How to use a hygrometer - What is a hygrometer, description of the device, photo, principle of operation. What are hygrometers for and what do they measure? Hygrometer: types, features, areas of application Hygrometer units of measurement

16.10.2017

Hygrometers are devices whose main function is to measure humidity. This indicator affects human health, the operation of many devices, and the properties of materials, so the need to control it may arise in various industries. During the use of the hygrometer, various principles actions that have become widespread.

Types of hygrometers

There are several methods for measuring humidity. Absolute humidity characterizes how much water vapor that is currently contained in the cubic meter atmosphere. Relative humidity is a characteristic that shows how close the amount of moisture contained in the air at the time of measurement is to the maximum possible for a given temperature. It is measured as a percentage and is often used to describe the weather conditions. Finally, in addition to absolute and relative humidity, a hygrometer can determine the dew point - the temperature at which water vapor contained in the air condenses on a cold surface.

As a rule, measuring equipment determines one of the three listed indicators. However, there are formulas that allow you to obtain the remaining two using calculations. Therefore, regardless of whether your hygrometer measures dew point, absolute or relative humidity- you can calculate all three characteristics if necessary.

During the existence of the hygrometer, several methods have been developed to determine air humidity. They differ in the accuracy of the data obtained and in the scope of application.

IN hair hygrometers The measurement is carried out by the fact that the length of the fine hair changes in response to the amount of moisture with which it comes into contact. The device has certain limitations - measurements are carried out only in the range from 30 to 80%. Humidity indication is carried out through a simple mechanism. Changes in microclimate affect the hair, the tension of which increases or decreases. It acts on the pulley to which it is connected. The pulley turns and moves the pointer along an arc-shaped scale. Since the operation of such a hygrometer is determined solely by the laws of mechanics, it does not require an external power source.

To determine absolute air humidity, use weight hygrometer. It consists of tubes bent in the shape of a U, connected to each other and filled with a substance with good hygroscopicity, that is, it actively absorbs moisture from the air. A fixed amount of air is blown through the described tube system. The moisture contained in it settles on the contents of the tubes, and their mass changes. The difference between the mass of the tube system before and after taking measurements allows you to calculate how much moisture is present in a given volume.

At the heart of the work mechanical (ceramic) hygrometer- change electrical resistance mass containing ceramic and metal components. The base is silicon, clay or kaolin, to which metal oxides are added. The result is a mixture that noticeably changes resistance in response to changes in humidity. Hygrometers of this type are often used in everyday life.

Allows you to obtain more accurate data than described above mechanical devices. The design of such a device includes a cooled surface on which moisture condenses. The built-in thermometer records the temperature at which condensation occurred, and a narrow beam of light directed at the mentioned surface allows you to accurately record the moment of condensation formation. Based on this data, the electronics calculates the relative humidity and displays it on the display. This principle of operation allows you to reduce the error to a minimum, performing measurements in the range from 0 to 100%.

IN electronic hygrometers Various operating principles may be used, including:

• measuring the electrical conductivity of air, which depends on the moisture it contains;
• determination of dew point by optoelectronic method;
• measuring the electrical resistance of salts or polymers, which changes depending on humidity;
• monitoring changes in the capacitance of a metal oxide or polymer capacitor.

All of these methods provide more accurate data than using a mechanical hygrometer. Electronic hygrometer gives less error and is especially convenient if further processing of the collected data is necessary.

Used to measure relative air humidity by comparing the readings of two thermometers, one of which is placed in a humid environment. Since the wet one will cool due to the evaporation of the liquid, it will show a lower temperature than the control one. Moreover, the less moisture in the air, the more the thermometer readings will differ. Relative humidity is determined using a special table, and on its basis, if necessary, absolute humidity is calculated.

Based on this principle, several types of psychrometers operate:

• Stationary represents simple design, mounted in a meteorological booth. Two thermometers are mounted on a tripod, one of which is in contact with a damp cloth. Readings and calculations are done manually.
• The remote is constructed using temperature transducers such as thermistors or thermocouples. For example, such a psychrometer may consist of two manometric thermometers, one of which is humidified. A remote psychrometer can be manometric or electrical.
• The aspiration thermometer consists of two thermometers mounted in a protected housing and blown by an aspirator fan. This design allows for the highest measurement accuracy.

