How to make a hygrometer from a napkin. Homemade thermometer-hygrometer on SHT21
Ludmila Dudoladova
For our meteorological site, we decided to make a Christmas tree with cones. After all, an ordinary cone can turn into a unique device for weather forecasting.
The fact is that cones tend to close or open, depending on air humidity. When it's dry outside "revealed" so that the wind can spread its seeds and scatter 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 keep the seeds until a more convenient time, since it is easier for the wind to carry them dry.
So we decided to make a Christmas tree with cones to monitor the weather at our weather site.
A Christmas tree was cut out of plywood, sanded and painted green. (the Dokuchaev family, Alina and Arseniy helped us with this)
With the help of decorative buttons and strong threads, cones were attached to the Christmas tree.
Now we look forward to the rain when the scales close showing that air humidity has increased.
A pine cone is a unique phenomenon in nature, it only needs to be learned how to use it. I hope that as a result of observing the cones, children will understand why they open and close.
Children must come to the conclusion that the cone is nature's weather forecaster.
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For this you will need:
- human hair;
- gasoline or acetone;
- hot glue;
- nitro glue;
- nails;
- carpentry and locksmith tools;
- drawing accessories;
- a sheet of plywood 5 mm thick;
- thick paper;
- steel wire;
- a rod from a ballpoint pen;
- a roller with an inner diameter of about 1 cm.
In the hygrometer, you can use not only hair, but also high-quality cotton thread.
Making a hygrometer
Take a human hair at least 40 centimeters long. The hair should not be dyed and in no case varnished. First of all, it must be degreased. To do this, wash your hair in water with washing powder (without conditioner) or boil it in a soda solution. You can also apply a rinse in gasoline or acetone. Attach a small plumb line to one end of the hair. It is best if the plumb line has a point. You can use the sharp end of a nail or the solvent-washed tip of a ballpoint pen to make a plumb line. It is important that the weight of the tip is sufficient to straighten the vertically hanging hair. To fix the plumb line on the hair, use hot glue or a drop of nitro glue. Pick up a small nail, put on it a piece of a ballpoint pen about 5 mm long or any other suitable plastic tube. It is important that the tube is free to rotate and not slip through the cap. The hygrometer is mounted on a vertical board or plywood panel with a horizontal base. Drive in the nail you prepared with a plastic tube in the center of the vertical panel so that the hair thrown over it with the free end can be attached to the horizontal base. The part of the hair thrown over the nail was about a third of its total length. Throw the hair over the nail and secure the free end with hot glue. When the humidity changes, the length of the hair will change, and the tip of the plumb line will rise and fall. Equip the hygrometer with a scale. It can be made from a strip of paper pasted on the dashboard behind the plumb line.Hygrometer calibration
You can calibrate the hygrometer in the following way: bring the device into the bathroom, after turning on the hot shower in it. When the room begins to fill with steam, mark on the scale the lowest point against which the tip of the plumb line will stop as 100%. Next, place the appliance in a heated and cooling stove oven (not very hot so as not to burn the appliance). At the top point opposite the tip, put a mark of 0%. The 50% mark can be placed in the middle between the two extreme marks. You can carry out a more accurate calibration using a control hygrometer, but you can also calculate it, since the scale of a hair hygrometer is linear. If you could not get a long hair and the sensitivity of the device is not enough, equip the hygrometer with an arrow. Put a small pulley on the nail instead of the plastic tube. As a pulley, a roller from a curtain rod, a wheel from a toy car with a tire removed, you can also make it yourself. The main thing is that its diameter does not exceed 1 cm. In this case, the hair must be wrapped around the roller for one turn. Make the arrow out of a light material: elastic wire or a strip of plastic. Glue the arrow with hot glue to the end of the roller so as not to interfere with its rotation on the awn. In this case, the hygrometer scale must be made in the form of an arc or a sector of a circle.You can, of course, buy a thermometer-hygrometer, but it is interesting and cheaper to make it yourself. In view of the excess of free temperature sensors and some other parts lying around idle, I decided to assemble this device that I need in everyday life on ATmega168V and SHT21. Read more on…
In the circuit, the sensor measures not only temperature, but also humidity. For me, the practical use of this feature is doubtful, but since it might come in handy for someone, I decided to use it as well. By the way, this is probably one of my longest projects (software was written for a month!). The development was delayed mainly due to lack of free time and the buggy of some compiler, from some company, but first things first…
The thermometer does not have any exotic features - it just shows the temperature with humidity and a battery charge indicator. The display of data takes place on the screen from the Siemens phone. I wrote about how to connect it to the microcontroller earlier (link at the end of the article). I chose this display as the most economical display I have and it is very thin and easy to control with a microcontroller. The only drawback: at a voltage below 2 volts, nothing can be disassembled on it (although the controller works stably even at 1.8 V). That is why when the battery is discharged to about 2 volts, the battery indicator will be displayed on the screen.
