What is a Barometer?


A barometer is a scientific instrument used to measure atmospheric pressure. It is an essential tool in meteorology and is used to forecast weather patterns. The word “barometer” comes from the Greek words “baros” meaning weight and “metron” meaning measure. The device was invented in the 17th century by Italian physicist Evangelista Torricelli.

How does a Barometer Work?

A barometer works on the principle that atmospheric pressure changes with altitude. It consists of a long glass tube filled with mercury, which is then inverted into a dish of mercury. The mercury in the tube drops until it reaches a point where the weight of the mercury column is balanced by the atmospheric pressure pushing down on the dish. The height of the mercury column in the tube indicates the atmospheric pressure.

Types of Barometers

There are several types of barometers, each with its own advantages and applications:

  • Mercury Barometer: This is the traditional type of barometer that uses mercury as the measuring fluid. It provides accurate readings but has become less common due to the toxicity of mercury.
  • Aneroid Barometer: An aneroid barometer uses a small, flexible metal box called an aneroid cell that expands or contracts with changes in atmospheric pressure. This movement is then converted into a pressure reading on a dial.
  • Electronic Barometer: Electronic barometers use sensors to measure atmospheric pressure and display the readings digitally. They are more portable and easier to read than traditional barometers.
  • Weather Barometer: Weather barometers are designed specifically for weather forecasting. They often include additional features such as temperature, humidity, and wind speed measurements.

Applications of Barometers

Barometers have various applications in different fields:

  • Meteorology: Barometers are essential tools for meteorologists to measure and monitor changes in atmospheric pressure, which aids in weather forecasting.
  • Aviation: Barometers are used in aircraft to measure altitude and to calibrate altimeters, which provide crucial information for pilots.
  • Research: Barometers are used in scientific research to study atmospheric pressure changes and their impact on the environment.
  • Healthcare: Barometers are sometimes used in medical settings to measure atmospheric pressure changes that can affect patients with certain health conditions.
  • Outdoor Activities: Barometers are popular among outdoor enthusiasts, such as hikers and climbers, as they can help predict changes in weather conditions.
How to Read a Barometer

Reading a barometer requires understanding the scale and markings on the device. Traditional barometers have a scale that measures atmospheric pressure in inches of mercury (inHg) or millimeters of mercury (mmHg). The scale is marked with numbers representing the pressure readings.

When reading a barometer, the mercury level is observed and compared to the scale. The height of the mercury column indicates the atmospheric pressure, with higher columns corresponding to higher pressure. The readings are typically recorded in inches or millimeters of mercury.

Frequently Asked Questions (FAQs)

Q1: Can I use a barometer to predict the weather?

A1: Yes, barometers are commonly used to predict weather changes. A rapid decrease in atmospheric pressure often indicates an approaching storm, while a steady rise in pressure suggests stable weather conditions.

Q2: Is a digital barometer as accurate as a mercury barometer?

A2: Yes, electronic barometers are generally as accurate as traditional mercury barometers. However, it is important to ensure that the digital barometer is calibrated correctly for accurate readings.

Q3: Can a barometer be used to measure altitude?

A3: A barometer can indirectly measure altitude by detecting changes in atmospheric pressure with elevation. However, for precise altitude measurements, specialized instruments like altimeters are more suitable.

Q4: How often should I calibrate my barometer?

A4: It is recommended to calibrate your barometer annually or whenever you suspect it is providing inaccurate readings. Calibration can be done using known pressure references.

Q5: Are there any safety precautions when using a mercury barometer?

A5: Yes, mercury is toxic and should be handled with care. It is advisable to use alternative barometer types, such as aneroid or electronic barometers, to avoid the potential risks associated with mercury exposure.

Q6: Can a barometer be affected by altitude changes?

A6: Yes, barometers are affected by changes in altitude. As you ascend to higher altitudes, the atmospheric pressure decreases, resulting in lower readings on the barometer. Similarly, descending to lower altitudes will result in higher readings.


Barometers are invaluable instruments for measuring atmospheric pressure and predicting weather patterns. They have diverse applications in meteorology, aviation, research, healthcare, and outdoor activities. Understanding how to read a barometer and interpret its readings can provide valuable insights into the current and future weather conditions. While traditional mercury barometers are less common due to their toxicity, modern electronic barometers offer portability and ease of use without compromising accuracy.

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