Scope of application of hygrometers

Problems requiring humidity control often arise in various industries. Modern manufacturers produce hygrometers designed for specific specific applications, which means they the best way adapted for use in a particular field of activity. Here are just a few examples of situations that can be solved using these measuring instruments:

• For long-term storage of agricultural products, for example, in vegetable stores or granaries, it is necessary to maintain temperature and humidity conditions. This can be achieved by constantly monitoring the microclimate using a hygrometer.
• Many medications require special storage conditions and may lose their properties if they are exposed to excess humidity.
• A hygrometer is also necessary in a library, since books, especially old ones, deteriorate much faster in a humid microclimate. Materials that are many years old can deteriorate from excess moisture, which means that air humidity needs to be controlled to ensure optimal mode storage
• The need to control the moisture content of materials often arises at a construction site. For example, the degree of drying of wood is checked to determine whether and how it can be used as a building material. There are also specialized hygrometers designed to determine the moisture content of concrete.
• Checking the moisture content of materials is often carried out during the production of furniture, because a product made from too damp or overdried wood was produced in violation of the technology and, most likely, will last much less.

A hygrometer measures more than just humidity atmospheric air, but also the proportion of moisture in gaseous media. For this purpose, professional devices are used to analyze the temperature and humidity of non-aggressive gas environments. The measurement result is often expressed in dew point units. They can be portable or stationary.

Portable

The main areas of application for portable hygrometers are the oil and gas and petrochemical industries. Using such a device, the microhumidity of gas in cylinders or pipelines is determined. They can operate over a wide temperature range and output humidity in different units of measurement. The compactness of the hygrometer allows you to easily take measurements at the right points.

Video review of a portable electronic hygrometer

Stationary

Stationary hygrometers allow not only to take measurements, but also to control technological processes. The design of the device allows you to detect even a small percentage of microhumidity. The sensor heating system makes measurements more accurate by preventing the sensor from being exposed to drying agents that may be contained in gas mixture.

Scope of application of professional hygrometers

Portable and stationary humidity measuring instruments are used primarily in the oil and gas and chemical industries. However, the scope of their use is not limited to this. A hygrometer may be needed wherever you are supposed to work with non-aggressive gas mixtures and you need to monitor their condition. Thanks to this, equipment for measuring the percentage of moisture in the air is used at nuclear power plants, in the production of microelectronics, and in the energy sector. They are also used to control the drying process of natural gas.

Professional hygrometers are used to solve a wide range of problems related to the organization of various production processes. In particular, they become indispensable if necessary:

• provide a given level of humidity in the room, for example, for storing products under certain conditions;
• estimate the humidity in production premises for labor protection purposes;
• ensure the normal functioning of electrical equipment for various purposes;
• provide the level of humidity required for the implementation of a specific production process.

How to choose a hygrometer

To choose the right hygrometer, decide how you will use it. In everyday life, preference is given to inexpensive mechanical hygrometers, while in production, mainly electronic ones are used. various types, because they provide the highest measurement accuracy.

It is important to decide what the device will be used for primarily and how often measurements will be taken. For use in construction, you may need a specialized hygrometer to work with a certain group of materials, for example, wood, but in other cases a standard model will be suitable. Determine what you want to measure and evaluate the capabilities of the various hygrometers on the market.

The conditions of use are also a significant factor. Pay attention to the range of temperature and humidity in which the device will give correct readings. Depending on the specifics of the production, you may need a hygrometer that operates at extremely high or extremely high temperatures. low temperatures. The uncertainty of changes should also be taken into account.

It also matters how the received data will be processed in the future. In the simplest case, you just need to take one measurement to estimate the air humidity in the room or the microhumidity of the gas mixture. But stationary hygrometers allow you to solve more complex problems. With their help, you can monitor changes in parameters, signal when threshold values ​​are reached, and therefore control the technological process more effectively.

Don’t forget about the ergonomic characteristics of the device. Large numbers on the display should be contrasting and easy to read. You may prefer to purchase a backlit model so that you can easily read the readings in any light level. Ergonomics is especially important for portable devices: their body should be light, so that it is comfortable to hold in the hand.

A professional hygrometer is a tool that is widely used in various industries. It helps control air humidity, ensuring the safety of people and the stable operation of equipment.

