hygrometer, also called hygrograph, is a laboratory instrument used to measure the humidity of air or another gas. That is, the hygrometer is a device whose function is to determine the humidity present in the environment.

Remember that air humidity refers to the percentage of water vapor present in the air. To measure air humidity using a hygrometer there are several methods, which is why there are different types of hygrometers. Each hygrometer variation is explained in detail below.

thermometer hygrometer

thermometer hygrometer is a measuring instrument that indicates the humidity and temperature of the environment. Therefore, as its name indicates, a thermometer-hygrometer acts as a thermometer and hygrometer at the same time, since it provides the temperature and humidity of the air.

So the difference between a simple hygrometer and a hygrometer thermometer is that the former is only used to know the humidity of the air, and the hygrometer thermometer is used to know the humidity and also the temperature of the air.

Currently, most hygrometers are digital and are used to measure both humidity and ambient temperature, so they should be considered hygrometers as thermometers.

What is a hygrometer for?

Mainly, a hygrometer is used to measure the humidity of the air in a room or hall. A hygrometer is useful to know the humidity in the environment.

However, when determining air humidity, the hygrometer can be used for different purposes:

  • To find out if bad weather is coming. In meteorology, hygrometers are used to know the humidity of the atmosphere and that information helps make predictions about when it will rain.
  • To assist in the preservation of very specific products. Since there are products that are very sensitive to changes in humidity, such as paper.
  • To know the level of air quality in certain premises. For example, in saunas or museums, hygrometers are used to check that the humidity level is adequate.


How does a hygrometer work?

In general, the operation of a hygrometer is based on absorbent substances, that is, substances that are capable of absorbing humidity from the air and then they lengthen.

Therefore, depending on the ambient humidity, the elongation of the absorbent substance is greater or less, and in this way the humidity of the air can be determined.

This means that for a hygrometer to work correctly, it must previously be calibrated to the type of absorbent substance used, because logically the elongation or reduction of the substance according to the variation in humidity will depend on the characteristics of said substance.

Once the hygrometer is calibrated, it should simply be left in the room or space where you want to determine the humidity, and after a while (normally a few minutes) the hygrometer will indicate in an analog or digital way the humidity value of the room. atmosphere.

Types of hygrometers

Hygrometers can be classified into two large groups: analog hygrometers and digital hygrometers. In analog hygrometers the measurement must be read, while digital hygrometers directly provide the measured value of humidity.

But hygrometers can also be grouped according to how they measure ambient humidity:

  • Hair hygrometer: consists of a group of hair that curls more or less depending on the humidity of the air. So the hair indicates the proportion of greater or lesser humidity, but they do not say its exact value.
  • Absorption hygrometer: it is made up of a chemical substance capable of exhaling or absorbing environmental humidity.
  • Electric hygrometer: it is composed of two electrodes wound in a spiral and impregnated with lithium chloride. After going through a chemical process, the hygrometer can accurately determine the humidity of the air.
  • Condensation hygrometer: Also known as a dew point hygrometer, this type of hygrometer calculates air humidity based on the concept of dew point temperature.
  • Digital hygrometers: taking advantage of the fact that the electrical resistance of some materials varies depending on the humidity of the air, this type of hygrometers establishes the environmental humidity through electrical circuits and shows the result of the calculation on a screen.

It should be noted that when the technology was not yet so developed, some types of hygrometers that are now falling into disuse were used more, such as the hair hygrometers.

And a very similar ancient variation of the hygrometers that is still used today is the psychrometer, which calculates the relative humidity of the air with two thermometers, one that is dry and one that remains humid.

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