Homemade thermometer-hygrometer on SHT21. How to make a hair hygrometer with your own hands. Homemade humidity meter How to make a hygrometer at home What is the difference between a psychrometer and a hygrometer

Lyudmila Dudoladova

For our weather site, we decided to make a Christmas tree with pine cones. After all, an ordinary cone can turn into a unique weather forecasting device.

The fact is that cones tend to close or open depending on air humidity. When it's dry outside, bump "reveals" so that the wind can carry its seeds and scatter them as far as possible from the cone. And on the eve of rain or snow, when air humidity rises, the cone is usually closed to preserve the seeds until a more convenient time, since it is easier for the wind to transport them dry.

So we decided to make a Christmas tree with pine cones to monitor the weather at our weather site.

They cut out a Christmas tree from plywood, sanded it, painted it green color (the Dokuchaev family, Alina and Arseny, helped us with this)

Using decorative buttons and strong threads, we attached the cones to the Christmas tree.

Now we are looking forward to the rain, when the scales close, showing that air humidity has increased.

A pine cone is a unique phenomenon in nature; you just need to learn how to use it. I hope that by observing the cones, children will understand why they open and close.

Children should come to the conclusion that the pine cone is a natural weather predictor.

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The most common and simple device for measuring temperature and air humidity during the drying of wood in drying chambers ah is an electronic psychrometer.

Operating principle and short description: The psychrometer consists of two thermometers: “dry” and “wet”. The “dry” one is just a thermometer, and the “wet” one has a wick made of cotton fabric, the ends of which are lowered into a bath of water.

Due to the hygroscopicity of the fabric, the water from the bath rises and wets the entire wick. Due to the evaporation of water from the surface of the wick, the temperature of the “wet” thermometer decreases and a temperature difference arises between the “dry” and “wet” thermometers. This difference is called the psychrometric difference.

The lower the air humidity, the more speed evaporation, and hence the psychrometric difference. Thus, the “dry” thermometer shows the air temperature in the chamber, and the psychrometric difference characterizes the humidity.

Relative air humidity is determined by temperature and psychrometric difference using psychrometric tables. There are several tables, since the evaporation rate also depends on the air flow speed. For drying chambers, a psychrometric table is suitable for an air flow speed of 2 meters per second. As a rule, a psychrometric table is not used when drying wood, but the temperature and psychrometric difference are simply set in the drying mode.

How to make a psychrometer

Option 1. An easy-to-manufacture electronic psychrometer with a water addition system, made on the principle of an automatic drinking bowl, is shown in the top photo on the left. It is made on the basis of two identical resistance thermometers. We recommend using copper thermometers (the letter “M” is present in the designation: M50, M100, and so on) since they have a linear nominal static characteristic. When choosing thermometers, pay attention to the environment in which they are intended. If the thermometer is intended for use only in a gaseous environment, water from the wick may leak into the thermometer and render it unusable. You need to take thermometers that are designed to work both in air and in water.

The “dry” thermometer is attached to the chamber wall using a corner. For a “wet” thermometer, a bath is made from of stainless steel. You can use (if you have one) a ready-made bath made of heat-resistant plastic, aluminum or other corrosion-resistant material. It is not recommended to make a bath from “ferrous” metal, as it will quickly rust, the rust will “clog” the wick and the psychrometer will begin to give incorrect readings of the psychrometric difference.

You should not make an excessively wide or long bath. This will lead to increased evaporation from the surface of the water in the bath and you will have to add water more often, but you don’t need that. If you find a ready-made bath, but it is too large, then make a lid for it with a slot for the wick.

The “wet” thermometer is installed at a height of 2-3 centimeters from the surface of the water in the bath. This height should not be made too high; this will impair the wettability of the wick and the psychrometer will give incorrect readings.

The tank for adding water to the bath is made of ordinary aluminum canister. Canisters made of polyethylene and other plastics with a low melting point should not be used. The temperature in the chamber rises to 70 - 75 degrees. At this temperature, the walls of the canister made of such materials soften, lose their rigidity, the canister simply flattens and almost all the water flows out of it.

All production of the tank comes down to drilling a hole in the lid of the canister and installing a fitting on the lid (which can also be bought at a hardware store). When installing the fitting, it is recommended to coat the edge of the hole in the cover with automotive silicone sealant. This will ensure the necessary tightness of the connection. A hose is put on the fitting, if necessary, the hose is tightened with a clamp - the tank is ready.

How and why it works. Pour water into the canister, screw the lid tightly, lower the end of the hose into the bath and turn the canister over. Water will pour into the bath until it closes the hole in the hose, after which the flow of water will stop. It's simple: the canister is sealed, water is poured out until the free space in the canister is taken up by air entering through the hose. As soon as the air flow stops, the water flow stops. In the future, due to evaporation, the water level in the bath will decrease, the hole in the hose will open and a new portion of water will pour into the bath. This will continue until the water in the canister runs out.