I took the time to draw (or rather copy!) Big beautiful numbers to display the temperature and small strict numbers to display the humidity. What came out of it is clearly visible in the pictures.
Printed circuit board? No, have not heard:-). Yes, and why is she here if the details are one, two, and miscalculated. Good installation + high-quality case and nothing is scary for this device. Moreover, I do not plan to play football with them. All parts are connected with MGTF f-0.07 mm wire - the best mounting wire in the world :). Only it is difficult to clean it, but this is just its only minus. I don’t have any battery holder (due to the 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 a relatively low temperature of the soldering iron, and I didn’t dare to overheat the battery. All exposed contacts were carefully insulated with tape before shoving the whole thing into the case. I bit off the extra legs of the controller (with the exception of those that are needed for the firmware), and the case itself was glued with superglue. The display, by the way, also rests on it. As a result, the device looks much more beautiful from the outside than from the inside 🙂 It is also important not to forget to make a hole in the case for the sensor if we want to measure the temperature not inside the device case. The case itself is called G1906 (~$2), and this is how it looked at the very beginning of my mockery of it:
The most difficult thing here is to do just such a rectangular hole. I did this: first drawing a rectangle and then making holes along the contour with an ordinary drill with which I drill boards. After drilling 100500 holes, the rectangle breaks out, and the edges are cleaned with a file. By the way, this is perhaps the most even hole of all that I have ever done 🙂
Everything is quite simple and trite, except for a small highlight of power management. I spied it in some magazine: We close the button, the device starts, sets a logical unit 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 of the entire device. Everything is ingenious and simple. Before use, you need to twist the resistor R4 so that at three volts of supply voltage, a voltage of 1.1 volts is present 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 for a long time.
And now we got to the most interesting part of the project: the software. Taking this opportunity, I would like to pour tons of hatred on the creators of the micropascal compiler. I have never seen such curvature. After my program began to occupy more than ~ 10kb of flash memory, inexplicable glitches began, which I skillfully overcame by stuffing various crutches. In my program, you can find unnecessary UART initialization (it doesn’t work without it), port settings through assembler inserts, and some other interesting things! I no longer write in micropascal, which is what I wish you.
Ready-made thermometers and thermometer-hygrometers can be bought, for example, here:
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Recently, an old friend came to 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. The best solution seemed to be to simply notify the owner with a call to the mobile phone when one of the motion sensors is triggered.
The most common and simple device for measuring temperature and humidity in the process of drying wood in drying chambers is an electronic psychrometer.
Principle of operation and brief description: The psychrometer consists of two thermometers: "dry" and "wet". "Dry" is just a thermometer, and "wet" is put on a cotton wick, 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 higher the evaporation rate, and hence the psychrometric difference. Thus, the "dry" thermometer shows the temperature of the air 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 rate. 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 simply set the temperature and psychrometric difference in the drying mode.
How to make a psychrometer
Option 1. An easy-to-make electronic psychrometer with a water supply system, made according to the principle of an automatic drinker, is shown in the upper 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 designed for gaseous use only, water from the wick may seep 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 wall of the chamber with the help of a corner. For a "wet" thermometer, a stainless steel bath is made. You can use (if you have one) a ready-made bath made of heat-resistant plastic, aluminum, or another material that is resistant to corrosion. It is not recommended to make a bath from "ferrous" metal, as it will quickly rust, rust will "clog" the wick and the psychrometer will start to give incorrect readings of the psychrometric difference.
Do not make an unnecessarily wide or long bath. This will lead to an increase in evaporation from the surface of the water in the bath and you will have to add water more often, but you do not need it. If you find a ready-made bath, but it is too large, then make a lid for it with a slot for the wick.
"Wet" thermometer is installed at a height of 2-3 centimeters from the surface of the water in the tub. This height should not be made too high, as this will impair the wettability of the wick and the psychrometer will give incorrect readings.
The tank for pouring water into the bath is made from an ordinary aluminum canister. Do not use canisters made of polyethylene and other plastics with a low melting point. 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.
The entire manufacture of the tank comes down to drilling a hole in the lid of the canister and installing a fitting on the lid (which is also bought at a hardware store). When installing the fitting, it is recommended to smear 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 does it work. 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 stops. It's simple: the canister is airtight, water is poured out until the space vacated in the canister is occupied by air entering through the hose. As soon as the flow of air stops, the outflow of water also stops. In the future, due to evaporation, the water level in the bath will decrease, the hose opening 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 the wood, a lot of water will evaporate from the bath. From our experience, 10 liters of water is enough 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 the entire drying, so you have to stop drying, open the drying chamber and pour water into the canister. By itself, this is not convenient and not desirable, and if the psychrometer is also located in a hard-to-reach place...
