Instruments for measuring indoor air humidity: types + selection recommendations

Alexey Dedyulin
Checked by a specialist: Alexey Dedyulin
Author: Anton Bondar
Last update: May 2019

A comfortable stay in the apartment is possible after providing a comfortable microclimate suitable for living quarters. The climatic conditions in the room depend on temperature and humidity, so these indicators must be carefully monitored with the help of special devices.

So, to determine the temperature in a room, a thermometer is used, and a device for measuring air humidity is called a hygrometer. The principle of the thermometer is familiar to everyone, and not everyone knows how a moisture meter works, and how to choose the suitable option.

Let's deal with the existing types of these devices and the features of their work in this material. Also let's talk about the rules for choosing a suitable hygrometer.

How is humidity measured?

You can find out the amount of moisture using improvised means: a lighted candle, fir cone, a glass of water or the condition of the leaves of a home-loving plant. Such methods have been used for a long time, but they determine only approximate values.

Accurate readings can be displayed with a conventional thermometer. This method is long and not very convenient, since it requires following certain instructions, without which the data obtained have a significant error.

Modern air humidity meter
Modern moisture meters are safe and harmoniously fit into the interior. Therefore, they can be used in any room to create a comfortable microclimate

For objective measurement of water vapor in the air, special instruments are used that convert data on temperature and vapor concentration.

Such devices include:

  1. Hygrometers.
  2. Psychrometers

Devices with different operating principles show values ​​with different degrees of error. Some of the devices give accurate data on the moisture content in the air, while others make an error.

There are instruments that record absolute values, there are meters that reflect the relative value. Therefore, before choosing a hygrometer, it is necessary to study the principle of operation of the devices and take into account the conditions in which the device will be used.

The absolute value reflects the weight of water vapor in a cubic meter of air. The value is indicated in grams, kilograms per meter per cube. Such a value will not say anything to an ordinary person, therefore, the relative humidity is considered to be the unit of measurement.

Relative humidity Is the ratio of steam to air. The maximum possible amount of steam in the air is 100%, other values ​​are displayed relative to the maximum value.

Hygrometer with temperature sensor
To calculate the relative amount of moisture in the air, each device is equipped with a temperature sensor. Some devices broadcast additional temperature data, which is convenient, since you do not need to buy an additional thermometer

According to SNiP 2.04.05-91 relative humidity should remain between 30-60%. In climatically humid areas, with a vapor content of more than 75% in the open air, the values ​​will be slightly higher.

The principle of operation and types of devices

The operation of hygrometers is based on variations in the physical parameters of various materials. When the amount of vapor in the air changes, the properties change: density, weight, length and other working parameters of the substances. By registering changes in the physical characteristics of materials, we can draw conclusions about the amount of vapor in the air.

Hair and film moisture meters

The simplest mechanisms of devices, analyzing the physical properties of materials, allow you to accurately determine the amount of vapor in the air.

Hair device consists of synthetic fat-free hair, a base with a scale, an arrow and a pulley. With increasing or decreasing vapor, the tension of the hair changes, the pulley rotates, changing the position of the arrow on the scale with the values.

Hair moisture meter
Rare and exclusive models of hair hygrometers operate exclusively according to the laws of mechanics, therefore, do not require an external power source

Such a meter operates in the range from 30 to 80%. Now it is practically not used, since there are other models that have a larger range of work.

AT film moisture meter an organic film attached to the pulley acts as a sensitive element. When the humidity indicator changes, the film tension increases or decreases, which leads to the movement of a pulley, which changes the angle of the arrow.

The pointer moves along the arcuate dial, showing the percentage of humidity in the room.

Both mechanisms operate according to the laws of mechanics; therefore, they can accurately measure moisture in rooms where the temperature is low, up to 0 ° С.

Weight and condensation meters

Via weight hygrometer can determine the absolute humidity. Such a device is used for laboratory experiments, so it is not suitable for home use in rooms.

Condensation meter summarizes the most accurate data. The design of such a device consists of a flat surface on which moisture settles, a thermometer that determines the moment of formation of condensate and a beam of light that captures the appearance of the first condensate. The operating range of the meter is from 0 to 100%.

Condensing moisture meter in the air
The condensing device is large. To bring the device into action, a rubber bulb is used, therefore, such moisture meters are used only in laboratories

These mechanisms generate results with high accuracy, which is necessary for research, but not as home air humidity meters.