The main disadvantage of option 1. When drying wood, a lot of water will evaporate from the bath. From our experience, 10 liters of water will last for 3 - 5 days (depending on the size of the bath, the drying mode and its stage). That is, as a rule, there is not enough water in the canister for all drying, so you have to stop drying, open the drying chamber and pour water into the canister. This in itself is neither convenient nor desirable, and if the psychrometer is also in hard to reach place...
Therefore if:

1. The drying chamber is located in a heated room.
2. There is a heated room next to the cell.
3. The psychrometer is installed in a hard-to-reach place.

Option 2 (middle and bottom photos). Everything is the same as option one, just adding another bath. This bath, together with the canister, is placed in an easily accessible place in the chamber (for example, near technological door) or in warm room outside the camera. The tank bath (in the middle photo) and the psychrometer bath (in the bottom photo) are installed at the same level and connected to each other with a hose. As a result, the water level in both baths will always be the same (property of communicating vessels). This option is a little more complicated and more expensive: you will have to make not one, but two baths, buy not one, but three fittings and more hoses will be required. But the ease of use will quickly outweigh the costs.

The main mistake with this option is that if the hose is laid incorrectly, it becomes “aired” and water from the tank bath stops flowing into the psychrometer bath. The rule for laying the hose is simple: only one sag is allowed. If there are at least two of them, then an air plug may form in the upper part between them.

The advantages of option two are obvious: you can add water without entering the chamber and without stopping the drying; you can check the remaining water in the canister at any time.

Water. Distilled water is recommended to power the psychrometer. When drying hardwoods that have a long drying time, this condition is mandatory. When drying easily drying rocks, some deviations are possible. If tap water soft, then you can use it, but after each drying you need to wash the wick in running water. If the water is hard, you can use softened water. Installations for water softening are available at any large boiler house; water can be taken from them. What to do if the water is hard and there is no other water? Collect in summer rainwater, melt the snow in winter. It is not difficult.

Wick. The wick should be made only from natural cotton fabrics: chintz, cambric, batting, and so on. You can use regular gauze, folded into four layers.
It is recommended to check the condition of the wick before each drying. A clogged (salty) wick becomes hard to the touch. In this case, it must be removed and washed in running water (or replaced).
The wick should cover the entire working part of the thermometer. It is recommended to secure the wick to the thermometer, for example, with wire (see photos).

Place of installation of the psychrometer determined by the design of the drying chamber. For the chamber described in the article “Requirements for the design of drying chambers”, it is recommended to install the psychrometer on the wall of the chamber on the pressure side (from the side where the drying agent enters the stack of lumber), at a height of about 1.5 meters, in the middle of the length of the chamber.

Special moisture meters are used. Today there are needle, contact and chip modifications. In terms of parameters, they are quite different. However, there are not many manufacturers of moisture meters on the market. The main companies include, first of all, EMCO and Valcom. On average, a good moisture meter on the market costs around 1,500 rubles.

How to do it yourself?

If necessary, you can make a moisture meter for wood with your own hands. Its circuit includes a dielectric-type sensor. The device will also require a compact generator. Its maximum frequency parameter must be no more than 30 MHz. Contacts for homemade model It is more advisable to select needle-shaped ones. Also, to make a moisture meter for wood with your own hands, you will need a three-channel type microcircuit.

The device should be in the region of 3.5 F/m. The microprocessor for the model is selected with a pulse amplifier. Probes are most often used of the tubular type. It is more advisable to select a lowercase display. Compared to text counterparts, it is simpler. The electrodes used in moisture meters are capacitive ones. In turn, the catcher will need to be installed resistive. Lastly, batteries are selected for the model. In this case, you can use regular AA batteries.

Contact models

Contact wood moisture meters are well suited for working with plywood and parquet. Additionally, in the construction industry, devices are used to determine the humidity of panels. If we talk about contractual features, then low-frequency generators are used in the devices. The probes themselves are installed in a tubular type.

The dielectric constant of most moisture meters does not exceed 3 F/m. Maximum temperature models of this type are capable of holding at 40 degrees. The display is used in both line and text types. Many modifications are equipped with temperature sensors. Many devices have a calibration function. On average, a high-quality moisture meter costs around 2 thousand rubles.

Needle moisture meters

Needle moisture meters for wood are usually used for pine or spruce. Sensors in all configurations are of the dielectric type. If we talk about parameters, then the measurement accuracy generally fluctuates around 0.2%. The maximum humidity threshold for devices does not exceed 35%. Minimum permissible temperature for models is 0 degrees. Microprocessors in many devices are used with amplifiers. The average price for a wood moisture meter (needle type) is around 1,200 rubles.

Probe devices

Probe moisture meters for wood are mainly manufactured by the Valcom company. If you believe the opinion of experts, then their parameter is extremely low. Generators in devices are used with a frequency of 20 MHz. The catchers themselves are installed of the resistive type. The minimum humidity threshold for models does not exceed 5%. In turn, the devices are located at level 1 RN. Displays of moisture meters are often used in line type. Some modifications are equipped with thermometers. The calibration function in devices is quite rare. You can find a model of this type on the market for 2 thousand rubles.