I live near the sea, and the issue of climate in the apartment is very acute. Signs of corrosion have recently appeared on stainless steel surfaces. kitchen sink and coffee machines. In case of serious deviations in indicators such as temperature, humidity and Atmosphere pressure, health worsens. Neighbors install air conditioners in their apartments, but even if there is one, it can be important to find out the indicators. I was puzzled by the search for a universal device with various sensors and came across an interesting device that I want to talk about.

A hygrometer is a special measuring device, which determines with high accuracy the humidity of surrounding air masses. The range of devices includes desktop and wall-mounted modifications with mechanical and electronic principle work. Most of them are equipped with a thermometer to measure temperature. Despite its importance, the device is not widely used in residential premises and public institutions, but is used more often at weather stations and control services.

Experts recommend maintaining indoor humidity as strictly as temperature. This is due to several factors:

• A too humid environment causes colds to spread quickly, and fungi and mold to form on building structures.
• A dry atmosphere is also harmful to health. Dried mucous membranes in the throat and nasopharynx quickly lose their protective properties.
• When there is an excess of moisture in the pantry, vegetables begin to rot, and when there is a lack of moisture, they wither and become inedible.

Construction requires maintaining constant humidity, food industry and medicine, public utilities and greenhouses, enterprises, schools and preschool institutions. Knowing and controlling its indicator in a given range, you can improve all areas of your existence (including health and material well-being).

Types of devices

Having found out what a hygrometer is and what it is needed for, it is worth understanding what types of devices are available and where it is best to use them. Wide the lineup combines both simple mechanical and more complex electronic products. They can have both household and general purpose, and most of them are designed to be connected to an air conditioner or humidifier. Depending on the complexity, the devices show the amount of moisture content in air masses (the number of water vapor per m 3 of air) or the humidity ratio as a percentage. In the first case, the simplest models are used, and in the second, professional specialized equipment is used.

Mechanical hygrometers are good for measuring the percentage of moisture in your home (apartment). They are inexpensive, have a simple design, but react poorly to minor changes in humidity. The simplest of them do not pass verification meteorological services and certification. The values ​​they produce often only approximately coincide with the actual parameters environment. The devices are highly sensitive to mechanical stress and therefore need to be treated with the utmost care. They are picky about their location, and when placed on the wall they do not like subsequent movements. For them, stationary operating mode is preferable.

Electronic meters have more high price, but also certain advantages over mechanical prototypes. They cover a wide temperature Range(from -30 to +60 C), even record minor changes environments, visually provide data and can combine the functions of other equipment (barometer, thermometer, clock, etc.). Appliances used in everyday life are distinguished by their compactness, varied modern design and can be placed anywhere. The most “advanced” of them work with several sensors located in different rooms and even on the street. By processing the information received, the system itself maintains the specified regime in the house.

Also in the group of mechanical hygrometers there are hair, weight, ceramic, condensation and psychrometric devices. Let's look at them in more detail.

Mechanical hygrometers

The cheapest and simplest of them are hair hygrometers. They use regular hair or pine shavings to take readings. It is attached to the frame and to the arrow of the device. The hair changes length with changes in humidity, moving the arrow along the scale (the hair shavings can unwind or curl). You can't use the device precise measurements, but for home use it fits quite well.

Weighing hygrometers use several tubes with an active hygroscopic substance connected together. When a measured portion of air is drawn through the circuit, some of the moisture is absorbed from it. By using the mass of the tubing system “before” and “after” the drawn volume, as well as carrying out the necessary mathematical calculations, the required absolute value can be determined. To minimize errors in calculations, it is better to use the model in laboratories.

In ceramic hygrometers, the sensitive working element consists of a porous or solid ceramic mass of kaolin, silicon and clay with metal oxides. The change in its electrical resistance is directly dependent on humidity. For the device it is desirable room conditions and constant temperature, although even if such requirements are met, the accuracy of its readings remains low.

The operation of compensation models of devices uses the phenomenon of condensation on a cooled metal mirror. The lower the temperature required for its appearance, the drier the surrounding air. Measurements in them are carried out using semiconductor elements, which makes the designs the most accurate of those existing for domestic use.