Mechanical and electrical appliances

Mechanical or a ceramic moisture meter works by means of electrical resistance of the mass.Since the composition of the ceramic mass contains silicon and kaolin with metal particles, the resulting mixture changes resistance after changing air humidity.

Due to this, at different steam contents, the arrow on the device changes position, reflecting air humidity.

This mechanism of work allows you to make ceramic devices compact, so they are in demand for measuring air humidity in the home.

Electronic or room hygrometer - a modern high-speed device for determining the humidity of the air in the room.

The following principles of action can be used in the design:

  • conductivity measurement of ambient air;
  • optoelectronic method, with dew point measurement;
  • measurement of electrical resistance of polymers and salts;
  • condensate capacity analysis.

The digital moisture meter works with the help of microcircuits, therefore, the calculations are made within a few seconds, and the output data has a minimum error.

Digital Room Hygrometer
Accurate readings of an electronic hygrometer are possible in the absence of draft. Some models allow fluctuations of up to 2 m / s, in order to take this into account, you must first familiarize yourself with the technical documentation

When determining air humidity with devices of this type, the ambient temperature must be taken into account. The slightest deviations from stationary conditions affect the final indicators, therefore, before direct measurement, the street doors must be closed for 15 minutes.

In addition to temperature fluctuations, the proximity of heating devices affects the operation of devices. Therefore, when placing hygrometers of any type, consider the proximity of radiators and place them on the opposite wall or table, located at a considerable distance from the heaters.

The principle of the psychometer

Another device for measuring indoor air humidity is psychometer. The mechanism of operation of psychrometric devices is based on the use of physicochemical properties of liquids.

For measurement, two degree tubes with liquid are installed on the device, one of which is wrapped with a wet cloth. With moisture evaporation, the temperature indicator on a wrapped tube is lower than on a dry one.

Stationary psychrometer in a box
Mercury and toluene are used as liquid materials for filling psychometer thermometers. A device with toluene is less dangerous for domestic use.

To get the result, you need to look at the air temperature on a thermometer that is not wrapped in a cloth, calculate the difference in the liquid indicators between the two tubes.

Next, in the first column of the table of values, find the air temperature according to the thermometer. In the top line find the difference in values. The figure at the intersection of the column and row is an indicator of humidity.

Psychrometers come in three forms:

  1. Stationary. A simple device consisting of two thermometers enclosed in a meteorological flask. One of the thermometers interacts with wet tissue, and therefore, the liquid changes its physicochemical properties and a difference in degrees appears. The results are calculated according to the table.
  2. Aspirated the psychrometer is similar to a stationary one, the difference is that the protective case has an aspirator fan to move the compressed gas. A kind of vacuum creates the conditions for obtaining the most accurate indicators.
  3. Remote the device may be gauge or electric. The design contains pressure gauges or thermistors that change the resistance depending on the state of the environment. Finished results are displayed on the digital display of the device.

Psychrometric devices undergo standardization and verification, so the output values ​​can be considered the most accurate.

Stylish mechanical hygrometer
Stationary instruments for measuring the amount of moisture in the air are mounted and desktop, therefore, harmoniously fit into any interior

What to look at when buying?

Room models of instruments for measuring the amount of moisture in the air include mechanical and electronic hygrometers. They have a compact design, are safe for others and give a minimum error in the calculations. To maintain design ideas, modern devices have a sleek design.

Criterion # 1 - principle of operation

Mechanical and digital hygrometers have several advantages that can affect the choice of device.

The advantages of mechanical models of moisture meters include the fact that:

  • the device does not depend on external power sources;
  • they are easy to use, since minimal additional adjustment of the necessary operating parameters is required;
  • the cost of a mechanical hygrometer is slightly lower than electronic.

Digital models are made in the form of folding, portable gadgets.

In addition, the advantages of electronic models include:

  • high speed of result output;
  • smaller error of indications, in comparison with the mechanical device;
  • the output is subject to further processing, due to the presence of built-in internal memory.

Some electronic moisture meters combine several instruments at once: a hygrometer, clock, calendar, thermometer, barometer, dew point meter. Therefore, if the device performs several climatic functions - this stationary weather station.

Hygrometer with warning system
Some moisture meters have a built-in warning system, which is triggered when the steam level decreases or rises to the level of 30 and 60%. Such a device should be in homes where the climatic conditions of the region suggest increased humidity or dry air.

For the comfort of the child and parents, a hygrometer can be integrated into the baby monitor. Such a device has great functionality and a warning system.

