The first meteorological instruments. Meteorological instruments
Nastich Nadezhda Valentinovna
Thermometer
Thermometer is a device for measuring the temperature of air, soil, water, and so on. There are several types of thermometers:
-
infrared.
liquid;
mechanical;
electronic;
optical;
Psychrometer
A psychrometer is a device for measuring air humidity and temperature. The simplest psychrometer consists of two alcohol thermometers. One thermometer is dry, and the second has a humidification device. The alcohol flask of a wet thermometer is wrapped in cambric tape, the end of which is in a vessel with water. Due to the evaporation of moisture, the moistened thermometer cools.
Barometer
Barometer is a device for measuring atmospheric pressure. The mercury barometer was invented by the Italian mathematician and physicist Evangelista Torricelli in 1644; it was a plate with mercury poured into it and a test tube (flask) placed with the hole down. When atmospheric pressure increased, the mercury in the test tube rose, and when it decreased, the mercury fell.
Usually used in everyday life mechanical barometers. There is no liquid in the aneroid. Translated from Greek, “aneroid” means “without water.” It shows the atmospheric pressure acting on the corrugated thin-walled metal box, in which a vacuum is created.
Anemometer
Anemometer, wind meter - a device for measuring the speed of movement of gases and air in systems, for example, ventilation. In meteorology it is used to measure wind speed.
Based on the principle of operation, mechanical anemometers, thermal anemometers, and ultrasonic anemometers are distinguished.
The most common type of anemometer is the cup anemometer. Invented by Dr John Thomas Romney Robinson, who worked at the Armagh Observatory, in 1846. It consists of four hemispherical cups, symmetrically mounted on the cross-shaped spokes of a rotor rotating on a vertical axis.
Wind from any direction rotates the rotor at a speed proportional to the wind speed.
Precipitation gauge
A precipitation gauge, rain gauge, pluviometer or pluviograph is a device for measuring atmospheric liquid and solid precipitation.
The device of the Tretyakov precipitation gauge
The precipitation gauge set consists of two metal vessels for collecting and storing precipitation, one lid for them, a tagan for installing precipitation vessels, wind protection and two measuring cups.
Pluviograph
A device designed for continuous recording of the amount and intensity of liquid precipitation with reference to time (beginning of precipitation, end, etc.), and on modern weather vanes - using an electronic device.
The weather vane often serves decorative element- for home decoration. The weather vane can also be used for protection chimney from suffocation.
Meteorological instruments - instruments and installations for measuring and recording the values of meteorological elements. To compare the results of measurements made at different weather stations, meteorological instruments are made of the same type and installed so that their readings do not depend on random local conditions. meteorological elements
Meteorological instruments are designed to operate in natural conditions in any climatic zones. Therefore, they must work flawlessly, maintaining stable readings in a wide range of temperatures, high humidity, precipitation, and should not be afraid of large wind loads and dust.
Meteorological elements, characteristics of the state of the atmosphere: temperature, pressure and humidity, wind speed and direction, cloudiness, precipitation, visibility (transparency of the atmosphere), as well as soil and water surface temperature, solar radiation, long-wave radiation of the Earth and the atmosphere. Meteorological elements also include various weather phenomena: thunderstorms, snowstorms, etc. Changes in Meteorological elements are the result of atmospheric processes and determine the weather and climate.
Thermometer From the Greek Therme - heat + Metreo - measure Thermometer - a device for measuring the temperature of air, soil, water, etc. during thermal contact between the measured object and sensitive element thermometer. Thermometers are used in meteorology, hydrology and other sciences and industries. At weather stations where temperature measurements are carried out at certain times, a maximum thermometer (mercury) is used to record maximum temperatures between observation periods; the lowest temperature between periods is recorded by a minimum thermometer (alcohol).
Precipitation gauge Rain gauge; Pluviometer Precipitation gauge is a device for collecting and measuring the amount of precipitation. The precipitation gauge is a cylindrical bucket of a strictly defined cross-section, installed at the weather site. The amount of precipitation is determined by pouring the precipitation that fell into the bucket into a special rain gauge glass, the cross-sectional area of which is also known. Solid precipitation (snow, pellets, hail) is preliminarily melted. The design of the rain gauge provides protection from rapid evaporation of precipitation and from blowing out snow that gets into the rain gauge bucket.