So if:
- The drying chamber is located in a heated room.
- There is a heated room next to the camera.
- The psychrometer is installed in a hard-to-reach place.
Option 2 (middle and bottom photos). Everything is similar to option one, just another bath is added. This bath, together with the canister, is placed in an easily accessible place in the chamber (for example, near the technological door) or in a warm room outside the chamber. The bath of the tank (in the middle photo) and the bath of the psychrometer (in the bottom photo) are installed at the same level and are connected to each other by 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, you will need to buy not one, but three fittings and more hoses. But ease of use will quickly outweigh the costs.
The main mistake with this option is that if the hose is not laid correctly, it “airs up” and water from the tank bath stops flowing into the psychrometer bath. The rule for laying the hose is simple: only one slack is allowed. If there are at least two of them, then an air lock 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 drying, at any time you can check the remaining water in the canister.
Water. Distilled water is recommended to power the psychrometer. When drying hardwood species with a long drying time, this condition is mandatory. When drying easy-drying rocks, some deviations are possible. If tap water is soft, then you can use it, but after each drying it is necessary to rinse the wick in running water. If the water is hard, softened water can be used. There are water softeners at any large boiler house, you can take water from them. What to do if the water is hard and there is no other? Collect rainwater in summer, melt snow in winter. It's not hard.
Wick. The wick should be made only from natural cotton fabrics: chintz, cambric, batting, and so on. You can use ordinary gauze rolled up in four layers.
It is recommended to check the condition of the wick before each drying. A clogged (salted) 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 fix the wick on the thermometer, for example, with wire (see photos).
Location 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 chamber wall from the pressure side (from the side of the drying agent inlet to the lumber stack), at a height of about 1.5 meters, at the middle of the chamber length.
Special moisture meters are used. To date, there are needle, contact and chip modifications. In terms of parameters, they are quite different. However, there are not many manufacturers on the market for moisture meters. The main companies include EMSO and Valcom. There is an average good moisture meter on the market in the region of 1500 rubles.
How to do it yourself?
If necessary, you can make a moisture meter for wood with your own hands. Its circuit includes a dielcometric type sensor. Also, the device will require a compact generator. Its limiting frequency parameter must be no more than 30 MHz. Contacts for a home-made model are more expedient to select needle-shaped. Also, to make a moisture meter for wood with your own hands, you will need a three-channel type chip.
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 tubular type. The display is more expedient to select lowercase. Compared to text counterparts, it is simpler. Capacitive electrodes are used directly in moisture meters. In turn, the catcher will need to be installed resistive. Batteries are selected last for the model. In this case, you can use ordinary finger batteries.
contact models
Contact moisture meters for wood are well suited for working with plywood, as well as parquet. Additionally, in the construction industry, devices are used to determine the moisture content of panels. If we talk about contract features, then low-frequency generators are used in the devices. Directly the probes are installed tubular type.
The dielectric constant of most moisture meters does not exceed 3 F/m. The maximum temperature of this type of model is able to keep at 40 degrees. The display is used as a line and text type. Many modifications are equipped with temperature sensors. The calibration function is available on many devices. It costs an average of a high-quality moisture meter in the region of 2 thousand rubles.
Needle moisture meters
Needle moisture meters for wood are used, as a rule, for pine or spruce. The sensors in all configurations are of the dielectric type. If we talk about the parameters, then the measurement accuracy mainly fluctuates around 0.2%. The maximum humidity threshold of devices does not exceed 35%. The minimum allowable temperature for models is 0 degrees. Microprocessors in many devices are used with amplifiers. There is an average moisture meter for wood (needle) in the region of 1200 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. Directly traps are installed resistive type. The minimum moisture threshold for models does not exceed 5%. In turn, the devices are at level 1 PH. Displays are often used in moisture meters 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 AP
In the construction industry, the presented moisture meter is in great demand. It is ideal for working with parquets and panels. Also, this moisture meter is 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 the measurement of wood moisture is fast. The electrodes are capacitive type.
The maximum humidity threshold does not exceed 40%. In terms of dimensions, the specified moisture meter is very compact, and belongs to the class of portable devices. According to the documentation, its mass without batteries is 80 g. The resolution of the model is at the level of 1.3 pH. The maximum allowable temperature of the model is exactly 35 degrees. It is forbidden to use the presented device in frost. 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. According to customer reviews, the resolution of the device is quite high. Directly the generator of the model is used at 22 MHz. According to the documentation, the maximum allowable temperature is 40 degrees. The display in the device is of the text type.
