you need
  • mercury barometer or aneroid.And if you need to continuously take readings of pressure, you should use the barograph.
mercury barometers, as a rule, shows the atmospheric pressure in millimeters of mercury.Just look at the scale of the level of mercury in the bulb - and now you know the air pressure in your area.Typically, this value is 760 ± 20 mm HgIf you want to know the pressure in Pascals, then use a simple system of translation: 1 mmHg= 133.3 Pa.For example, 760 mmHg133.3 * = 760 Pa =
101 308 Pa.This pressure is normal at sea level at 15 ° C.
take readings of the pressure on the scale barograph is also very simple.This device is based on the action of the diaphragm box that reacts to changes in air pressure.If the pressure is increased - the walls of the box bend inward if pressure drops - the walls are straightened.The whole system is connected with an arrow, and you just have to see what the atmospheric pressure arrow points on the scale of the instrument.Do not be alarmed if the scale is in units such as the HPA - a hectopascal: 1 hPa = 100 Pa.And for the transfer to the more familiar mmHgsimply use the equation from the previous item.
And find the atmospheric pressure at a particular height, even without use of the device, if you know the pressure at sea level.It needs only some math skills.Take here this formula: P = P0 * e ^ (- Mgh / RT) .In this formula: P - the desired pressure at a height h;
P0 - is the pressure at sea level in Pascal;
M - is the molar mass of air, equal to 0.029 kg / mol;
g - Earth's gravitational acceleration, roughly equal to 9.81 m / s²;
R - is the universal gas constant, taken as 8.31 J / mol K;
T - temperature in Kelvin (for the transfer of ° C To use the formula in
T = t + 273, where t - the temperature ° C);
h - height above sea level, where we find the pressure is measured in meters.