Model EMCO AR

In the construction industry, the presented moisture meter is in great demand. It is ideal for working with parquet and panels. This moisture meter is also equipped with a thermometer. Another advantage of the modification can be safely called the presence of needle-type contacts. The manufacturer provides a three-channel microcircuit for the model, so wood moisture is measured quickly. The electrodes are of the capacitive type.

The maximum humidity threshold does not exceed 40%. In terms of size, this moisture meter is very compact and belongs to the class of portable devices. According to the documentation, its weight without batteries is 80 g. The resolution of the model is at the level of 1.3 pH. The maximum permissible temperature of the model is exactly 35 degrees. The presented device must not be used in cold weather. The measurement accuracy fluctuates around 1.4%. In stores, this device can be found for 2100 rubles.

Devices for determining moisture EMCO MP500

This moisture meter is equipped with a dielcometric type sensor. If you believe customer reviews, the resolution of the device is quite high. The generator itself is used at 22 MHz. According to the documentation, the maximum permissible temperature is 40 degrees. The display in the device is of text type.

The batteries are 1 mAh, so they last a long time. In this case, the catcher is provided by the manufacturer as a resistive type. If you believe the reviews of experts, then problems with determining the importance of wood chips do not arise. The maximum measuring depth is 10 mm. The user can purchase the presented moisture meter for 1,400 rubles.

Model "Valkom EM4806"

This moisture meter for hardwood, among other models, is distinguished by a high resolution parameter at the level of 1.3 pH. All this suggests that the device works perfectly at temperatures below 10 degrees. In this case, the measurement accuracy indicator is at 0.2%. The maximum permissible humidity threshold is 30%.

The catcher in the device is of a resistive type. The microcircuit is a three-channel one, and the generator is installed as a low-frequency one. According to the documentation for the device, the case is equipped with an IP 62 protection system. The presented model weighs exactly 80 g. The moisture meter’s memory is enough for 30 thousand measurements. The user can buy it for 1,500 rubles.

Reviews about "Valkom M804"

This wood moisture meter mostly receives good reviews. The main advantage of the model lies in its compactness. If we talk about more design features, it is important to note that it uses probe contacts. There are two sensors directly in the housing. Thus, the measurement accuracy is quite high.

The manufacturer provides the probe in the device with a tubular type. The resolution of the device fluctuates around 1.3 pH. The maximum humidity threshold, according to the documentation for the moisture meter, is 35%. Today you can buy this model for 2 thousand rubles.

Opinion about "Valkom AS101"

The presented moisture meter is in great demand in construction safra. First of all, mention should be made of a high-quality generator, which is installed with a frequency of 33 MHz. In this case, the sensor is of a dielectric type. The contacts, in turn, are needle-shaped. If you believe the reviews of experts, the measurement accuracy of the model is high.

It can be used for parquet and panels. The minimum permissible temperature of the device is 0 degrees. The resolution indicator is 1 pH. The catcher itself in the device is installed of a resistive type. The microprocessor is used with a switching amplifier. The maximum humidity threshold of the device is at 40%. You can buy this moisture meter for only 1,400 rubles.

Description of "Ectech MO280"

This portable moisture meter features a protected housing. It uses a low-frequency sensor. In turn, the contacts are needle-shaped. The presented copy has a calibration function. Temperature environment with help of this device can be determined. It is also important to mention the high resolution of the model.

The measurement accuracy in this case is 0.3%. The maximum humidity threshold allowed by the model is 45%. The microprocessor is provided by the manufacturer with an operational amplifier. Thus, data processing does not take much time. The memory of the presented modification is enough to make more than 20 thousand measurements. You can buy this moisture meter in a store for 1,300 rubles.

Model "Ectech MS60"

These wood moisture meters are often used by professional builders. They can work even at temperatures of 0 degrees. The model uses a high-quality case protection system. If you believe consumer reviews, the device is quite simple to use. The batteries for the model are selected with a capacity of 1.2 mAh.

According to many owners, they last a long time. The probe of the presented moisture meter is of a tubular type. The microcircuit in the case is three-channel. This modification is equipped with a thermometer, and this pleases many buyers. If we talk about the parameters, then the measurement accuracy is at around 0.3%, and the resolution of the device is only 1.2 pH.

It is prohibited to operate the device at temperatures above 35 degrees. Maximum permissible humidity equals 40%. These moisture meters are sold on the market at prices starting from 2 thousand rubles.

The level of ambient air humidity can affect not only a person’s well-being, but also the condition household appliances, furniture and products. The amount of moisture in the air depends on the climate of the region or man-made factors.

The norm for a healthy person is considered to be air humidity from 30 to 60%. To create an optimal indoor microclimate, special humidifiers or dehumidifiers are used, as well as air conditioners with automatic moisture level control functions.