Without knowing what psychrometric type hygrometers look like, they can easily be confused with ordinary thermometers. But they contain two temperature columns: dry and moist. The air humidity value is determined by the rate of evaporation of the moisturizing liquid and the difference in the readings of two thermometers. Psychrometers are not hygrometers in the literal sense, but are identified with them. The devices allow you to take readings with an average degree of accuracy, but require constant moistening.

Choosing a household hygrometer

For the right choice the required device, decide on its location and the options you need. Calculate options for installing additional radio-controlled equipment for it. Check out the technical specifications of the devices and their IP rating. When considering budget models with low measurement accuracy, choose the one that is less demanding to operate. If you want to measure more accurately, look for one with good functionality and a long-term warranty.

When purchasing, check what exactly the hygrometer measures. This can be either absolute humidity in g/m3 or relative humidity in RH. Try to measure the required indicator as accurately as possible on different models yourself. Find out what temperature range the device is designed for. Only then make a decision and carefully check the included instructions.

There are several types of hygrometers (weight, hair, film and others), the operation of which is based on different principles.

Types of hygrometers

1. Weight(absolute) hygrometer consists of a system of U-shaped tubes filled with a hygroscopic substance capable of absorbing moisture from the air. A certain amount of air is drawn through this system by a pump, the humidity of which is determined. Knowing the mass of the system before and after measurement, as well as the volume of air passed through, find absolute humidity.

2. Action hair The hygrometer is based on the property of defatted hair, which can change its length when air humidity changes, which makes it possible to measure relative humidity from 30 to 100%. The hair is pulled to metal frame. The change in hair length is transmitted to the arrow moving along the scale.

3. Film The hygrometer has a sensitive element made of an organic film, which expands when humidity increases and contracts when humidity decreases. The change in the position of the center of the film membrane is transmitted to the arrow. Hair and film hygrometer in winter time are the main instruments for measuring air humidity. The readings of a hair and film hygrometer are periodically compared with the readings of a more accurate device - a psychrometer, which is also used to measure air humidity.

4. B electrolytic In a hygrometer, a plate of electrical insulating material (glass, polystyrene) is covered with a hygroscopic layer of electrolyte - lithium chloride - with a binder material. When air humidity changes, the concentration of the electrolyte changes, and therefore its resistance; The disadvantage of this hygrometer is that the readings depend on temperature.

5. Action ceramic The hygrometer is based on the dependence of the electrical resistance of solid and porous ceramic mass (a mixture of clay, silicon, kaolin and some metal oxides) on air humidity.

6. Condensation A hygrometer determines the dew point by the temperature of a cooled metal mirror at the moment traces of water (or ice) condensing from the surrounding air appear on it. A condensation hygrometer consists of a device for cooling a mirror, optical or electrical device, which records the moment of condensation, and a thermometer that measures the temperature of the mirror. In modern condensation hygrometers To cool the mirror, a semiconductor element is used, the operating principle of which is based on the Peltier effect, and the temperature of the mirror is measured by a wire resistance or semiconductor micro-thermometer built into it

Electronic hygrometers

Electronic hygrometers can use different principles:

• optoelectronic - measuring the dew point using a cooled mirror (the mirror is frozen, then gradually heated, and this is how the dew point is determined);
• capacitive - measure the change in the capacitance of a polymer or metal oxide capacitor (they measure only from 5% to 95%, they age, but they are almost independent of temperature);
• resistive - use the effect of changing the conductivity of salts or conductive polymers depending on humidity
• measuring air conductivity (measures absolute humidity; calculating relative humidity also requires temperature measurement).

see also

Excerpt characterizing the Hygrometer

Designed to determine air humidity. There are several types of hygrometers (weight, hair, film and others), the operation of which is based on different principles.

Encyclopedic YouTube

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✪ Calibration of a hygrometer from the TermoKid kit - Doctor Komarovsky

✪ Lesson 190. Instruments for measuring humidity

✪ Psychrometer

Subtitles

Types of hygrometers

1. Weight(absolute) hygrometer consists of a system of U-shaped tubes filled with a hygroscopic substance capable of absorbing moisture from the air. A certain amount of air is drawn through this system by a pump, the humidity of which is determined. Knowing the mass of the system before and after measurement, as well as the volume of air passed through, the absolute humidity is found.

2. Action hair The hygrometer is based on the property of defatted hair, which can change its length when air humidity changes, which makes it possible to measure relative humidity from 30 to 100%. The hair is stretched over a metal frame. The change in hair length is transmitted to an arrow moving along the scale ( on illus.).

