polymeric film. Change in humidity will change in resistance of the film.
Despite the fascinating process of sensors, they are not always accurate. For ceramic sensors, it requires integral heater to calibrate the system. The system often be contaminated by oil vapors or smoke. The cost of the sensor would go proportion with frequent of self heating process and the complexity. On the other hand, polymeric humidity senors are bulk effective sensors that it's less sensitive, slower respond time required, and hysteresis, but it has lesser chance to get contaminated like porous ceramics.
Different sensors will be used in different environment and preferences. It goes same to BIM as well. BIM model will analyze the building before it was built. It will analyze the indoor air quality to make sure it is in good shape for people to living in. However, BIM model does not consider long term effects like how oil vapors and smoke affect on humidity sensors, at least, revit doesn't. BIM can be very useful in many different way, but putting all the trust in BIM could cost owner more money than without BIM. BIM is relatively new to the industry. There are many tasks that could be done in BIM, but many many people, especially owners, expect more than what it can do. All the owners and BIM users should study and understand the process of construction and maintenance while understanding the program itself.
Sources:
http://www.engineersgarage.com/articles/humidity-sensor
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