The latest models are equipped with a Wi-Fi module to display weather information in the region by receiving data via the Internet.

Modern models of hygrometers are designed for a specific operation, therefore, in order to accurately measure air humidity in a room, apartment or other premises, it is necessary to understand how the device will be used. Then the purchased moisture meter will fully comply with the necessary requirements.

Criterion # 2 - humidity range

The optimum humidity is determined by the purpose of the premises. In the bedrooms, living room, the normal values ​​of the moisture meter are from 20 to 80%. Near the balcony, in the hall, attic and in the kitchen from 10 to 90%. Read more about the norms of humidity in the apartment, we recommend reading in this stuff.

In moisture-filled rooms, the range of operating values ​​can reach 100%. The wider the range of values ​​captured by the device, the higher the price for it. Therefore, when choosing a gadget for bedrooms, a hall and an attic space, you can stop the choice on devices with a small range of values.

Hydrometer for bath and sauna
When buying a hygrometer, study the performance characteristics indicated in the product passport. It is important that the instrument parameters include the upper range of the expected operating temperature

For some moisture meters, the maximum heating threshold is important. So, a device for a bath or sauna should include values ​​up to 120 ° C in the range of operating temperatures. Therefore, in rooms where temperature and humidity can reach rather high values, special instruments should be purchased for measuring vapor in the air.

Criterion # 3 - measurement accuracy

For the equipment of special storages, devices with the smallest error of indications are required.

So, in a home winery, the humidity of the circulated air should be kept at 65-75%, and the content of water vapor in the library should not be lower than 50 and above 60%.

Therefore, to measure moisture in the air in such rooms, you should use a psychrometer or high-precision electronic hygrometer, which measures the amount of water vapor by changing the electrical conductivity of the air.

Accurate digital hydrometer NTS-2
The error of the psychrometer ranges from 1 to 5%, the error of the digital device from 5 to 10%. Therefore, they can be used in rooms where air humidity must adhere to precisely specified values.

If the humidity level does not meet the standards, but you need a device to increase it - humidifier.

Conclusions and useful video on the topic

In the video, we will talk about the principles of stationary psychrometers, a comparison of the results with digital hygrometers will be given:

Optimum humidity in the rooms reduces the risk of chronic diseases, alleviates the symptoms of the course of existing bronchopulmonary diseases, and reduces the manifestation of allergic reactions.

The amount of moisture in the air affects the performance, appearance and health of a person. Therefore, measuring water vapor indoors should be a good habit in every family..

Still have questions about choosing a hygrometer? Or do you want to supplement our publication with useful comments? Write your comments under this material.

If you have a hygrometer at home and want to talk about its pros and cons, write about it below under the article.

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Visitors Comments
  1. Irina

    I had to buy a moisture meter because the device built into the humidifier showed incorrect numbers. Our air is very dry, so with a humidifier the difference immediately became noticeable. And it became easier to breathe, and now we are ill less. It would seem that such a trifle as air humidity, but makes life much more comfortable. We bought an electronic device, yet it is much more convenient.

  2. I bought an electronic hygrometer that shows both air temperature and humidity. Initially read reviews to be accurate. It's cold in our apartment. The temperature in the winter is 18 degrees, when it is cold, then it happens 16. I myself checked this parameter on an ordinary thermometer. And here, about humidity there was an ignorance, but the hygrometer showed the norm. Most likely, this is due to the coolness in the apartment.

  3. Denis

    I was presented with an electronic thermometer / hygrometer from Xiaomi, but I'm not sure that it shows the correct humidity. Are there any ways to check?

    • Expert
      Alexey Dedyulin

      Hello. In general, they check on special instruments, as well as by placing them on the street, after checking the humidity at the local weather service.

      3 interesting methods of experience are also used:

      1. Testing in a humid environment. When the appliance is wrapped in a damp cloth and placed in a closed plastic bag. After an hour, the humidity will be 96%. But it will be necessary to calibrate the device for this value in 1 minute, otherwise it will adjust to the room.

      2. Salt - in an airtight container (suitable for food), there is a container with wet table salt. A hygrometer is installed next to the tank, after 8 hours it needs to be calibrated by 75%.

      3. Using a reference hygrometer. If friends already have a calibrated device.

  4. So they would write which company has a hygrometer for determining humidity parameters in a room where there are little children. After all, there is no time to search, study these devices, compare characteristics.