3. Film The hygrometer has a sensitive element made of an organic film, which expands when humidity increases and contracts when humidity decreases. The change in the position of the center of the film membrane is transmitted to the arrow. In winter, hair and film hygrometers are the main instruments for measuring air humidity. The readings of a hair and film hygrometer are periodically compared with the readings of a more accurate device - a psychrometer, which is also used to measure air humidity.

4. B electrolytic In a hygrometer, a plate of electrical insulating material (glass, polystyrene) is covered with a hygroscopic layer of electrolyte - lithium chloride - with a binder material. When air humidity changes, the concentration of the electrolyte changes, and therefore its resistance; The disadvantage of this hygrometer is that the readings depend on temperature.

5. Action ceramic The hygrometer is based on the dependence of the electrical resistance of solid and porous ceramic mass (a mixture of clay, silicon, kaolin and some metal oxides) on air humidity.

6. Condensation A hygrometer determines the dew point by the temperature of a cooled metal mirror at the moment when traces of water (or ice) condensing from the surrounding air appear on it. A condensation hygrometer consists of a device for cooling the mirror, an optical or electrical device that records the moment of condensation, and a thermometer that measures the temperature of the mirror. In modern condensation hygrometers, a semiconductor element is used to cool the mirror, the operating principle of which is based on the Peltier effect, and the temperature of the mirror is measured by a wire resistance or semiconductor micro-thermometer built into it

Electronic hygrometers

Electronic hygrometers can use different principles:

• optoelectronic - measuring the dew point using a cooled mirror (the mirror is frozen, then gradually heated, and this is how the dew point is determined);
• capacitive - measure the change in the capacitance of a polymer or metal oxide capacitor (they measure only from 5% to 95%, age, but are almost independent of temperature);
• resistive - use the effect of changing the conductivity of salts or conductive polymers depending on humidity
• measuring air conductivity (measures absolute humidity; calculating relative humidity also requires temperature measurement).

This article will introduce you to the instructions (operating manual) for psychrometric hygrometers of the VIT-1 and VIT-2 types, as well as about methods for disposing of psychrometric hygrometers.

Don’t forget that you can buy psychrometric hygrometers VIT-1 and VIT-2 from us at the best price.

Instructions (manual) for the operation of psychrometric hygrometers VIT-1 and VIT-2

Introduction
1. The instructions define safety measures when working with a hygrometer, preparing it for work and operating procedures, characteristic malfunctions And Maintenance hygrometer.
2. Specifications hygrometer, amendments to hygrometer thermometers, manufacturer's guarantees are given in the passport.

Indication of safety measures when working with a hygrometer

1. When working with a hygrometer, it is prohibited:

Subject the hygrometer to sharp shocks both during installation and during operation;

Wipe the thermometer scale and psychrometric table with solvents, acids and other similar liquids;

Overheat the thermometers of the VIT-1 hygrometer more than 45°C and the VIT-2 hygrometer more than 60°C. If overheated, the thermometer tanks will be destroyed.

2. When thermometers are destroyed, the thermometric liquid toluene is removed from surrounding objects hot water. Toluene is toxic, flammable, flash point is about 5°C.

Design and principle of operation of a hygrometer

1. A hygrometer is a device assembled on a base made of phenolic plastic or other materials with similar properties. Two thermometers with a scale, a psychrometric table, and a glass or plastic feeder filled with distilled water are attached to the base.The thermometer reservoir under the inscription "Humid." moistened with water from the feeder using a cambric or chiffon wick.
2. The method of measuring relative humidity with a psychrometric hygrometer is based on the relationship between air humidity and the psychrometric difference - the difference in the readings of the “dry” and “wet” thermometers, which are in thermodynamic equilibrium with the environment.By taking the thermometer readings and introducing corrections to their readings, the difference in thermometer readings is determined. Then, based on the readings of the “dry” thermometer and the difference in the readings of the “dry” and “moistened” thermometers, the relative air humidity is determined using a psychrometric table.