Batteries are used for 1 mAh, so they last a long time. In this case, the manufacturer provides a catcher of a resistive type. If you believe the reviews of experts, then there are no problems with determining the importance of chips. The maximum measuring depth is 10 mm. The user can purchase the presented moisture meter for 1400 rubles.
Model "Valkom EM4806"
The specified 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 around 0.2%. The maximum allowable humidity threshold is 30%.
The catcher in the device is provided of a resistive type. The microcircuit is used three-channel, and the generator is set to low-frequency. According to the documentation for the device, the case is provided with the IP 62 protection system. The presented model weighs exactly 80 g. The moisture meter memory is enough for 30 thousand measurements. The user can buy it for 1500 rubles.
Reviews about "Valkom M804"
The specified wood moisture meter generally receives good reviews. The main advantage of the model lies in its compactness. If we talk about more constructive features, it is important to note that he uses probe contacts. There are two sensors directly in the case. Thus, the measurement accuracy is quite high.
The probe in the device is provided by the manufacturer as a tubular type. The resolution of the device fluctuates around 1.3 pH. The maximum moisture 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"
In construction safra, the presented moisture meter is in great demand. First of all, we should mention a high-quality generator, which is installed with a frequency of 33 MHz. In this case, the sensor is of a dielectric type. Contacts, in turn, are used needle-shaped. If you believe the reviews of experts, then the measurement accuracy of the model is high.
It can be used for parquet and panels. The minimum allowable temperature of the device is 0 degrees. The resolution index is 1 pH. The catcher itself in the device is of a resistive type. The microprocessor is used with a pulse amplifier. The maximum humidity threshold of the device is at around 40%. You can buy this moisture meter for only 1400 rubles.
Description "Extech MO280"
This portable moisture meter features a protected housing. The sensor he uses is of a low-frequency type. In turn, there are needle contacts. There is a calibration function in the presented instance. The ambient temperature can be determined using this device. 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 of the model is allowed at 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 the store for 1300 rubles.
Model "Extech MS60"
These wood moisture meters are often used by professional builders. They are able to work even at a temperature of 0 degrees. The body protection system of the model is of high quality. According to consumer reviews, the device is quite simple to use. Batteries for the model are selected with a capacity of 1.2 mAh.
According to many owners, they last for a long time. The probe of the presented moisture meter is of tubular type. The microcircuit in the case has a 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.
Do not operate the device at temperatures above 35 degrees. The maximum allowable humidity is 40%. These moisture meters on the market are sold at a price of 2 thousand rubles.
The level of humidity in the air of the environment can affect not only the well-being of a person, but also the condition of 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 microclimate in the room, special humidifiers or dehumidifiers are used, as well as air conditioners with automatic humidity control functions.
Use special instruments to measure:
- hygrometers;
- psychrometers.
A hygrometer is one of the measuring instruments, thanks to which you can determine the level of humidity.
Additional information: In 1783, the Swiss scientist Horace de Saussure designed the first hair hygrometer, but Leonardo da Vinci began working on the invention of this meter as early as 1400.
There are several types of hygrometers:
- hairline;
- weight;
- condensation;
- electronic;
- electrolytic;
- film;
- ceramic.
Each of the devices has a special principle of operation. For example, the design of a hair hygrometer is a system of U - shaped tubes. They are filled with a special substance that absorbs water vapor. Air is pumped through this system by means of a pump and its humidity is determined.
The most accurate meter is considered to be a condensation hygrometer. It measures the amount of condensation that forms on a glass surface after being exposed to sunlight. The error in the operation of such a device is very low.
A psychrometer is another of the environmental humidity meters.
Types of psychrometers:
- August psychrometer (station);
- Assmann psychrometer (aspiration);
- remote psychrometer.
The August psychrometer is one of the most well-known 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 wet or wetted. The end of this thermometer in the form of a cover is wrapped with a batiste cloth or gauze, the end of which is lowered into a reservoir of water located on the back of the psychrometer.
If the end of a wet bulb bulb is dipped into a tank, it will indicate the temperature of the water there, not the air that circulates above it. Therefore, it must be taken 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 cloth evaporates, causing the temperature on the wet bulb to drop until the thermometer shows the temperature at which the steam becomes saturated. At this point, the data displayed on the wet bulb will represent the actual ambient temperature.
Determination of 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 sunlight and extraneous thermal influences for 10-15 minutes, after which the measurement results of each of the device's thermometers are recorded.
The thermometer scale is divided from - 25˚ to + 50˚ into intervals of 0.2 degrees.
