BarometerA barometer is an instrument used to measure atmospheric pressure. It can measure the pressure exerted by the atmosphere using water, air or mercury. Short-term weather changes can be expected from the change in atmospheric pressure. Say no to plagiarism. Get a tailor-made essay on "Why Violent Video Games Shouldn't Be Banned"? Get Original Essay A barometer is an instrument for measuring the pressure of, due to the weight of the column of air above it. Since the Earth's atmosphere thins with increasing height, it follows that as we rise from sea level and from low parts of the Earth's surface, the weight of the air will decrease. That is, the pressure will decrease. Types: water barometers. This concept of "decreasing atmospheric pressure predicts stormy weather" is the basis for a primitive weather forecasting device called weather glass or soft glass. consists of a glass container with a sealed body, half field with water, a narrow spout connects to the body below the water level and rises above the water level, where it is open to the atmosphere. when the air pressure is lower than when the body was sealed, the water level in the spout will rise above the water level in the body, when the air pressure is higher than that of the When the body has been sealed, the water level in the spout will increase the temperature of the water level in the spout. A variant of this type of barometer can be easily constructed. Mercury Barometers A mercury barometer has a glass tube at least 84 cm high, closed at one end, with an open reservoir filled with mercury at the base. The weight of the mercury creates a vacuum at the top of the tube. The mercury in the tube adjusts until the weight of the mercury column balances the atmospheric force exerted on the tank. The high atmospheric pressure exerts a greater force on the tank, pushing the mercury further up the column. The low pressure allows the mercury to drop to a lower level in the column decreasing the force exerted on the reservoir. Since a higher temperature on the instrument will reduce the density of the mercury, the scale for reading the height of the mercury is adjusted to compensate for this effect. One atmosphere's pressure is equivalent to about 29.9 inches, or 760 mm, of mercury. Some barometers provide atmospheric pressure in millibars (one millibar=100 pascals, or one hundred pascals) to convert a reading in inches of mercury to millibars, divide the pressure in inches of mercury by 0.0295. Aneroid Barometer An aneroid barometer uses a small flexible metal box called an aneroid cell. This aneroid capsule (cell) is made up of beryllium and copper alloys. The box is hermetically sealed after it is removed for a period of the year, so that small changes in outside air pressure cause the cell to spend or contract. This expansion and contraction operates mechanical levers and other devices displayed on the front of the anriod barometer. Many models include a manually set needle that is used to mark the correct measurement so you can see a change. Standard Atmospheric Pressure The standard atomsphere (symbol;atm) is a unit of pressure equal to 101325 Pa or 1013.25 millibars or hectopascals. Equivalent to 760 mmHg (torr), 29.92 inHg 14.696 psi. The density of mercury will change with temperature, so you need to adjust the reading based on the temperature of the instrument. For this purpose, a mercury thermometer is usually mounted on the instrument. Since the air pressure will be established at an altitude above sea level (e.g.