Use special instruments to measure:

• hygrometers;
• psychrometers.

A hygrometer is one of the measuring instruments that can be used to determine the level of humidity.

Additional information: Swiss scientist in 1783 Horace de Saussure designed the first hair hygrometer, but Leonardo da Vinci began working on the invention of this meter back in 1400.

There are several types of hygrometers:

• hairline;
• weight;
• condensation;
• electronic;
• electrolytic;
• film;
• ceramic.

Each of the devices has a special operating principle. For example, the design of a hair hygrometer is made up of a system of U-shaped tubes. They are filled with a special substance that absorbs water vapor. Using a pump, air is supplied through this system and its humidity is determined.

The most accurate measurement is a condensation hygrometer. It measures the amount of condensation that forms on a glass surface after it is exposed to sunlight. The operating error of such a device is very low.

A psychrometer is another measure of ambient air humidity.

Types of psychrometers:

• August psychrometer (station);
• Assmann psychrometer (aspiration);
• remote psychrometer.

The August Psychrometer is one of the most famous instruments for measuring humidity. The structure of this structure is quite simple. The design of the psychrometer consists of two identical thermometers attached to one stand. One of them is called dry, it shows the temperature in the room.

The second thermometer is called a wet or wet thermometer. The end of this thermometer in the form of a cover is wrapped with cambric cloth or gauze, the end of which is lowered into a reservoir of water located on the back side of the psychrometer structure.

If the end of a wet bulb thermometer is lowered into a tank, it will indicate the temperature of the water there, not the temperature of the air that circulates above it. Therefore, it is necessary to take into account that the distance between the vessel and the end of the measuring device should be about 3 - 4 centimeters.

The water on the piece of cloth evaporates, causing the wet bulb temperature to drop until the thermometer reads the temperature at which steam becomes saturated. At this point, the wet bulb reading will represent the actual ambient temperature.

Determining air humidity in a certain room using a psychrometer takes a little time. To do this, the device is placed in a place isolated from contact with sun rays and extraneous thermal influences for 10 - 15 minutes, after which the measurement results of each of the thermometers of the device are recorded.

The thermometer scale is divided from - 25˚ to + 50˚ into intervals of 0.2 degrees.

How to use a psychrometric chart

To determine the humidity level based on psychrometer data, a special psychometric table is needed. The first column of the table shows the dry bulb temperature in ˚C. The first line shows the difference between the temperature readings of both thermometers. Relative air humidity is calculated at the intersection of the result of the first column and the first row of the psychometric table.

What are the pros and cons of a psychrometer?

The main advantage of the psychrometer is its simple structure. Accordingly, determining air humidity using a psychrometer is much simpler compared to other measuring devices. Plus, it is much cheaper to manufacture than any other device.

But besides the positive aspects, the psychrometer also has disadvantages. The readings of this measuring instrument are greatly influenced by the movement of the surrounding air. That is, the higher the air speed at the measurement location, the greater the difference in the final result of both psychrometer thermometers. This error was corrected in an aspiration-type psychrometer or, as it is also called, an Assmann psychrometer.

What is special about the Assmann psychrometer?

The Assmann psychrometer is a much more complex and more reliable device for measuring air humidity. Both thermometers of the design are located with their lower ends in a special metal case, which protects them from sunlight, thermal influences, and also from various damages. The air moves at a constant speed due to the operation of the fan. This fan, also known as an aspirator, blows the thermometers at a speed of 2 m/sec.

Determination of humidity using this psychrometer: the device is suspended at the test site at a height of 1.5 m from the floor; results are obtained after 10 - 15 minutes in winter and after 4 - 5 minutes in summer.

What the August psychrometer and Assmann psychrometer have in common is that both have glass-mercury thermometers in their design. The disadvantage of these devices is their fragility and, accordingly, the inability to carry out measurements remotely.

How does a remote psychrometer differ from other devices?

A remote psychrometer is another example of a device for measuring humidity. The design of this measuring device uses electronic devices such as a resistance thermometer or thermistors.

Main types of remote psychrometers:

• manometric;
• electric.

A manometric psychrometer is one or two manometric type thermometers. Electronic psychrometers, like all other remote meters, use silicon transistors that replace dry and wet bulb sensors.

What is the difference between a psychrometer and a hygrometer

The main difference between these devices for determining humidity is the principle of their operation. The functions of a hygrometer include measuring not only air humidity, but also the humidity of various solids.

The readings of a psychrometer, despite the simplicity of its design, are always more reliable, which is why the notes to the instructions of some hygrometers recommend checking the readings using a psychrometer.

How to find out air humidity without measuring instruments

To carry out this experiment, you will need a regular glass, some water and a refrigerator. Place a glass of water in the refrigerator for several hours. cold water. When the temperature of the liquid in the vessel reaches 3–5˚С, the glass is placed in the room where air humidity will be measured.