Preparing the hygrometer for use

1. Unpack the hygrometer and make sure that the device is complete in accordance with the passport.
2. Remove the feeder from the base. Fill the feeder with distilled water. Filling is done by immersing the feeder in a vessel with water, sealed end down.
3. Place the feeder on the base so that there is a distance of at least 20 mm from the edge of the open end of the feeder to the thermometer reservoir, and the wick does not touch the walls of the open end of the feeder.
Attention! Before installing the feeder in working position Moisten the wick by dipping the wet bulb reservoir into the water feeder.
4. Install the hygrometer in vertical position at eye level of the person working with it. The location where the hygrometer is installed must be free of vibrations and sources of heat or cold that would create a temperature difference between the lower, main reservoir and the upper reserve reservoir of more than 2°C.
5. The psychrometric table established on the base of the hygrometer is valid for a certain vertical speed air flow(aspiration rate) washing the hygrometer. The aspiration rate is indicated in the table. You can see the full psychrometric table for the VIT-2 hygrometer at the link.
6. Before measuring relative humidity, measure the aspiration rate directly under the hygrometer. Measure the aspiration rate using a vane anemometer U5 GOST 6376-74. It is possible to use the previously produced anemometer ASO-3, type B, GOST 6376-52. The measurement procedure is in accordance with the anemometer data sheet. The aspiration rate measured by an anemometer is rounded to tenths of m/s according to the arithmetic rounding rule. You can buy a VIT hygrometer aspiration device by clicking on.
7. Measure relative humidity with a hygrometer only after establishing the readings of the hygrometer thermometers. The minimum exposure time of the hygrometer in the measured environment is 30 minutes.

Operating procedure of a psychrometric hygrometer

1. Take readings from the “dry” and “wet” thermometers. When taking readings, the worker’s eye should be at the level of the horizontal tangent to the meniscus of the liquid so that the scale mark at the reference point is visible as a straight line.
2. The person working with the hygrometer must be at a distance from it where the scale marks are normally visible and be careful not to breathe on the thermometers during readings. When reading thermometers, tenths of a degree are first quickly counted, then whole degrees.
3. Determine the temperature using thermometers with an accuracy of 0.1 ° C, introducing corrections to the thermometers given in the hygrometer data sheet to the readings. Calculate the temperature difference between the “dry” and “wet” thermometers. Corrections are introduced by algebraic addition.
4. If there are no corrections in the passport for the readings made from the “dry” and “wet” thermometers, calculate the corrections by linear interpolation using two corrections related to the temperatures between which the reading from the thermometers lies.
5. Determine the relative humidity using the psychrometric table. The desired relative humidity will be at the intersection of the lines of temperature according to the “dry” thermometer and the temperature difference between the “dry” and “wet” thermometers.
6. If the table does not contain the resulting temperature difference between the “dry” and “wet” thermometers, use interpolation to determine humidity.If there is no dry-bulb temperature in the table, to determine humidity, use interpolation only for those areas of the psychrometric table in which a change in dry-bulb temperature of 1°C gives a change in relative humidity of more than 1%.
For the remaining areas of the table, round the dry-bulb temperature values ​​to the nearest table value using the arithmetic rounding rule.

An example of determining relative humidity by interpolation

1. Determine the temperatures using the “dry” and “wet” thermometers and the difference between these temperatures.

We accept Tc = 22.4°C, the temperature difference (Tc-Tv) is equal to: 22.4-16.3 = 6.1°C.

2. Determine the relative humidity for Тс=22.4°С and Тс-Тв=6.0°С, for this purpose by interpolating the relative humidity value according to the table for Тс from 22 to 23°С and Тс-Тв=6.0°С .

With an increase in Tg by 1°C, the relative humidity increases by 2%, therefore, an increase in Tg by 0.4°C will increase the relative humidity by (0.4x2)/1=0.8%.
For Тс=22.4°С and Тс-Тв=6.0°С, relative humidity is equal to: 48+0.8=48.8%. We accept "Fp" = 4.9%.
3. We determine the relative humidity for Тс-22.4°С and Тс-Тв=6.5°С, for which we interpolate the relative humidity values ​​according to the table for Тс from 22 to 23 and Тс-Тв=6.5°С.

For Тс=22.4° and Тс-Тв=6.5°С, the relative humidity, according to a calculation similar to point 2, is 44.8%. We accept "Fp" = 45%.
4. We determine the relative humidity for Тс=22.4°С and Тс-Тв=6.1°С, for which we interpolate the found values ​​of relative humidity for Тс-Тв from 6.0°С to 6.5°С at Тс= 22.4°C.