How to use the psychrometric table
To determine the level of humidity based on psychrometer data, a special psychometric table is needed. The first column of the table shows the dry bulb temperature in ˚C. In the first line - 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, the determination of air humidity with a psychrometer is much easier 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 velocity at the measurement site, the greater the difference in the final result of both thermometers of the psychrometer. This error was corrected in the aspiration-type psychrometer or, as it is also called, the Assmann psychrometer.
What is the peculiarity of the Assmann psychrometer?
The Assmann psychrometer is a much more complex and more reliable device for measuring air humidity. Both construction thermometers are located at the lower ends in a special metal case, which protects them from sunlight, thermal effects, and 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/s.
Determination of humidity using this psychrometer: the device is suspended at the place of study at a height of 1.5 m from the floor; results are obtained in 10-15 minutes in winter and 4-5 minutes in summer.
The August psychrometer and the Assmann psychrometer have in common that both contain glass-mercury thermometers. The disadvantage of these devices is their fragility and, accordingly, the inability to carry out measurements remotely.
What is the difference between a remote psychrometer and other devices
A remote psychrometer is another example of a humidity measuring device. The design of this measuring device uses electronic devices such as a resistance thermometer or thermistors.
The main types of remote psychrometers:
- manometric;
- electrical.
A manometric psychrometer consists of one or two manometric type thermometers. In electronic psychrometers, as in all other remote meters, silicon transistors are used, which replace the sensors of dry and wet bulbs.
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 function of the hygrometer is to measure not only the humidity of the air, but also the humidity of various solids.
The indicators of a psychrometer, despite the simplicity of its design, are always more reliable, which is why in the notes to the instructions of some hygrometers it is recommended to check the readings on a psychrometer.
How to find out air humidity without measuring instruments
To conduct this experiment, you will need an ordinary glass, some water and a refrigerator. A glass of cold water is placed in the refrigerator for several hours. When the temperature of the liquid in the vessel reaches 3 - 5 ° C, the glass is placed in a 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 to 10 minutes of observation. If the air in the room is very humid, then large drops of condensate form on the walls of the glass within 5 to 10 minutes. If none of the two previous options is observed, the air in the room is of medium humidity.
How to make a do-it-yourself air humidity meter
The psychrometer is a fairly simple invention in its design, so anyone can make it on their own.
Necessary materials:
- two alcohol thermometers;
- a small piece of batiste fabric;
- several wooden slats;
- small screws;
- glass jar.
To stand the psychrometer, you need to take a small wooden plate measuring 50 mm wide and 120 mm long. We attach a rail 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 thermometers will be held.
For compactness and highest accuracy of indicators, thermometers should not be placed at a great 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 body of the psychrometer is assembled, the lower bulb of one of the thermometers is wrapped with a batiste cloth. The end of the fabric is lowered into a vessel containing a non-freezing liquid.
When checking the indicators 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 of the finished product will receive a useful tool for measuring the level of air moisture.
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A hygrometer is a moisture meter for an incubator, with which you can control the humidity of the air inside the case. But in different periods of incubation, the humidity indicators should differ: in the first week - 65-75%, in the second - 40-50%, in the third - 75% (data for hatching chickens are 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 the hygrometer for the incubator into the container through a special hole. It is fixed for 5-10 minutes in limbo.
After the specified time, the humidity readings should appear on the display of the moisture meter. In the case of opening the incubator lid to lower the device, you need to wait about an hour to get accurate data.
For long and productive operation of the device, it is protected from falls and bumps, do not pull the wire to which the sensor is connected.
In order for the device to function normally, it is necessary to observe the temperature regime (from -40 to +70 degrees). You should also reduce the likelihood of dust, dirt and various liquids entering the device.
The humidity sensor for the incubator works according to a certain algorithm:
- If the humidity level inside the container has changed, which was set by the poultry farmer, the equipment works and signals possible problems.
- After that, the farmer must study the moisture indicator, add or remove the amount of water in the incubator.
- After a few hours, check the sensor readings again. You need to monitor it constantly so that the chamber has a stable level of humidity.
Types of hygrometers for an incubator
There are different types of hygrometers, which have their own characteristics, individual type of work, advantages and disadvantages.
There are the following varieties:
- Weight hygrometer for an incubator. It consists of several combined tubes, which contain a hygroscopic substance that absorbs moisture. With the help of this system, some air is drawn in and its humidity is determined.
- Hair moisture meter. It is known that hair changes length with changes in air humidity. Due to this, it is possible to measure relative humidity - from 30% to 100%. The hair is stretched on a metal frame, and if the humidity indicator changes, the data is transmitted to the arrow, which moves along the scale.