If the air in the room is very dry, then condensation will be observed on the surface of the glass, which will disappear after 5 - 10 minutes of observation. If the air in the room is very humid, then large drops of condensation form on the walls of the glass within 5–10 minutes. If none of the two previous options are observed, the air in the room is of medium humidity.

How to make an air humidity meter with your own hands

A psychrometer is a fairly simple invention in its design, so anyone can make it themselves.

Necessary materials:

• two alcohol thermometers;
• a small piece of cambric fabric;
• several wooden slats;
• small screws;
• glass jar.

For the psychrometer stand, you need to take a small wooden plate measuring 50 mm wide and 120 mm long. We attach a strip to it with screws, the length of which depends on the length of the measuring instruments used. Another bar is attached perpendicular to it, on which the thermometers will be held.

For compactness and highest accuracy of indicators, thermometers should not be placed at a large distance from each other.

The base of the device can be connected to the stand by drilling a small hole in it, or you can use PVA glue. After the psychrometer body is assembled, the lower balloon of one of the thermometers is wrapped with cambric fabric. The end of the fabric is lowered into a vessel containing a non-freezing liquid.

When checking the performance of a manufactured device, you should check the results of the factory meter and compare both indicators. In the future, to determine the level of air humidity, it is necessary to use a special psychrometric table.

Using a minimum of materials and free time, the owner finished product will receive useful tool to measure air moisture levels.

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A hygrometer is a moisture meter for an incubator that can be used to control the air humidity inside the incubator. But during different periods of incubation, humidity indicators should differ: in the first week - 65-75%, in the second - 40-50%, in the third - 75% (data for hatching chickens is indicated).

Devices that are used for household incubators are characterized by low cost - from 500 to 1000 rubles per product.

Principle of operation

Electronic hygrometer

To measure humidity, lower an incubator hygrometer into the container through a special hole. It is fixed in a suspended state for 5-10 minutes.

After the specified time, humidity indicators should appear on the display of the moisture meter. If you open the incubator lid to lower the device, you need to wait about an hour to get accurate data.

For long-term and productive operation of the device, it is protected from falls and shocks, and the wire to which the sensor is connected is not pulled.

In order for the device to function properly, you must comply with temperature regime(from -40 to +70 degrees). You should also reduce the likelihood of dust, dirt and various liquids coming into contact with the device.

The humidity sensor for the incubator works according to a specific algorithm:

• If the humidity level inside the container, which was set by the poultry farmer, has changed, the equipment operates and signals possible problems.
• After this, the farmer must study the humidity indicator, add or remove the amount of water in the incubator.
• After a few hours, you need to check the sensor readings again. You need to constantly monitor it so that there is a stable level of humidity in the chamber.

Types of hygrometers for incubators

Meet different types hygrometers, which have their own characteristics, individual type work, advantages and disadvantages.

The following varieties are distinguished:

1. Weight hygrometer for incubator. It consists of several combined tubes, inside of which there is a hygroscopic substance that absorbs moisture. Using this system, a small amount of air is drawn in and its humidity is determined.
2. Hair moisture meter. It is known that hair changes length when air humidity changes. Due to this it is possible to measure relative humidity– from 30% to 100%. The hair is pulled onto a metal frame, and if the humidity level changes, the data is transmitted to a needle, which moves along the scale.
3. Film air humidity sensor for incubator. Equipped with a special element made of organic film. When humidity increases, it stretches, and when it decreases, it contracts.
4. Ceramic. Its work is based on the dependence of the resistance of a ceramic part on air humidity.

How to choose the right hygrometer, what to look for

To choose a good hygrometer for an incubator, you need to study its technical data. First, pay attention to the pressure parameter, which can be relative (RH) or absolute (g/m3).

The choice of equipment also depends on the size of the incubators. If the container is small, for 40-50 eggs, you can use the simplest device. But for incubators with 100 or more eggs, it is recommended to buy more powerful hygrometers.

Typically, hygrometer readings are off by about 5%. If you need a more accurate device, then preference should be given to optical types. In order for equipment to last more years, when buying it, you need to look at its level of protection.

Measured on the IP scale. The higher its value, the more resistant the device is to dust, dirt and water.

Hygrometer models

If you are wondering which is the best of all the options, then this title is occupied by the MAX-MIN device (3 in one). This is not just a humidity sensor. The plastic case contains a thermometer for the incubator, which shows the temperature values ​​as accurately as possible. The device is also equipped with a clock and alarm.

In addition, an additional MAX-MIN TH218A humidity sensor can be connected to it. By placing it directly inside the housing, you don’t have to worry about disturbing the internal microclimate in the incubator.

The sensor readings are as accurate as possible with an error of 1%. If the humidity level changes, it will work sound alarm, which will allow the poultry farmer to quickly find out about violations.

The thermometer lets you know if the temperature sensor is working properly. After all, if deviations from the norm are too large and quite frequent, then there is a high probability of problems in its functioning. It needs to either be replaced or configured correctly.