Heliograph From Greek. Helios - Sun + Grapho - writing Heliograph - a recorder device that records the duration of sunshine. The main part of the device is a crystal ball with a diameter of about 90 mm, which works as a converging lens when illuminated from any side, and focal length in all directions the same. At the focal length, parallel to the surface of the ball, there is a cardboard tape with divisions. The sun, moving across the sky during the day, burns a stripe in this ribbon. During those hours when the Sun is covered by clouds, there is no burn-through. The time when the Sun was shining and when it was hidden is read by the divisions on the tape.
Ceilometer A ceilometer is a device for determining the height of the lower and upper boundaries of clouds, raised on a balloon. The action of the ceilometer is based: - either on a change in the resistance of the photocell, which reacts to changes in illumination when entering and leaving the clouds; - or on the change in the resistance of a conductor with a hygroscopic coating when cloud drops hit its surface.
Anemometer From the Greek Anemos - wind + Metreo - I measure Anemometer is a device for measuring wind speed and gas flows by the number of revolutions of a turntable rotating under the influence of the wind. There are anemometers different types: manual and permanently attached to masts, etc. A distinction is made between recording anemometers (anemographs).
Radiosonde A radiosonde is a device for meteorological research in the atmosphere up to an altitude of km. The radiosonde rises on a free-flying hot-air balloon and automatically transmits radio signals to the ground corresponding to the values of pressure, temperature, and humidity. At high altitudes, the balloon bursts, and the instruments are parachuted and can be used again.
Meteorological rocket A meteorological rocket is a rocket vehicle launched into the atmosphere to study it upper layers, mainly the mesosphere and ionosphere. The instruments study atmospheric pressure, the Earth's magnetic field, cosmic radiation, spectra of solar and terrestrial radiation, air composition, etc. Instrument readings are transmitted in the form of radio signals.
Meteorological satellite A meteorological satellite is an artificial Earth satellite that records and transmits various meteorological data to Earth. The meteorological satellite is designed to monitor the distribution of cloud, snow and ice cover, measure thermal radiation from the earth's surface and atmosphere and reflected solar radiation in order to obtain meteorological data for weather forecasting.
The main occupation of most meteorologists is not weather prediction, as is usually thought, but weather observation. Without observations there can be no forecasts. Moreover, in order to correctly make a weather forecast, you need to have the results of observations at tens and hundreds of points. Observations are carried out at meteorological stations.
A meteorological station (weather station) is an institution in which regular observations of the state of the atmosphere and atmospheric processes are carried out around the clock, including monitoring changes in individual meteorological elements (temperature, pressure, air humidity, wind speed and direction, cloudiness and precipitation, etc.). ). The station has a meteorological site where the main meteorological instruments are located, and a closed room for processing observations. Meteorological stations countries, regions, regions make up a meteorological network.
Only a few measurements can be carried out “by eye”; measuring instruments, their action is based on the laws of physics.
Often, having heard on the radio that the current temperature is such and such, we look at the outdoor thermometer outside the window and find a difference of up to three to four degrees. This is due to the fact that, firstly, the weather station from which we received information is located at some distance from our house; secondly, the instruments at the weather station are installed differently from ours; and thirdly, Appliances not nearly as accurate as meteorological ones. Observing the weather at a weather station is considered routine work because it is regulated by strict instructions that cannot be violated, otherwise observations made at different weather stations (and by different observers at the same one) cannot be compared. The point is not only that different stations should have instruments of the same design. The results of observations also depend on how and where these devices are installed, how to use them, how to record observations, etc. But the wealth of impressions that the object of observation—the weather—provides us with more than compensates for the apparent monotony of methods.
Each instrument at a weather station is equipped with a certificate, which indicates what corrections need to be made to its readings. For example, the thermometer certificate states:
from -5.7 to +2.1 +0.2
from +2.2 to +9.4 +0.1.
