What Does A Barometer Measure? How & Where Is It Used?

What Does A Barometer Measure?


  1. Introduction
  2. What is a barometer and how does it work?
  3. How to use a barometer?
  4. Applications
  5. Conclusion


Nowadays, to know what weather to expect before leaving your house, you can do a few things: look out of your window, look at the thermometer, check the weather forecast, etc.

However, a reliable way to know if you are going to get soaked in the rain or not is using a barometer.

What is a barometer and how does it work?

A barometer is an instrument that measures atmospheric pressure (also called barometric pressure). In other words, it measures the weight of the atmosphere pressing down towards the earth.

The higher the barometric pressure, the better the weather. In case the pressure is low, the air is rising away from the earth and you should be prepared for a cloudy and/or rainy weather (sometimes, even hurricanes).

There are analog and digital barometers.

Analog devices are further divided into mercury and aneroid barometers.

A mercury barometer is essentially a container with mercury & a tube. When the atmosphere pushes down on the container filled with mercury, it rises up in the tube. When the atmospheric pressure falls, the air becomes lighter and the level falls. 1 atmosphere (1 atm) is equivalent to 29.92 inches (760 mm) of mercury.

Analog devices are further divided into mercury

An aneroid barometer has an airtight metal box inside. When the air pressure rises, the box squashes inward. When the pressure falls, the box flexes outward. There is a spring that is attached to the box. Depending on the movement of the box, it either expands or contracts. As a result, the pointer on the barometer dial is moving.

the pointer on the barometer dial is moving

An aneroid barometer does not contain liquid so in case it falls, no liquid will spill over.

Today, digital barometers are widely used. They are user-friendly and accurate as well.

Let’s consider the working principle of digital barometers with synthetic rubber sensors. As the air pressure changes, a rubber membrane (red at the top of the diagram) flexes in and out. As a result, its electrical resistance changes. A Wheatstone-bridge type of electric circuit connected to the membrane (gray/blue at the bottom of the diagram) measures the resistance. Then, the chip converts it into a pressure measurement that you can see on the display of your barometer.

Barometer sensors

If you are an owner of a digital barometer, taking readings is easy as ABC. There are neither scales nor needles. You don’t need to figure out how to calibrate your device. A digital barometer has special sensors so the altitude is calibrated automatically.

On the display, there will be the pressure readings. There are barometers that also display barometric pressure trends in a bar graph format.

thermo hygrometer display

As a rule, a digital barometer has an advantage of saving readings, with some models, you can also download data to your PC. Read the manufacturer’s instructions before using your barometer.

There are also devices that combine two or more meters in one. For example, there are thermo hygrometers and barometers. Such devices can measure air temperature, pressure, and relative humidity.

How to use a barometer?

How to use an aneroid barometer?

Step 1 - Set your barometer

1. Get a local reading of barometric pressure

barometric pressure

In case you have an aneroid barometer, its calibration to your location is required. You need to find the current barometric pressure specifically for your location. You can find this information on the Internet.

Why setting your barometer to a specific location is important? This way, you will factor in the differences in pressure that are caused by the altitude of your location.

2. Set the indicator hand on the barometer

Set the indicator hand on the barometer

On the back of the barometer, there is an adjusting screw. Get ascrewdriver and turn the adjusting screw so the hand of the barometer is moved to the current pressure of your location. Turn the screwdriver until you reach the reading you need.

3. Hang your barometer on the wall

Hang your barometer on the wall

It is recommended to avoid locations that are exposed to direct sunlight as temperature changes may affect the readings. In addition, a room with a turned on air conditioner is also not the best choice to place your barometer. In this case, the room won’t be affected by changes in air pressure as it is required.

4. Check if your barometer works the right way

Check if your barometer works the right way

Slide the bottom of the barometer sideways to a 45° angle.

The indicator hand of your aneroid barometer should rotate clockwise around the dial. If it does, everything’s OK. Otherwise, a professional should examine your barometer to fix the problem.

Step 2 - Use your barometer

1. Set the manual hand to the current reading

Set the manual hand to the current reading

Make sure that the arrow is directly above the indicator arrow by turning the center knob of your barometer. The set hand will help you understand if the pressure is rising, falling, or steady.

2. Wait for an hour and check your barometer

Wait for an hour and check your barometer

You have to figure out if the pressure is staying the same or changing.

Try tapping a little your barometer. This way, you can check whether your barometer is working or not. Pressure changes stored in the mechanisms of you barometer should be released.

3. Write down the changes in pressure

Write down the changes in pressure

Get a notebook and keep all the readings that you take with the barometer there. You can draw a graph to monitor the changes during the day (if the pressure is staying the same or rising/falling).

Take readings every few hours. Note that the changes will seem insignificant. However, you should pay attention to the direction in which the needle of your barometer is moving. This will help you forecast the weather.

It is recommended to read the barometer every day at the same time.

Step 3 - Predict the weather using your aneroid barometer

Predict the weather using your aneroid barometer

If your barometer shows that the pressure is falling, the weather is going to be rainy and/or stormy. If the air pressure rises, you will see that the weather is improving.

How to read a barometer?

Look at the table below to know how to interpret the barometer readings you have.

Under 29.80 inHg29.80 - 30.20 inHgOver 30.20 inHg
Steady / Rising Pressure Clearer & cooler weather Present conditions Fair weather will continue
Slowly Falling Pressure Rain Almost no change in the weather Fair weather
Quickly Falling Pressure Storm Rain or snow Cloudy & warmer weather


Barometer use

Barometers are used in various applications. For example, they can be purchased for home use, for your recreational boat, you can get a barometer for fishing, etc. Barometers are purchased for professional use. These devices are used by meteorologists, scuba divers, the list goes on. Barometers can come in handy for educational purposes.

Digital barometers are used in weather stations, GPS devices, airplanes, environmental monitoring devices, the list goes on.


We hope that after reading this article, you know what a barometer is and how it works, how to use this device and where the measurements can be applied.

If you are looking for a barometer, make sure you get a reliable one so you can count on the measurements. On Mega Depot, choose from a selection of best-in-class barometers. Get the product that meets your needs.

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