An alarm clock is also an important indispensable tool. Especially if you have to work with a manual incubator, when you need to turn the eggs yourself. By setting it to fire every 4-5 hours, you will never forget that you need to perform masonry manipulations.

The screen of the equipment is large, divided into three segments (for humidity, temperature and clock). All indicators are visible from afar, highlighted in bright colors. Therefore, you don’t have to approach the incubator every time, because data on its operation can be viewed from a distance. I am especially pleased with the cost of the device - only 600 rubles.

How to make a hygrometer with your own hands

And although a hygrometer for an incubator is inexpensive, you can make it yourself. A DIY moisture meter for an incubator gives more accurate readings than its store-bought counterparts.

To do homemade device, necessary:

• Take two mercury thermometer for measuring air temperature, water. You also need to take a board on which both thermometers will fit.
• Both thermometers need to be attached to the board parallel to each other. A vessel with distilled water is placed under one of them.
• The mercury ball of one thermometer must be carefully wrapped in a cloth without contacting it. Then the fabric should be tied with thread, not too tightly. This thermometer is called wet, and the second is called dry.
• The edge of the fabric should be lowered into water by 5-7 mm.
• The indicators of both thermometers are compared with each other and using the table they find out the relative air humidity in the incubator.

Sometimes you have to spray the eggs with water to increase the humidity in the chamber. But this technique should only be used in the case of waterfowl eggs. For the rest of the embryos, a humidity of 50-60% is enough. You can calculate the humidity indicator using the table below.

A hygrometer is a device for measuring humidity - everyone knows this. It is also well known to everyone that recently it has become a permanent, and for many, a necessary (not just a decoration) attribute of most saunas and baths.

Experienced lovers of bath procedures say: “The best hygrometer is the ears!” However, then they usually add: “... and experience.” Of course, experience is a great thing, but beautiful and reliable device on the wall of a modern steam room (sauna) will never hurt.

Most of the numerous modern hygrometers can be divided into three main groups.

1. Electronic hygrometers.

Very often, these devices are built into control panels for steam generators and humidifiers. The reliability and accuracy of operation of such products largely depends on the circuit design and the quality of the components.

2. Psychrometric hygrometers.

The principle of operation of devices of this type is based on changing the difference between the readings of a wet and dry thermometer, which depend on the humidity of the air in the room; they then directly measure the humidity using special psychrometric tables. Temperature is measured based on dry bulb readings.

Such hygrometers are rarely used in sauna baths.

3. Mechanical hygrometers.

The principle of operation of such devices is based on the property of degreased hair to change its length when the humidity of the surrounding air changes. When the length of the hair changes, the pulley mechanically connected to it rotates, and the end of the arrow moves along the scale (see Fig. 1).

Rice. 1. Diagram of a hair hygrometer.

Today, instead of good old hair, a specially treated synthetic thread is usually used as a sensing element. Mechanical hygrometers operate quite reliably over a wide temperature range of at least +10°C to +120°C), measuring humidity fairly accurately in the range from 30% to 100%. Such mechanisms are now installed in the vast majority of relatively inexpensive bath hygrometers and combined thermometer-hygrometers. Most often, bath hair hygrometers and bimetallic thermometers-hygrometers operate stably and provide fairly reliable readings with quite acceptable - from a practical point of view - accuracy.

However, like any mechanical device, the hair hygrometer does not like rough handling, especially strong shaking or sharp blows. Sometimes such a device can begin to completely indecently overestimate or underestimate readings, even just after a long stay in severe frost.

If it is possible to compare the readings of a hair hygrometer with the readings of a reference device, then if there are serious discrepancies, the readings of a mechanical hygrometer can be easily corrected. This can be done using a screwdriver through the hole on back cover. You should insert a screwdriver into the slot of the adjusting screw on the support of the measuring mechanism and, turning it carefully, move the arrow to the desired reading on the instrument scale. Usually this is enough to restore the functionality of the hygrometer.

If it is not possible to compare the readings of a hair hygrometer and a known working precision device, then you can try to make adjustments using another method available at home. It should be borne in mind that it is best to check the operation of a thermometer-hygrometer at a temperature as close as possible to what would usually be in the steam room.

To check and adjust you will need: a teapot, transparent plastic bag, a stand for the appliance under test to place it at the level of the kettle spout (for example, a shallow saucepan). Next we proceed as follows. We place the device in a bag and make a small hole in the bag for steam to escape (photo 1). We connect the bag to the spout of the kettle and secure this connection with threads or an elastic band (photo 2). We put it all on the stove and light the fire (photo 3).

After some time, the water in the kettle will boil, the scales will fog up, the temperature will begin to rise, and the thermometer needle will set around 95-100°C, the hygrometer needle will also begin to deviate and reach its maximum (photo 4).

If within 3-5 minutes the hygrometer needle does not change its highest position, we can assume that the maximum point has been reached. The thermometer needle should show 95-100C, that is, a temperature close to the boiling point of water. If the value is different, for example, 80°C, you need to adjust the thermometer readings using a screwdriver through the hole on the back cover. This can be done directly through the package. The most important thing is not to get scalded!