This means that if the thermometer shows -0.2°C, then the true temperature will be (-0.2°C) + (+0.2°C) = 0.0°C; if it shows +5.7°C, then the temperature is +5.8°C. For another thermometer, even if it was produced at the factory as part of the same series, the corrections will almost always be different. Such amendments are called instrumental. Any instruments have them, no matter what they measure.>
Now let's look at instruments designed to measure individual meteorological elements.
AIR PRESSURE
Air pressure is the most important meteorological indicator, even more important than temperature. Pressure is measured using a mercury barometer, which has not undergone significant changes in the three and a half centuries since it was invented by Evangelista Torricelli. Barometer allows you to determine altitude mercury with an accuracy of 0.1 mm. The pressure inside and outside is the same, so the device is hung on the wall in a closed room - the observation room, where observations are processed. A thermometer is built into the barometer scale, indicating temperature indoors, because as the temperature rises, the mercury in the barometer expands, and a temperature correction has to be entered into the readings using a special table.
In addition, a correction for absolute altitude is introduced into the pressure value, i.e. calculate the pressure that would be at a given point if the barometer were at sea level. Without this amendment, any Mountain country, within which they are located on different heights numerous weather stations, regardless of weather conditions would be shown on the isobar map as an area low pressure, and a very bizarre configuration.
In the observation room there is also an aneroid barometer, which is much more familiar to the general public; it is considered a less accurate instrument; it is kept just in case. The main part of the aneroid is a round tin box with grooved lids. The air has been pumped out of it and it is sealed. When increasing atmospheric pressure the lids bend inward, and when reduced, they straighten. The movements of the covers are transmitted to the arrow through a system of levers.
The action of the barograph located here, which draws a curve of changes in air pressure, is based on the same principle. An arrow with a tiny inkwell at the tip deflects up or down in accordance with the change in the total deflection of the lids of a stack of boxes and draws a curve of pressure change on the tape that is wrapped around the drum. The drum rotates using a clock mechanism. If the drum rotates per day, the curve is smooth; if for a week, the accuracy of the readings is less, but changes in pressure are more clearly visible. It is better to have both daily and weekly barographs. Other recorders rarely use weekly drums.
TEMPERATURE AND HUMIDITY
Temperature is the meteorological indicator we most feel; weather for us is primarily “warm” or “cold”. Air temperature is the temperature shown by a thermometer located at a height of 2 m above the ground and protected from direct sunlight. Thermometers are placed in one of the booths at the weather site. A weather site is a flat place about twenty meters from the weather station premises, with preserved natural cover (grass, moss, in a word, what constitutes the natural underlying surface for a given place). The booths are painted in White color, their walls are made of planks so that air passes into the booth freely, and the sun's rays never penetrate. There is a permanent ladder near the booth.
Two thermometers are urgent, i.e. show the current temperature. They are arranged vertically, the ball of which is wrapped in a strip of fabric, the end of which is lowered into a glass of water. Thermometers are respectively called dry and wet. Perhaps the reader has seen such a pair of thermometers in rooms where it is important to monitor air humidity, for example in museums. Mercury thermometers. But at very low temperatures mercury thermometers replaced with alcohol (mercury freezes at -39°). The temperature shown by the dry bulb thermometer is the current air temperature.
A pair of thermometers - dry and wet - make up a device called a psychrometer - a humidity meter. That is why the booth is called psychrometric. Evaporation of water requires heat, and a wet-bulb thermometer will typically read more low temperature than dry. If the air is dry, evaporation occurs quickly, a lot of heat is consumed and the difference in thermometer readings is large. At humid air The water evaporates slowly, and the difference in readings decreases accordingly. When the humidity reaches 100%, there is no evaporation, the thermometer readings are the same. Using special tables (and this is quite a substantial volume), the observer determines absolute humidity, relative humidity and humidity deficit, i.e. the amount of steam that the air can still hold. It is clear that at a relative humidity of 100% the moisture deficit is zero.
