PSYCHROMETER: WHAT IS IT FOR, HOW DOES IT WORK, TYPES - TECHNOLOGY - 2024

The psychrometer is an object that is used in the area of ​​meteorology in order to calculate the amount of vapor that exists in the air. It is a value that must be established in order to more accurately calculate the level of relative humidity present in the environment.

It is an instrument widely used to study the state of the weather, since its predictions allow us to analyze and explain certain phenomena or states that occur in the atmosphere.

Source: Fudeba at Portuguese Wikipedia, via Wikimedia Commons.

The word psychrometer is born from the union of two Greek terms that refer to the words 'cold' and 'measure'. The use of the termination 'meter' to give names to scientific devices is very common as seen with other instruments such as: stopwatch, barometer, tape measure and odometer, just to name a few.

The process of measuring a psychrometer varies depending on the type, but in general it is the comparison that is made between the values ​​of two thermometers, one of them wet and one of them dry.

What is a psychrometer for?

Meteorology is a science that is closely linked to other scientific disciplines such as chemistry or physics. That is why the measurement of different values ​​is done, fundamentally to know different aspects of atmospheric phenomena.

In the case of the psychrometer, its objective is to measure two different temperatures that, together with the analysis of predefined schemes, will allow to know the value of the water vapor in the air.

For this, the presence of a thermometer that calculates the degrees of the ambient air and another thermometer that works with a wet bulb is relevant. In addition, it is important to emphasize the need to have psychrometric charts, although today everything is much more automatic thanks to technology and the use of computers.

How does it work?

The psychrometers are composed of two thermometers with the same characteristics as the traditional ones, made of glass and with a mercury line. Each thermometer has a different function and they differ in their name: wet and dry bulb.

The methodology for using a psychrometer consists of analyzing the readings of both thermometers. The first step is to use the dry bulb to calculate the degrees present in the area.

Then, the cloth that covers the wet bulb should be impregnated with water as much as possible. The objective is to produce a drop of liquid at the bottom of the instrument.

The most recommended is to wet the cloth with the help of a container that allows the cloth to be submerged. You also have to try to keep the water clean to avoid any kind of alteration in the measurements.

Precautions

When using a psychrometer you have to take into account different details that could affect the temperature reading.

Whoever handles the instrument must keep a safe distance so as not to transmit heat to the thermometers. Avoid lamps especially when it is night or stay in a shady place if the study is carried out outdoors.

Maintenance

All details are relevant in scientific studies. Therefore, it is necessary to pay attention to the condition of the instruments to protect both the measuring devices and the values ​​to be obtained.

The water used to soak the wet bulb cloth should be changed after each measurement that is made. The cleaning of the container where the water is also must be taken care of. As a general rule, it is recommended to change the cloth that covers the thermometer every week.

Types of psychrometers

There are different psychrometers that can be used, although they all fulfill the same objective of calculating the humidity present thanks to the contrast of values ​​between two thermometers.

They can be classified according to different factors: the accuracy of the data they present or the environmental conditions of the site where the psychrometers are to be used.

In addition, these instruments have evolved over the years and the presence of digital readings is now common, simplifying the investigation and making the process faster.

There are the wall psychrometers, the rotary ones, the Assman ones, the meteorological ones or the digital ones. They are also usually classified by psychrometers of natural ventilation or those of artificial ventilation.

The simplest instruments are usually wall psychrometers, very common in homes. Although, as is evident, they are not the most accurate in terms of their temperature measurements because normally they are not in controlled environments.

The rotary psychrometer is an advance over the wall psychrometer due to its use. It is portable and, as its name suggests, it rotates so that the generated wind allows the data to be obtained. Its use is very common for field studies, as is the case with Assmann's psychrometer.

The meteorological ones are present in stations and are operated by official organisms that are in charge of this area of ​​science. The measurement range they have is much wider. The normal thing is that they use digital psychrometers that no longer have traditional mercury thermometers.

When taking into account present ventilation, natural or artificial, psychrometers vary because the former tend to be less precise in their measurements.

History

One of the first references to the use of the word psychrometer occurred in the 18th century. At that time the device was defined as the one in charge of calculating the point at which it cools in air and it was compared with the thermometer.

In the middle of the following century, in the Encyclopedia Britannica, the thermal psychrometer already took the same definition that it has today: an instrument made up of two thermometers.

Hygrometer vs psychrometer

Many scientists have established that a psychrometer is simply a variation of hygrometers. The difference is that psychrometers analyze humidity thanks to the comparison and analysis of two temperatures that were achieved thanks to different methods.

In the case of psychrometers, it is normal that the use of other tools is needed, such as tables or lists with data that allow calculations to be made to arrive at the value of the humidity present in the environment.

References

1. Allen, S., Brenner, A. and Grace, J. (1994). A low-cost psychrometer for field measurements of atmospheric humidity.
2. Belloc, H. (1967). On. Freeport, NY: Books for Libraries Press.
3. Electric fan psychrometer. (1958). Washington, DC: US ​​Dept. of Agriculture, Forest Service.
4. Kohsiek, W. and Monna, W. (1980). A fast response psychrometer. From Bilt: KNMI.
5. Taylor, D. (1963). Mortarboard psychrometer. Asheville, NC: US ​​Dept. of Agriculture, Forest Service, Southeastern Forest Experiment Station.