- Film air humidity sensor for incubator. Equipped with a special organic film element. When the humidity rises, it expands, and when it decreases, it contracts.
- 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 take the simplest device. But for incubators with 100 or more eggs, it is recommended to buy more powerful hygrometers.
Typically, hygrometer readings are wrong by about 5%. If you need a more accurate device, then optical views should be preferred. In order for the equipment to serve for more years, when buying it, you need to look at the level of its protection.
Measured on the IP scale. The higher the value, the more resistant the instrument is to dust, dirt and water.
Hygrometer Models
| Instrument name | Price | Advantages | disadvantages |
| MAX-MIN | 600 rubles | Equipped with a thermometer and an alarm clock. An additional sensor can be connected. | There are no disadvantages. |
| Digital moisture meter with remote sensor. | 250 rubles | Humidity measures from 10 to 99%. Battery LR44 included. Using the device, you can work remotely. | Too high measurement error - 7-8%. Moreover, the device quickly fails. |
| Stanley 0-77-030 | 6000 rubles | Has a shock-resistant housing, LCD display, has a small size. | High price. |
| HP-2GD | 600-700 rubles | Convenient interface, easy to use. Just press the button and select the desired option. | Poor quality of the body material. |
| Ryobi Phoneworks RPW-3000 | 2200 rubles | Combined with the work of a smartphone, data can be received directly on the phone screen. | There are no disadvantages. |
| DC-206 | 300 rubles | The model has a compact size, can be used in small incubators. | The case is easily deformed under mechanical influences. |
| HTC-2 | 600 rubles | It has a built-in thermometer and clock. | No. |
| TA308 | 700 rubles | 3 in one: humidity sensor, clock and thermometer. | High error of indicators: above 5%. |
If you are wondering which is the best of all options, then this title is occupied by the MAX-MIN device (3 in one). It's not just a humidity sensor. In the plastic case there is a thermometer for the incubator, which shows the temperature as accurately as possible. The device is also equipped with an alarm clock.
In addition, an optional MAX-MIN TH218A humidity sensor can be connected to it. By placing it right inside the case, you can not be afraid of violating 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, which will allow the poultry farmer to quickly learn 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 must either be replaced or properly adjusted.
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 hours). All indicators are visible from afar, highlighted in bright colors. Therefore, you do not have to approach the incubator every time, because the data on its work can be viewed from a distance. Particularly pleased with the cost of the device - only 600 rubles.
How to make a hygrometer with your own hands
And although the hygrometer for the incubator is inexpensive, you can make it yourself. A do-it-yourself moisture meter for an incubator gives more accurate indicators than its counterparts purchased in a store.
To make a homemade device, you must:
- Take two mercury thermometers to measure air temperature, water. It is also necessary to take a board on which both thermometers will fit.
- Both thermometers must 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 with a cloth, without contact with it. Then the fabric should be tied with a thread, not too tight. This thermometer is called wet, and the second is called dry.
- The edge of the fabric should be lowered into the water by 5-7 mm.
- The indicators of both thermometers are compared with each other and, using the table, they find out the relative humidity in the incubator.
Sometimes you have to spray the eggs with water to increase the humidity in the chamber. But to resort to this technique should only be in the case of eggs of waterfowl. For the rest of the embryos, a moisture content of 50-60% is sufficient. You can calculate the moisture index using the table below.
| Dry thermometer data | Temperature difference in degrees | |||||||||
| 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | |
| Relative humidity in percent | ||||||||||
| 15 | 100 | 92 | 80 | 71 | 61 | 52 | 44 | 36 | 27 | 20 |
| 16 | 100 | 90 | 81 | 71 | 62 | 54 | 45 | 37 | 30 | 22 |
| 17 | 100 | 92 | 81 | 72 | 64 | 55 | 47 | 39 | 32 | 24 |
| 18 | 100 | 91 | 82 | 73 | 65 | 56 | 49 | 41 | 34 | 27 |
| 19 | 100 | 91 | 82 | 74 | 65 | 58 | 50 | 43 | 35 | 29 |
| 20 | 100 | 91 | 83 | 74 | 66 | 59 | 51 | 44 | 37 | 30 |
| 21 | 100 | 91 | 83 | 75 | 67 | 60 | 52 | 46 | 39 | 32 |
| 22 | 100 | 92 | 83 | 76 | 68 | 61 | 54 | 47 | 40 | 34 |
| 23 | 100 | 92 | 84 | 76 | 69 | 61 | 55 | 48 | 42 | 36 |
| 24 | 100 | 92 | 84 | 77 | 69 | 62 | 56 | 49 | 43 | 37 |
| 25 | 100 | 92 | 84 | 77 | 70 | 63 | 57 | 50 | 44 | 38 |
Ministry of Education of the Krasnoyarsk Territory
Regional State Autonomous Professional
educational institution
"Krasnoyarsk College of Transport and Service"
project theme:
"Hair hygrometer model"
Done: students
groups MP1-17 Pogodaev M.A. Gorensky S.A. Checked by: physics teacher: Levdikova E.D.