If necessary, the position of the hygrometer needle is also adjusted, setting it to a value close to the maximum - 95-100%.

Now you can carefully remove the device from the bag, dry it and... go to work. The photo at the beginning of the article shows the readings of a household electronic thermometer-hygrometer and a hair bath thermometer-hygrometer tested using a kettle. The picture was taken the next day after checking, adjusting and drying the device for 24 hours - the readings of both devices are almost completely identical. Thus, this method allows you to quite accurately adjust the hygrometer at temperatures close to operating temperatures.

You can, of course, buy a thermometer-hygrometer, but it’s interesting and cheaper to make one yourself. In view of the excess of free thermal sensors and some other parts lying around idle, I decided to assemble this device needed in everyday life on the ATmega168V and SHT21. Read on for more details...

In the circuit, the sensor measures not only temperature, but also humidity. For me, the practical benefit of this feature is doubtful, but since it might be useful to someone, I decided to use it too. By the way, this is probably one of my longest projects (the software took a month to write!). Development was delayed mainly due to lack of free time and the buggy nature of some compiler from some company, but first things first...

The thermometer does not have any exotic capabilities - it simply shows temperature with humidity and a battery charge indicator. The data is displayed on the screen of a Siemens phone. I wrote earlier about how to connect it to a microcontroller (link at the end of the article). I chose this display as the most economical of all the ones I have + it is very thin and easy to control using a microcontroller. The only drawback: at a voltage below 2 volts, you can’t make out anything on it (although the controller works stably even at 1.8 V). That is why, when the battery is discharged to approximately 2 volts, a full battery indicator will be shown on the screen.

I took the time to draw (or rather sketch!) large beautiful numbers to display temperature and small, strict numbers to display humidity. What came out of this is clearly visible in the pictures.

Printed circuit board? No, have not heard:-). And why is she here if the details are missing once or twice. Good installation+ high-quality body and nothing is scary for this device. Moreover, I don’t plan to play football with them. All parts are connected with MGTF wire f-0.07 mm - the best installation wire in the world :). It’s just a little difficult to clean, but that’s just its only downside. I do not have any holder for the battery (due to limited space in the case), so the wires were soldered directly. I used soldering acid as a flux, because I didn’t want to solder with rosin at the relatively low temperature of the soldering iron, and I didn’t dare overheat the battery. All open contacts were carefully insulated with tape before putting the whole thing into the case. I bit off the extra legs of the controller (with the exception of those needed for firmware), and glued the body itself with superglue. By the way, the display also rests on it. As a result, the outside of the device looks much more beautiful than the inside :) It is also important not to forget to make a hole in the housing for the sensor if we want to measure the temperature outside the device’s body. The case itself is called G1906 (~$2), and this is what it looked like at the very beginning of my mockery of it:

The most difficult thing here is to make a rectangular hole like this. I did this: first I drew a rectangle and then I made holes along the contour with a regular drill which I drill boards with. After drilling 100500 holes, the rectangle is broken out and the edges are cleaned with a file. By the way, this is probably the smoothest hole I’ve ever made :)

Everything is quite simple and banal except for the small highlight of power management. I saw it in some magazine: We close the button, the device starts, sets a logical one on the leg, thereby maintaining the transistor in the open state, and after five seconds a logical zero appears on the leg and the transistor closes, cutting off the power to the entire device. Everything is ingenious and simple. Before use, you need to twist the resistor R4 so that at three volts of the supply voltage there is a voltage of 1.1 volts on its brush connected to PC0. Otherwise, the charge level will not be displayed correctly. It is best to use a multi-turn resistor; it is easier for them to adjust tenths of a volt. The microcontroller operates at a frequency of 8 MHz from an internal oscillator. In total, the device consumes 5 mA, which means that the batteries (CR2032) will last a long time.

And now we get to the most interesting part of the project: the software. Taking this opportunity, I would like to pour out tons of hatred on the creators of the micropascal compiler. I have never seen such curvature before. After my program began to take up more than ~10kb of flash memory, inexplicable glitches began, which I skillfully overcame by cramming in various crutches. In my program you can find the unnecessary UART initialization (it doesn’t work without it), setting up ports through assembler inserts, as well as some other interesting things! I no longer write in micropascals, which is what I wish for you.

Ready-made thermometers and thermometer-hygrometers can be purchased, for example, here:

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The other day an old friend contacted us. He lives in a private house and a couple of times unknown persons tried to visit him without an invitation. There is a need to install an alarm system. It turned out to be too expensive to put the house on the remote control. It seemed like the optimal solution was to simply notify the owner with a call to his mobile phone when one of the motion sensors was triggered.

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A hygrometer is a moisture meter for an incubator that can be used to control the air humidity inside the incubator. But during different periods of incubation, humidity indicators should differ: in the first week - 65-75%, in the second - 40-50%, in the third - 75% (data for hatching chickens is indicated).

