The barometer is an instrument for measuring atmospheric pressure. In hygienic studies, the most common metal barometers - aneroid and liquid mercury.
the aneroid barometerIn the barometer is the aneroid fluctuations of atmospheric pressure are perceived round metal box with wavy walls (aneroid box), which removed the air (Fig). Elastic walls of the box when the pressure SAG, when reducing the bulge. The transmission system walls of the box are connected with the arrow of the device. The latter indicates the scale of the device, graduated in millimeters of mercury, the amount of atmospheric pressure. Mercury barometer is a U-shaped bent glass tube, which is mercury; atmospheric pressure is determined by the difference between the levels of mercury in long and short sections of a tube.
For continuous monitoring of the changes of atmospheric pressure applied semusavebulia devices - barograph. Fluctuations of atmospheric pressure recorded on the tape that is placed on a rotating drum.
Measured atmospheric pressure usually in millimeters of mercury (mm RT. Art.) and millibar (mbar). 1 mbar = 0.75 mm RT. Art., 1 mm RT. Art. = 1,33 mbar.

Barometer (from the Greek. baros - the severity and metreo " measure") - an instrument for measuring atmospheric pressure. In the meteorological and hygiene practice, the most widespread mercury B. There are three systems of mercury b (Fig. 1): Cup (1), siphon (2) and siphon-plating (3).
Currently only apply Cup and siphon-Cup barometers. In stationary Cup b with compensated scale atmospheric pressure is determined directly by the position rtuti glass tube (on a scale marked on a metal frame B.). In the forwarding Cup B. before supervision of pre-special screw (at the bottom of the device) establish the level of mercury in the Cup at the zero point. In siphon-Cup barometric air pressure value measured by the difference of heights of mercury in long (sealed) and short (open) the knees. B. allows to produce samples with accuracy up to 0,Mr. Art. by means of the screw, which is based on leather bottom of a Cup B., the level of mercury in short (open) knee lead to a zero point, and then counts the testimony of the barometer. To determine tenths of a millimeter of mercury (in practice it happens rather seldom) is movable metal scale-Vernier. Found numeric expression atmospheric pressure is necessary by means of calculations on a special table to lead to 0 degrees. Temperature corrections to the indication of the Baltic can be substantial. B. establish away from sources of heat radiation (oven, heating devices, the sun), and the doors and Windows.
Very convenient for observation, especially in field conditions, metal barometer-aneroid (Fig. 2). It is less accurate than mercury barometer by which it usually verify. Metal Bourdon tube, bent in the form of a horseshoe, or more often metal pad with corrugated walls, from which you removed the air, changes its volume and deformed with pressure change. This deformation is passed through a system of levers arrow, which indicates the scale value of the atmospheric pressure.
At present the atmospheric pressure is more conventionally expressed in international units - millibars (MB). 1 MB is equal 0,75006 mm RT. senior and 1 mm RT. senior corresponds 1,3332 MB. For translation millimeters of mercury in millibars there are special tables.
Barograph - recording barometer for continuous record of atmospheric pressure. In hygienic practice used only aneroid barograph (Fig. 3). The principle of their action is based on deform under the influence of changes in air pressure package from 5-7 United together aneroid boxes; this deformation is transmitted by a system of levers Peru recorder. With increasing atmospheric; th pressure aneroid boxes are compressed and the lever with the pen is lifted up; in case of pressure drop box under the action you put inside it springs are expanding and the pen draws a line down. Write pressure plotted pen device on special graduated in millimeters of mercury or millibars to the paper, put on a rotating drum barograph. There are barograph with daily and weekly plant. To correct temperature influences on the testimony of barograph into them insert bimetallic capacitors. Barograph set away from heaters and protect from direct sunlight.

Fig. 1. System of mercury barometers. H - the height of the column of mercury, corresponding to the atmospheric pressure.
Fig. 2. The mechanism of barometer-aneroid (scheme): 1 - aneroid box; 2 - spring 3 - pin; 4 - crank; on - axis arrow; 6-shooter; 7 - hinged chain; 8 - coiled spring; 9 - scale.
Fig. 3. The mechanism of paragraph (scheme): 1 - lever recorder; 2 - column aneroid boxes; 3-5 - a system of drafts and levers.