A barometer measures and displays the pressure exerted by the atmosphere. Depending on the altitude and temperature, slight differences in reading will show in the barometer. The baseline for atmospheric pressure is at sea-level.
At a high altitude such as a climber on top of a mountain, the atmospheric pressure is lower. Planes are pressurized when flying at high altitudes to prevent altitude sickness, like those experienced by Mount Everest. Temperature also affects the measurement, and cold air is denser, so it raises atmospheric pressure.
There are several barometer types, mercury, the aneroid barometer, and electronic. The mercury barometer uses the height of a glass tube filled with liquid mercury to measure atmospheric pressure.
Aneroid barometers, on the other hand, uses a dial and a needle to display atmospheric pressure. The needle is connected to a metal diaphragm that expands and contracts as it reacts to the atmospheric pressure.
Technological advances have given rise to the latest Electronic Barometer. This barometer uses an electronic sensor to measure atmospheric pressure changes and displays them on an LCD screen.
When the barometer reading is high, it usually means the air is cool and dry and indicates fair weather. When the barometer suggests a pressure drop, there is a probability of an approaching storm coming. If it’s steady and stock, then the temperature is also stable. The barometer is one of the tools used for weather forecasting.
How to set a barometer
To have an accurate reading and tell if the atmospheric pressure is falling or rising, you need to set or calibrate the barometer properly.
- Find the local reading of atmospheric pressure and make it your baseline data. You will find this data through the local weather forecast on television, radio or online weather sites. Find the nearest location of the reading, using data from places miles away may affect the readings.
- Set the indicator needle in you barometer and locate a small adjustment screw usually situated in the barometer’s back. Turn the screw using a screwdriver to move the hand to the barometric pressure of your current location. Do it slowly and make sure you are looking at the dial. For mercury barometers, you need to convert the readings before adjusting. Digital barometers, on the other hand, can calibrate the altitude automatically.
- Hang the barometer in a convenient location where you can easily see it. It does not matter if you place it indoors or outdoors since the readings will still be the same. But it’s safer inside to protect it from the elements. Don’t put the barometer in direct sunlight and windy locations like a window or doors.
- Make sure you check the barometer occasionally to make sure they are working correctly. Once in a while, compare your barometer’s reading with local readings. You can check if they are working by slowly sliding the bottom sideways into a 45-degree angle. In a mercury barometer, the mercury will rise on top of the tube. If it’s an aneroid barometer, the indicator needle will rotate clockwise direction around the dial. If the barometers do not pass this test, you need to go to the service center for a check-up and possible repair.