A person does not feel absolute humidity in the air, but notices relative humidity only when it differs greatly from the optimal one (60-70%) - either the air is too dry (40% or less) or too damp (90-100%). Dry air makes it much easier to tolerate frost and heat. Frost of 15-20° in the Murmansk region with one hundred percent humidity and even with a breeze (and the breeze sometimes knocks you off your feet) is much more severe than the famous Siberian frosts with low humidity and no wind.
Humidity is also recorded by another device - a hair hygrometer. Its action is based on the fact that, depending on humidity, degreased human hair - necessarily female (it is thinner) and light (the pigment impairs its sensitivity to moisture) - slightly changes its length.
The hygrometer is placed in the same booth as the psychrometer. Its readings are less accurate, they are checked using a psychrometer, but it allows you to determine humidity immediately, without calculations: its scale is calibrated in percentage relative humidity.
In the same booth there are two more horizontal thermometers - maximum and minimum. They are needed in order to know what the highest and lowest values the temperature reached during the observation period. The maximum thermometer is known to everyone - for example, a medical one. It shows body temperature not only when it is held under the arm, but also when it is taken out until it is shaken off. Only in the maximum thermometer used in meteorology, the temperature range is much greater, and the neck between the tube and the reservoir is wider, so it is easier to shake it off. That is why it is placed horizontally in the booth, so that the mercury itself does not accidentally slip into the tank. But it cannot be used as a medical device: no matter how much we hold it under our arm, it will show a temperature lower than normal, because it is long, and a significant part of the mercury takes on the temperature of the surrounding air. But what is it? The dry thermometer shows 15°, maximum 19°; To next term observations, the temperature is steadily falling, on the dry thermometer it is already 7°, and at the maximum it is again the same 19°! It turns out that the observer, having taken the readings of the maximum thermometer, forgot to shake it. It happened like that. To prevent this from happening again, a special column was introduced in the observation records: “Readings of the maximum thermometer after shaking.”
It is not difficult to guess that the minimum thermometer should show the lowest temperature during the observation period. The operating principle of this thermometer is as follows. A pin floats in a capillary containing colorless alcohol. At each observation period, slightly tilting the thermometer, adjust the pin to the surface of the alcohol and place the thermometer horizontally.
Meteorological thermometers allow you to take readings with an accuracy of 0.1°C.
In another booth, recorders are placed - a thermograph and a hygrograph, which continuously record changes in temperature and relative humidity; their clockwork drums are the same as those of a barograph, and the hands are connected to temperature and humidity sensors. Humidity sensor – human hair, temperature sensor – bimetallic plate.
To determine wind speed, there are many instruments of the most different designs. The essence of most of them comes down to one thing: the wind turns the turntable, and the revolution counter (mechanical or electrical) measures the speed of rotation. Such devices are called anemometers (translated from Greek as wind meter). Similar devices can now be seen in many cities: something like a large hollow melon, cut in half, is fixed on a vertical axis; the halves are offset relative to each other, on each half there is an advertisement for a company. The wind flows quite freely around the half, which has the convex side facing it, and exerts noticeable pressure on the concave side of the other half. And the whole device begins to rotate - the faster the stronger wind. it is not difficult to realize that the rotation will always be in one direction, no matter where the wind blows.
But for weather stations, the standard is not an anemometer, but a rather simple device, designed more than a hundred years ago by the director of the Main Geophysical Observatory in St. Petersburg G.I. Wild. Wild's weather vane consists of a weather vane - a metal flag that rotates freely on an axis, and a hanging metal board that rotates with the weather vane and is always located across the wind flow. Under the weather vane there are pins indicating the sides of the horizon - the main ones (north, east, south, west) - and intermediate ones - 8 in total. The wind direction is the side of the horizon from which the wind is blowing, so it will not be determined by the weather vane turned in the direction the wind is blowing, but and along the counterweight to it, always facing the wind. The stronger the wind, the more the metal board deviates from its vertical position. A metal arc with pins is welded next to the board, by which the degree of deflection of the board is determined, and then, according to the table, the wind speed. However, after working for a week or two, the observer writes the wind speed without looking at the table. The weather vane is placed at a height of about 10 m above the ground, on a separate standing pillar or above the roof of a weather station. Most often there are two weathervanes - with a light board for weak winds (up to 20 m/s) and a heavy one for strong winds (from 12-15 m/s). Here, however, a caveat is needed. Under the influence of a smooth, turbulent wind, the board will never assume a horizontal position. Swirls and turbulence of the flow can position the board horizontally, and even (for a certain period of time) lift it up. For example, if the direction is between west and southwest, and a light board is between the second and third pins, and when gusts reach the fourth, the record made at the time of observation looks like this: “WSW, l.d. 2-3(4)”. if the gloss is motionless, they write: “Quiet.”