With an increase in Tc-Tv by 0.5°C, the relative humidity decreases by 4.0%, so an increase in Tc-Tv by 0.1°C will reduce the relative humidity by (0.1x4.0)/0.5= 0.8 %.49.0-0.8=48.2%. We accept "Fp" = 48%.

Typical malfunctions of psychrometric hygrometers and methods for their elimination

1. The design of the hygrometer includes parts made of glass, so protect the hygrometer from falls and sharp impacts.
2. If the feeder is destroyed, replace it with another one included in the hygrometer kit. To do this, remove the remains of the broken one and insert a new one, securing the feeder with a spring located on the back side of the hygrometer base. Either.
3. Thermometric fluid breaks are a repairable fault. If liquid ruptures occur in thermometers, repair them by carefully heating the thermometer reservoirs to the appropriate temperatures (V IT-1 no more than 45°C and hygrometer VIT-2 no more than 60°C. If overheated, the thermometer tanks will be destroyed.)

Maintenance of psychrometric hygrometers

1. The feeder must always be filled with distilled water in accordance with GOST 6709-72. Replenish the water in advance, preferably immediately after taking measurements or at least 30 minutes before starting humidity measurements.
2. Allow the use of boiled water, boiling time for at least 15 minutes. Fill the feeder with water pre-cooled to ambient temperature.
3. The wick on the reservoir of the “wet” thermometer should always be clean, soft and moist. If the dust level in the air is up to 5 mg/m³, change the wick once every two weeks, with higher dust levels as the wick gets dirty.
4. Before replacing, remove any dirty wick from the thermometer reservoir. Wipe the reservoir with a cotton swab moistened with warm water.
5. Take the wick from the hygrometer kit or cut the wick 60 mm long, if the wicks in the kit are given in the form of a blank, for 10 pieces. Moisten the wick in distilled or boiled water and pull it onto the thermometer reservoir so that you can tie it with a thread over the reservoir. The end of the tied wick above the tank must be at least 7 mm.
6. Prepare two loops of thread. Using one loop, pull the wick tightly over the thermometer reservoir and tie the threads. Place the second loop on the wick under the tank and gradually tighten it, all the time straightening the wick so that it fits tightly around the tank. Do not tighten the loop tightly, but so that it does not interfere with capillary wetting of the wick fabric on the thermometer reservoir.
7. To make a new wick, use cotton chiffon, bleached, undyed, technical without prohibition according to GOST 9310-75 or bleached cambric, mercerized, article 1402 NA according to GOST 8474-80. It is allowed to use cotton stocking cord, art. 494, OST 17-184-75.
8. Before making the wick, treat other types of chiffon or cambric as follows:

• wash in hot water(10 g of soda per 1 liter of water),
• boil in a solution of the same concentration for 1.5-2 hours,
• rinse in hot water, change the water until it is clean,
• dry and iron.

9. Sew the wick along the diameter of the thermometer reservoir using a simple machine seam. After trimming, the height of the seam should be no more than 1.5 mm.
10. Install the new wick and feeder on the hygrometer in accordance with the instructions.
11. The hygrometer is subject to initial and periodic verification. Primary verification is carried out upon release from production, periodic verification- once every two years in accordance with methodological instructions MI-737-83 "Psychrometric hygrometer type VIT. Methods and means of verification", approved by in the prescribed manner. Information about the verification of the hygrometer is given in the passport.

Rules for storing and transporting hygrometers

1. Store hygrometers in closed, dry rooms in a vertical or inclined position, in accordance with the inscription “Top” on the box, at a temperature from -60°C to +45°C. Do not store hygrometers less than 1 m from heat sources ( heating devices, various heaters, etc.).
2. Hygrometers in transport containers are transported by any type of transport, taking into account the temperature indicated above and subject to compliance with the rules for the transportation of goods for the corresponding type of transport.

Disposal of psychrometric hygrometers

Unlike mercury devices, recycling hygrometers is quite simpler: you just need to throw them away. On this moment There is no law that states that hygrometers must be disposed of in a special way.

If the hygrometer has expired, then there is no point in re-verifying it; it is much cheaper and more profitable to purchase it from us at affordable prices.