| Science and processing technology rely on humidity | | | | greater robustness. |
| sensors as part of control systems in a variety of | | | | Dew point is the combination of temperature and gas |
| applications. Many people are aware of the relative | | | | pressure at which water vapor begins to condense |
| humidity number reported by the local weather | | | | into liquid. Most people understand this in weather |
| reporter on TV. While this helps the average citizen | | | | report terms but it is an important factor in many |
| prepare for his day, it is only one very small reason | | | | scientific calculations and processes outside of |
| for the existence of sensors to measure humidity. | | | | weather. Early dew point measurements used chilled |
| Humidity has impacts on a wide range of industrial | | | | mirror technology which was both expensive and |
| and scientific processes and makes a difference in | | | | temperature limited. Modern electronic dew point |
| everyone's daily lives. This short article will examine | | | | sensors are accurate down to -40degrees F. |
| the technology and uses of humidity measurement. | | | | Absolute humidity is the precise measurement or |
| The basic definition of humidity is the water vapor | | | | calculation of the mass of water vapor in a given |
| content in a gas such as air or nitrogen. Notice this | | | | volume of air or other gas. (Expressed as grams per |
| refers to water vapor - not water in any form. | | | | cubic meter or grains per cubic foot) This is the most |
| Water existing as a mist or ice crystal in air is not | | | | useful measurement for a variety of applications. One |
| within the definition of humidity. Also, humidity is | | | | interesting application is in drag racing. The grains [of |
| discussed in various terms depending on how the | | | | water in the ambient air] number is used by all race |
| measurement is made and used. Within certain ranges | | | | teams in setting up their racing engines. Modern |
| it is possible to calculate the equivalent measurement | | | | electronics can measure absolute humidity at |
| in different terms, such as converting relative | | | | temperatures greater than 200 degrees C in almost |
| humidity measurements to dew point temperatures. | | | | any environment. |
| Three often used measurement terms are relative | | | | Sometimes process stability problems are related to |
| humidity, dew point and absolute humidity. Each of | | | | humidity changes in the process environment. |
| these is measured differently and used differently in | | | | Monitoring humidity can provide clues why results are |
| process controls or data recording applications. | | | | not consistent. Painting quality can suffer when |
| Humidity measurement methods have evolved | | | | humidity changes and the process is not adjusted to |
| tremendously over the decades. | | | | compensate. The wide range of sensors on the |
| Early scientists realized human hair changed when | | | | market today assures coverage for any perceivable |
| water content in the surrounding air changed. This led | | | | application. |
| to mechanical devices that indicated humidity by the | | | | Humidity sensor manufacturers can deliver accuracy, |
| changes in a strand of hair. Both human hair and | | | | robustness, size, and cost to meet just about any |
| horse hair were used to power indicators or chart | | | | scientific or technological requirement. Some online |
| recorders. Materials technology provided nylon and | | | | research is sure to reveal a variety of options for |
| other synthetic fibers that were more predictable | | | | any application. This article should provide just enough |
| and easily calibrated. Today, relative humidity sensors | | | | information to make your research more effective. |
| are solid-state electronic devices with lower cost and | | | | |