Wind speed is measured in m/s; The exception is aviation and marine weather stations: the former give speed in km/h, the latter in knots (nautical miles per hour) to make it easier to compare wind speed with the speed of aircraft and ships, respectively.
It is easy to calculate that 1 m/s = 3.6 km/h = 1.94 knots (1 nautical mile = 1852 m). 15 m/s is a storm; 30 m/s is a hurricane, in which you can barely stand on your feet. The weather vane no longer reaches speeds of more than 40 m/s, we need special devices. One of them, a hurricane gauge designed for 60 m/s, also went off scale in the Khibiny region during individual gusts. And in Antarctica, about 90 m/s was once recorded. Judging by the destruction caused by tropical cyclones (typhoons), wind speeds in them can exceed 100 m/s.
SUN SHINE
During each observation period, sunshine should be noted. If the Sun is not covered by anything and shines brightly, a two is placed next to the Sun icon in the entry - the second degree. If the Sun is slightly clouded (this usually happens with high clouds), but objects cast shadows, the exponent is not given, i.e. the first degree is implied. When there are no shadows, but the position of the Sun in the sky can still be determined, a zero degree is written. If the Sun is covered by dense clouds or is below the horizon, the icon is not placed at all.
The heliograph device constantly records the sun's light. This is a unique measuring device that differs from all others in that it does not have a single moving part. Even a tape measure, even a tailor's centimeter, we must move and position so that the zero of the scale coincides with the beginning of the measured segment. The thermometer has a moving column of mercury; A thermograph or barograph has a clock mechanism that turns the drum and a hand that rises and falls.
The main part of the heliograph is a ball with a diameter of about 100 mm, made of good optical glass and well polished. Such a ball is a converging lens, which, unlike the usual lenses used in glasses, microscopes, binoculars, etc., does not have a single main optical axis: any straight line drawn through the center of the ball is its optical axis. Like any lens, the ball has its own focal length; it is the same in all directions. At this distance, a cardboard tape with divisions is placed along the surface of the ball in a special cage. The sun, making a visible movement across the sky, burns a trace in the ribbon. At some point, the Sun disappears behind the clouds and stops burning through the tape; it continues its movement behind the clouds, and when the sky clears, a new burn appears. Each large division on the tape corresponds to 1 hour. The tape lasts for 8 hours; after that, if the day lasts longer, they put a new tape and turn the clip 120° - this is exactly the arc the Sun describes in 8 hours. In winter, the days are short, one tape is installed - from 8 to 16 o'clock. In spring and autumn (and in the tropics - all year round) - two, from 4 to 12 and from 12 to 20 o'clock. In children, even at the latitude of Moscow, three tapes are already required, because the day lasts more than 16 hours, and even further to the north the Sun may not set, tapes are set at 0.8 , 16 o'clock
A heliograph can work as a recorder because it moves along with the rotating Earth, exposing first one point of its tape, then another, to the Sun for burning. The only thing comparable to them is a sundial - practically the same device, but not a self-recording one.
Clouds are one of the most difficult meteorological elements to observe, which is why there are no instruments. It is necessary to determine by eye the degree of cloud coverage of the sky (10% - 1 point of cloudiness, 30% - 3 points, the entire sky is covered with clouds - 10 points), the type and type of clouds, and at least approximately - their height. True, there are weather stations that launch a pilot balloon at each observation period, the rate of ascent of which is known; the ball disappeared into the clouds after so many seconds - and the altitude was known. But firstly, not all stations launch such balloons, secondly, the balloon can slip between cumulus clouds, and thirdly - and this is the most important thing - it is the last case that is considered lucky, because the pilot balloon is needed primarily for determining not the height of the clouds, but the direction of the wind at different heights.
