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What are Hygrometers?

11/18/2013 8:12:35 AM | by Anonymous


Hygrometers are instruments used for the measurement of the relative humidity of air. On top of that, it also measures the amount of invisible water vapour that is in the given environment. They typically range from simple devices such as hair hygrometers to psychrometers as well as other types of more complicated pieces such as the cooled mirror dew point hygrometer that utilizes the temperature of condensation in order to measure the humidity. Similarly, the modern electronic equipment can also be used to determine the humidity just by detecting the change in the electrical applications.


Apart form being used in greenhouses and industrial spaces, the hygrometers are also commonly used in incubators, humidors, saunas and museums. They are also typically under the care of wooden musical instruments. Some of which are violins and guitars that can be damaged due to the improper humidity conditions. Additionally, in residential settings, hygrometers can help to aid the humidity control. This is due to the fact that if the humidity is too low, it poses various potential damages to the human skin and human body. However, if it is too high, the humidity will favour the growth of dust mites and mildews.


The coating industry also uses hygrometers. The application of paint as well as the other types of coatings can also be very sensitive to the dew point as well as the humidity. With the growing demand on the amount of measurements taken with the psychrometer, it is now replaced with the dew point gauge known as the dew check. These devices help to ensure that the taking of measurements is done a lot faster than usual. They are also generally more efficient. However, one downside is that they are not allowed in explosive environments to prevent any possible or unforeseen explosions from occurring.


The psychrometer consists of two thermometers within itself. One of it comes with a bulb that is relatively dry whereas the other is wet. They use the evaporative cooling for the measurement of humidity. Whenever the moisture evaporates form the wet bulb, the temperature will drop and the relative humidity is then computed. It is computed using the difference in temperatures between the wet and dry bulb thermometers measured against the psychometric chart.


One of the simplest forms of a hygrometer is the sling psychrometer. It uses the wet and dry bulb method with thermometers that are mounted in the air on either a rope swing or a chain. The condensation is typically known as the cooled mirror dew point hygrometer. It is one of the more precise instruments available. The feedback control is electronic and it controls the temperature of the chilled mirror exposed to the open air. This would help to keep the dynamic equilibrium between the condensation and evaporation on the mirror.


The optoelectronic mechanism can also detect the condensation on the mirror surface followed by measuring the dew point temperature. Additionally, it also measures the point at which the air becomes saturated. At this point, it can no longer hold the water vapour followed by the condensation occurring.


The hair hygrometer utilizes hairs that are under tension to measure the humidity of the area. Hair becomes longer before it drops when the relative humidity increases. This would result in the hair to become shorter. The instrument then uses the strands of hair that is attached to different levels that magnifies the changes in length. The hygrograph would consist of a rotating cylinder and ink pen to record the variations of humidity through out the hours of an entire day. However, it is important to know that hair hygrometers are generally not as accurate as other components. They register the errors that are significant at high and low extremes of the relative humidity.

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