Krasnoyarsk 2018
Content.
Introduction………………………………………………………….3 p.
Section 1. Theoretical part…………………….……………4 p.
Instruments measuring air humidity………………4 p.
Alternative ways to measure air humidity……………………………………………………..6 p.
The history of the emergence and development of the hygrometer…………7p.
Section 2. Practical part……………………………….……9p.
The device and principle of operation of the hair hygrometer…………………………………………………….8 p.
Scheme of a hair hygrometer……………………………..9 p.
Description of the assembly of the hair hygrometer model………10 p.
Comparison of the results of readings of an electronic hygrometer, a psychrometer and a hair hygrometer.………...……… 10 pages.
Section 3. Final part………………………………………………………………………………………………………………………….
3.1. Conclusion ……………………………………………….….13p.
Applications………………………………………………….……14 p.
References……………………………………………… 15 p.
INTRODUCTION
Moisture enters the body of animals and humans mainly with food or drink. However, a sufficient amount of it is necessary not only for internal organs, but also for the mucous membranes of the eyes, respiratory tract, and skin. Therefore, it is important not only to take the liquid inward, but also to obtain it from the surrounding moist air. To determine the humidity index and maintain it at a normal level, special measuring instruments are used.Among the most common special devices, psychrometers and hygrometers should be distinguished. Such devices serve a single purpose, but their work is based on fundamentally different principles. We were interested in the device hair hygrometer. Having studied its more detailed device, we realized that it can be made by hand.
Relevance our project is that to study the topic of air humidity, a model of a hygrometer device is required.
Objective of the project: assemble a working model hair hygrometer.
Project objectives:
To study the devices and principles of operation of devices that measure air humidity.
Build a model hair hygrometer.
Compare measurements of a hair hygrometer with a psychrometer and an electronic high-precision hygrometer for a month, in the same class.
SECTION 1. THEORETICAL PART.
INSTRUMENTS MEASURING AIR HUMIDITY.
The psychrometric method for calculating humidity indicators has become quite widespread in everyday life. If a hygrometric device for measuring air humidity usually shows deviations in the indicators of the order of 5% in both directions, then in the case of psychrometers there are no such errors. The simplest psychrometers have two sensors - dry and wet. While the evaporation of water cools the wet sensor, the dry element of the psychrometer detects changes in ambient temperature. The result of measurements based on this principle is the formation of the necessary indicators in a special microprocessor device. Thus, it is easy to understand that a psychrometer is a device for determining air humidity, where the main role is played by the registration of indicators of the temperature difference on dry and wet sensors.
Fig. 1. Psychrometer.
A hygrometer is a device for measuring air humidity, the principle of which allows you to identify how a change in humidity indicators affects individual bodies and matters. A striking example is the hair hygrometer, where defatted human hair acts as a measurement tool. By changing its own length, based on changes in moisture indicators, the hair allows you to obtain data on the required indicator in the range from 30 to 100%.
Fig.2. Hygrometer.
1.2. ALTERNOTIVE METHODS FOR MEASURING AIR HUMIDITY.
MEASUREMENT OF AIR HUMIDITY WITHOUT APPLICATION OF EQUIPMENT.
There is a fairly simple way by which you can get fairly objective data on the level of humidity in the room. And for this, it is enough just to have an ordinary glass glass with water. To measure humidity, fill a glass with cold water. Then place the container in the refrigerator for several hours until the water cools down to a temperature of about 5. Having placed the glass in the room in which you want to know the humidity level, you should observe the surface of the glass, paying attention to the following: if the walls of the glass first fog up, and then dried quickly for several minutes, in which case the air in the room is dry; the preservation of the effect of fogging of the walls after 5-10 minutes after the start of observations indicates the average humidity of the air; the appearance of flowing streams on the walls of the glass indicates high humidity.
HUMIDITY MEASUREMENT WITH A THERMOMETER. A fairly effective device for measuring air humidity is a conventional thermometer. The use of a thermometer for this purpose is a kind of copying of the principle of operation of psychrometers. To begin with, using a standard mercury thermometer, the air temperature in the room is recorded, and then its head is tightly wrapped with wet gauze or a piece of wet cotton wool. After 10 minutes, new temperature readings are noted. To obtain humidity percentage, the wet bulb temperature is subtracted from the dry bulb temperature.