There is, however, a rather primitive device called a nephoscope, which supposedly allows one to determine the direction and speed of movement of clouds, but I don’t remember a case where anyone used it...
The amount of precipitation is the thickness of the layer of water that would form from rain, snow, etc., if the water did not drain and evaporate. Measured in millimeters. The device (precipitation gauge) is simply a cylindrical bucket that is placed on a pole. At each observation period, the water accumulated in it is poured into a graduated cylinder, which makes it possible to measure the volume with an accuracy of 0.1 mm. If the precipitation is solid (snow, hail, graupel), the bucket is brought into the observation room, and when the precipitation melts, the water is poured into a glass. In summer, and especially in hot weather, the amount of precipitation must be measured immediately after rain, otherwise the water will evaporate.
Around the rain gauge bucket are located metal plates, forming something like a flower. They prevent precipitation (mainly, of course, snow) from blowing out of the bucket.
SOIL TEMPERATURE. SNOW COVER
The soil temperature is measured with the same thermometers as in the psychrometric booth, only all three are placed on the surface of the earth (in winter - on the snow) and are not protected from direct sunlight. In addition, agrometeorological stations measure soil temperature at different depths, usually 5, 10 and 15 cm. Thermometers are shaped like hockey stick: a reservoir of mercury is placed horizontally on required depth, and the scale protrudes above the surface. But corrections need to be made to the readings of these thermometers, because the protruding part of the body, in particular the mercury column, is influenced by air temperature and direct sunlight.
From the time permanent snow cover is established in the fall until it melts in the spring, the height of the snow cover is regularly recorded using a snow gauge.
METEOROLOGICAL PHENOMENA
We will mention them only briefly, because observations are carried out mainly without instruments and are of a qualitative nature; there are almost no measurements.
A meteorologist must constantly look out the window and leave the building more often, otherwise he may miss a lot. It started to rain - mark the time; The light rain turned into moderate rain - noticeable scurrying. You need to record the start and end times of precipitation, fog, blizzards, rainbows, aurora and much more. Each phenomenon has its own icon, so the entry resembles Chinese characters mixed with numbers.
Over the past decades, electronic devices have increasingly come into scientific and technical use. But traditional measuring instruments also retain their place; they usually serve as standards against which all other instruments are checked and adjusted.
Newspaper "Physics", No. 23’99.
To determine temperature under normal conditions, thermometers (mercury or alcohol) and thermographs (recording temperature changes over a certain time on a tape) are used.
Hygrometers, hygrographs and psychrometers are used to measure humidity. The most common are stationary August psychrometers and Assmann aspiration psychrometers. The operating principle is based on the difference in readings of dry and wet thermometers depending on the humidity of the surrounding air.
August's stationary psychrometer (Fig. 4.1, a) consists of two identical alcohol thermometers. The reservoir of one of them is wrapped in hygroscopic fabric, the end of which is lowered into a glass filled with distilled water. Moisture flows through the fabric to the reservoir of this thermometer to replace that which evaporates. Another thermometer (dry thermometer) shows the air temperature. Wet bulb readings depend on the amount of water vapor in the air. Having determined the temperature difference, the relative air humidity is found using the psychrometric table on the device body.
Rice. 4.1. Psychrometers:
a) stationary Augusta: 1 – thermometers with scales; 2 – base; 3 – fabric; 4 – feeder;
b) Assmann aspiration:
1 – metal tubes; 2 – thermometers; 3 – aspirator; 4 – wind fuse; 5 - pipette for wetting a wet thermometer.
The Assmann aspiration psychrometer (Fig. 4.1, b) is designed in a similar way. Its difference lies in the fact that to eliminate the influence of air mobility on the readings of a wet thermometer, a fan with a mechanical or electric drive is placed in the head part of the device.