Devices that are used for household incubators are characterized by low cost - from 500 to 1000 rubles per product.

Principle of operation

Electronic hygrometer

To measure humidity, lower an incubator hygrometer into the container through a special hole. It is fixed in a suspended state for 5-10 minutes.

After the specified time, humidity indicators should appear on the display of the moisture meter. If you open the incubator lid to lower the device, you need to wait about an hour to get accurate data.

For long-term and productive operation of the device, it is protected from falls and shocks, and the wire to which the sensor is connected is not pulled.

In order for the device to function normally, the temperature regime must be observed (from -40 to +70 degrees). You should also reduce the likelihood of dust, dirt and various liquids coming into contact with the device.

The humidity sensor for the incubator works according to a specific algorithm:

• If the humidity level inside the container, which was set by the poultry farmer, has changed, the equipment operates and signals possible problems.
• After this, the farmer must study the humidity indicator, add or remove the amount of water in the incubator.
• After a few hours, you need to check the sensor readings again. You need to constantly monitor it so that there is a stable level of humidity in the chamber.

Types of hygrometers for incubators

There are different types of hygrometers, which have their own characteristics, individual type of operation, advantages and disadvantages.

The following varieties are distinguished:

1. Weight hygrometer for incubator. It consists of several combined tubes, inside of which there is a hygroscopic substance that absorbs moisture. Using this system, a small amount of air is drawn in and its humidity is determined.
2. Hair moisture meter. It is known that hair changes length when air humidity changes. Due to this, you can measure relative humidity - from 30% to 100%. The hair is pulled onto a metal frame, and if the humidity level changes, the data is transmitted to a needle, which moves along the scale.
3. Film air humidity sensor for incubator. Equipped with a special element made of organic film. When humidity increases, it stretches, and when it decreases, it contracts.
4. Ceramic. Its work is based on the dependence of the resistance of a ceramic part on air humidity.

How to choose the right hygrometer, what to look for

To choose a good hygrometer for an incubator, you need to study its technical data. First, pay attention to the pressure parameter, which can be relative (RH) or absolute (g/m3).

The choice of equipment also depends on the size of the incubators. If the container is small, for 40-50 eggs, you can use the simplest device. But for incubators with 100 or more eggs, it is recommended to buy more powerful hygrometers.

Typically, hygrometer readings are off by about 5%. If you need a more accurate device, then preference should be given to optical types. In order for equipment to last more years, when buying it, you need to look at its level of protection.

Measured on the IP scale. The higher its value, the more resistant the device is to dust, dirt and water.

Hygrometer models

If you are wondering which is the best of all the options, then this title is occupied by the MAX-MIN device (3 in one). This is not just a humidity sensor. The plastic case contains a thermometer for the incubator, which shows the temperature values ​​as accurately as possible. The device is also equipped with a clock and alarm.

In addition, an additional MAX-MIN TH218A humidity sensor can be connected to it. By placing it directly inside the housing, you don’t have to worry about disturbing the internal microclimate in the incubator.

The sensor readings are as accurate as possible with an error of 1%. If the humidity level changes, an audible alarm will sound, allowing the poultry farmer to quickly become aware of any violations.

The thermometer lets you know if the temperature sensor is working properly. After all, if deviations from the norm are too large and quite frequent, then there is a high probability of problems in its functioning. It needs to either be replaced or configured correctly.

An alarm clock is also an important and indispensable tool. Especially if you have to work with a manual incubator, when you need to turn the eggs yourself. By setting it to fire every 4-5 hours, you will never forget that you need to perform masonry manipulations.

The screen of the equipment is large, divided into three segments (for humidity, temperature and clock). All indicators are visible from afar, highlighted in bright colors. Therefore, you don’t have to approach the incubator every time, because data on its operation can be viewed from a distance. I am especially pleased with the cost of the device - only 600 rubles.

How to make a hygrometer with your own hands

And although a hygrometer for an incubator is inexpensive, you can make it yourself. A DIY moisture meter for an incubator gives more accurate readings than its store-bought counterparts.

To make a homemade device, you need:

• Take two mercury thermometers to measure air temperature and water. You also need to take a board on which both thermometers will fit.
• Both thermometers need to be attached to the board parallel to each other. A vessel with distilled water is placed under one of them.
• The mercury ball of one thermometer must be carefully wrapped in a cloth without contacting it. Then the fabric should be tied with thread, not too tightly. This thermometer is called wet, and the second is called dry.
• The edge of the fabric should be lowered into water by 5-7 mm.
• The indicators of both thermometers are compared with each other and using the table they find out the relative air humidity in the incubator.

Sometimes you have to spray the eggs with water to increase the humidity in the chamber. But this technique should only be used in the case of waterfowl eggs. For the rest of the embryos, a humidity of 50-60% is enough. You can calculate the humidity indicator using the table below.