1.3. HISTORY OF THE ORIGIN AND DEVELOPMENT OF THE HYGROMETER.
Cardinal Nicholas da Cuza (1401-1464) was the first to develop an instrument for measuring humidity. He encountered this problem in the wool trade, as the value of wool depended on its weight. Wool buyers quickly figured out that the same quantity could be sold at a higher price during rainy days. Therefore, sellers waited for rains, and buyers for dry days. To determine fair value, Cardinal Nicolás de Cuza invented the first instrument for determining moisture content. He used scales, placing more wool on one bowl, and on the other stones equal in weight to the wool. At each sale, he put so many additional stones on the scale that the balance was maintained. Then, the amount of liquid in the wool was determined by the number of additional stones. After that, buyers and sellers could begin to negotiate the price of wool.
The German mathematician Johann Heinrich Lambert (1728-1777) proposed to call any device that measures humidity a hydrometer (later it was renamed a hygrometer). In 1774 Lambert invented a mechanism in which he used natural leather as a measuring element. Johann Lambert was also the first to deduce the relationship between temperature and humidity (relative humidity).
Decaussure (1740-1799) invented the hair hygrometer in 1783. These measuring instruments use human hair, otherwise light hair was considered more suitable for this. The natural composition of human hair leads to an error in measurement of only 2.5%, so industrial hair hygrometers have an error of 2.5%.
Relative humidity measures the amount of vapor in the air, which is expressed as a percentage of the maximum vapor that can be contained in the air at the current temperature. Here the temperature has a high humidity, for example, if the hygrometer shows 50% humidity at a temperature of 30 ° C, and then the temperature drops, then the relative humidity will increase
Thus, the colder the air, the less moisture it can hold.
SECTION 2. PRACTICAL PART.
2.1 . DEVICE AND PRINCIPLES OF OPERATION OF THE HAIR HYGROMETER.
The hygrometer allows you to determine the relative humidity of the environment, which is one of the most important components of the microclimate of the room. The moisture content in the air affects people's well-being. This indicator must be within the average range. Reduced air humidity can lead to difficulty breathing and drying of the mucous membranes, and high humidity can lead to a deterioration in physical condition. It is especially necessary to strictly monitor this value for people with respiratory diseases. The principle of operation of a hair hygrometer is based on the property of a fat-free human hair to change its length with a change in air humidity. With a decrease or increase in air humidity, the length of the hair changes. Under the influence of this change, the pulley turns and the end of the arrow moves along the scale, indicating the relative humidity of the air. Rules for using the device. During the demonstration, the hygrometer is mounted vertically in the foot of the universal tripod or hung on the wall. The device must be at eye level of the person working with it. The place where the hygrometer is to be installed must be free from vibrations, sources of heat or cold. A person working with a hygrometer should be at a distance of normal visibility of the scale marks from it and beware of breathing on it during readings. Check the position of the arrow. If the arrow is offset from "0", then use the adjusting screw to set it to "0".
Relative humidity is measured on a percentage scale. The scale division value corresponds to 1%.
When taking readings, the eyes of the worker must be on
level of the vertical tangent to the arrow so that the scale mark at the reference point is visible straight.
2.2. SCHEME OF THE HAIR HYGROMETER.
Fig. 3. Hair hygrometer model.
2.3. DESCRIPTIONS OF ASSEMBLY MODEL HAIR HYGROMETER.
To assemble the installation, we needed the following parts:
Threaded studs - 2 pcs.
Connecting plates - 3 pcs.
Mounting corners - 2 pcs.
Nuts - 11 pcs.
Bolts - 4 pcs.
Measuring scale with an arrow.
Fat-free hair - 7 pcs.
We assembled the model according to the scheme of Figure 3.
The arrow is in position 90, this is the initial position of the device.
The maximum deviation angle is 90, which means that one division of the scale will correspond to 1.1% humidity.
X\u003d 1.1%, it is not difficult to calculate how many divisions the arrow moved during the day.
RESULTS OF INDICATIONS OF ELECTRONIC HYGROMETER, PSYCHROMETER AND HAIR HYGROMETER.
To compare the results of the indications of the hair hygrometer model, we made comparisons with other devices that measure air humidity: a psychrometer and an electronic high-precision hygrometer.
The psychrometer is the difference between two thermometers: one measures the air temperature in the room, the other is placed in wet gauze, using a psychrometric table, we determined the air humidity in the classroom.
We measured humidity with these devices for a month, entered the results into a table and built a graph.
Textbook Physics Grade 10 G.Ya. Myakishev, B.B. Bukhovtsev, N.N. Sotsky (2010)