Readings from thermometers are taken no earlier than after 3-4 minutes.
When working with an Assmann aspiration psychrometer, the value of absolute humidity depends on:
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Where 
- maximum humidity at wet bulb temperature 
(taken from Appendix 8); 
;
- temperatures shown by dry and wet thermometers, respectively, 0 C; 
- barometric pressure, mm Hg. Art.
Relative air humidity is determined by the following formula:
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Where 
- relative humidity, %; 
- maximum humidity value at dry bulb temperature 
(taken from Appendix 8).
In addition to formulas, the determination of relative humidity based on psychrometer readings can be made using a psychrometric chart or psychrometric table (Appendix 10).
The determination of relative humidity using a psychrometric chart is carried out as follows; the readings of the dry thermometer are marked along the vertical lines, the readings of the wet thermometer are marked along the inclined lines, and the readings of the wet thermometer are marked along the inclined lines; At the intersection of these lines, relative humidity values are obtained, expressed as a percentage. Lines corresponding to tens of percent are indicated on the chart by numbers: 20, 30, 40, 50, etc.
A hygrometer (Fig. 4.2) is used to directly determine the relative humidity of the air.
IN 
Its design is based on the ability of human hair (due to hygroscopicity) to lengthen in humid air and shorten in dry air.
Hygrographs are used to record changes in relative humidity over time on a tape. To determine the speed of air movement, impeller and cup anemometers are used.
Rice. 4.2 Hygrometer
TO
Rice. 4.3. Vane anemometer 1 – impeller; 2 – counting mechanism; 3 - arrester
A cup anemometer (Fig. 4.4) is used to measure air speed from 1 to 20 m/s.
IN
Rice. 4.4. Cup anemometer 1 – hundreds arrow; 2 – dial; 3 – arrow; 4 – four-cup pinwheel;
The mechanism is turned on and off by a lock 9, one end of which is located under a curved leaf spring, which is the bearing of the worm wheel. To turn on the counting mechanism, the lock 9 is turned clockwise.
The other end of the arrester raises the leaf spring, which, moving the wheel axis in the axial direction, disengages the worm wheel from engagement with the worm 6.
When the lock is turned against the arrow, the worm wheel engages with the worm and the anemometer wind receiver is connected to the gearbox.
The anemometer mechanism is mounted in a plastic housing, Bottom part The housing ends with a screw 10, which serves to fasten the anemometer to a stand or pole. In the anemometer body, on both sides of the arrester 9, lugs 8 are screwed in, through which a cord is passed to turn the anemometer raised on a stand (pole) on and off. The cord is tied to the eye of the arrester 9.
The wind receiver of the anemometer is protected by a cross made of wire arms, which also serves to secure the upper support of the wind receiver axis.
To determine the air speed measured using an anemometer (vane and cup), the formula is used:
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Where 
- speed of air movement, div./s; 
;
- respectively, the initial and final readings of the anemometer, div.; 
- measurement duration, s.
To convert the value of the movement speed dil./s to m/s, you should use the graphs for this anemometer (Appendix 11 a, b). To do this, a number corresponding to the number of divisions per second is found on the ordinate axis of the graph, a horizontal line is drawn from this point until it intersects with the graph line, and a vertical line is drawn down from the resulting point until it intersects with the abscissa axis. This point gives the desired speed of air flow, m/s.
To measure low air speeds (less than 0.5 m/s), thermal anemometers and catathermometers are used.
D 
To measure barometric pressure in this work, an aneroid barometer is used (Fig. 4.5). Atmospheric pressure measurement limits are from 600 to 800 mm Hg. Art. at temperatures from minus 10 to plus 40 0 C. Scale division value 0.5 mm Hg. Art.
Rice. 4.5. Aneroid barometer
Radiant thermal energy (thermal radiation intensity) is measured with an actinometer. In this device, the receiver of thermal energy is a screen made of dark and shiny aluminum plates, to which are attached microthermometers connected to a galvanometer. The electromotive force generated in thermopiles under the influence of thermal radiation is transferred to the galvanometer. Temperature values are recorded using galvanometer readings.