Difference Between Manometer and Barometer : Details Discussion

Among these two devices, you can find one of them in many houses, especially in coastal areas with unstable weather. That’s the barometer.

No, you don’t need to be a storm chaser to have a barometer installed in your house. But the other one, manometer? That isn’t as common. It has to do with practical reasons.Difference between Barometer and Manometer

Although they measure pressure, they aren’t quite the same, are they? Even the working principle is the same. So, what exactly is the difference between barometer and manometer?

Well, if you don’t know much about these two devices and how they differ from one another, I think I might be of help.

I’ll be going through each different point about these two devices. So, let’s not waste any more of your time.

First, we’ll go over the details of each of the devices. It’ll help to grasp the core difference between the two. If you don’t want to read the details and want the summary, you can scroll down to our brief comparison section.

Those of you who are nerds, stick with me.

What Is a Manometer?

What Is a Manometer?

A manometer is a device to measure pressure. Its range covers both gaseous and liquid matter, i.e., it measures both gas and liquid. People use it most of the time to measure liquid and gas pressure, but it has more uses, especially in industrial applications.

Working Principle

The working principle of a manometer is simple. It uses a liquid to measure the external force or pressure. This is how it works:

Suppose you have a U-shape tube and put any liquid in the tube. If the liquid reaches the same height in both tubes, then we can say that the pressure exacting on both the tubes is the same, i.e., it's the atmospheric pressure acting on both ends.

We can expand this working principle to measure the pressure of many things!

Measuring Atmospheric Pressure with Manometer

Using manometers to measure atmospheric pressure is possibly an understatement to the potential of this device, but you could if you wanted to.

A closed-tube manometer is a manometer with one of its tubes shut off using glass or a cork. This closed-tube manometer's open-end receives the air pressure, and we examine how much higher it pushes the liquid in the other column.

The difference between the previous and current heights is your atmospheric pressure.

Measuring the Pressure of Another Liquid with Manometer

Things are a bit complex when you want to measure the pressure exerted by a liquid.

You've got your thin U-shaped tube filled with either water or mercury. One end is open as always, but the other end, in this case, isn't closed; rather, it has a funnel with a rubber mask covering the entry.

When you insert the funnel into a liquid, the liquid exerts its pressure onto the rubber mask, which is then transferred to the U-shaped tube. You'll notice that the liquid on the other side has risen. The height difference is the liquid's pressure.

Measuring the Pressure of a Gas with Manometer

Manometers for measuring gaseous pressure are built differently. You still have the same U-shaped tube with liquid, but one end of it has a container that will be filled with a gas of your choice.

The liquid will be at different heights in two tubes. Say, it's A in one tube and B in another. The difference between these two points, i.e. (A-B), is your gas' pressure.

Measuring Positive and Negative Pressure

You can find out whether or not your chosen medium is experiencing negative pressure. It's simple. The liquid's height will change after you connect the manometer to a container filled with liquid or gas. If the height decreases, that means there's negative pressure in the system.

But if the height increases, you have a system experiencing positive pressure.

Where Are Manometers Used?

Manometers are mostly used in industrial applications and many laboratories throughout the world.

For example, U-tube manometers are used in ventilation systems to control airflow. You could use a closed-tube manometer to measure the atmospheric pressure instead of a barometer.

Fluid Used in Manometers

The fluid used in manometers has to be nonvolatile. Furthermore, the liquid can't change its state due to slight temperature differences. And that's why mercury is selected for industrial use. But for experimental setups, you can use water for convenience.

What Is a Barometer?

What Is a Barometer?

A barometer device is used to measure the atmospheric pressure around us. You can see it commonly used to understand the change in weather in a region. It's one of the simpler measuring devices in the chemistry world, but that is what also makes it perfect for everyday use.

How Does it Work?

The barometer is a much simpler tool to measure atmospheric pressure. You only need a flat container and a tube. Both the container and the tube will be filled with the same liquid. The most commonly used liquid is mercury since it retains its liquid nature in most normal temperature conditions.

Once you've filled them, we'll turn the tube upside down and merge its opening with the liquid in the container. This way, the liquid will be connected. Now, we'll measure the height of the liquid in the tube.

This height is the atmospheric pressure of the atmosphere you're experimenting with.

What Do You Measure with a Barometer?

You can measure only the atmospheric pressure with a barometer, unlike you could with a manometer. The working principle of the barometer doesn't allow us to put any liquid in the system to measure its pressure.

Use Cases

Barometers are mainly used to check the weather patterns. Since they're quite accurate at reading the atmospheric pressure change, you can use them to predict the weather behavior.

If you combine the wind observations with your barometric/atmospheric pressure, you can predict whether or not you'll be facing a storm in your locality.

This device is also used to measure an aircraft's speed. It does it by measuring the pressure created by the air when the aircraft cruises through the sky.

Measuring Negative and Positive Pressure

A simple barometer can only measure the positive pressure of the atmosphere. But it can detect whether or not the surrounding is experiencing negative pressure.

If there's no rise in the mercury level, it means the room is experiencing negative pressure. But you can't get a negative reading.

Barometer vs Manometer : What's the Actual Difference?

Now that we've seen what the two devices do and how they work, I think it's a perfect time to point out the actual differences between them.

Design and Construction

They are similar when it comes to how they work with a liquid and the height difference. But there is a fundamental difference between their design and construction.

Manometer's basic design constitutes of a U-shaped tube half-filled with a liquid. On the other hand, a barometer is made with a container and a normal thin tube filled with liquid.

Measuring Capability

They are in two different worlds when it comes to the range of things they can measure. Yes, they both measure air or atmospheric pressure.

But, the manometer's ability to measure liquid gives it a lot of options. One example would be the multi-fluid manometer. That's a complex manometer which is a topic for another time.

Measurement Reading

One other case where they differ is the ability to give a negative reading. Manometer's design allows it to measure the negative pressure in your system. But a barometer can only give you an indication of zero pressure situations.

Situations Where They Are Used

Manometers got a wide range of applications, from industrial machines to measuring optimum conditions of a laboratory.

But barometer is mostly used to forecast weather patterns. On its own barometer can predict immediate weather behavior. But if you keep a history of atmospheric pressure change, it can tell you what will happen in a few days.

And combined with other weather data such as wind speed, you can forecast future rainfall and storms.

Types

Both of these measuring devices can come in different shapes and sizes. But manometer, not surprisingly, has a bit more range.

A barometer is mainly of two types:

  • Mercury barometer

Mercury barometer

It's the basic type of barometer using a container and a tube. And the liquid used in it is mercury, hence its name.

  • Aneroid barometer

Aneroid barometer

An aneroid barometer does not use liquid to measure atmospheric pressure. It's a bit more complex. This device was invented in 1844 and used a small but flexible metal box named an aneroid capsule or cell. The material of this box is an alloy made out of beryllium and copper.

There is another type called a digital barometer, but that's mostly an electronic version of the two above.

But manometers have many types. Among them are:

  • U-tube manometer
  • Enlarged Leg manometer
  • Well Type manometer
  • Inclined Tube manometer

There's another method of division among manometers. That's the open-ended manometer and close-ended manometer.

Here's a brief comparison table between barometer and manometer. I hope this will be helpful.

Characteristics

Availability

Design

Manometer: U-tube


Barometer: Container and a straight tube

Measuring Liquid or Gas Pressure

Manometer: Yes

Barometer: No

Use Cases

Manometer: Industrial applications and labs

Barometer: For weather forecast

Negative Pressure Reading

Manometer: Yes, it gives negative pressure readings

Barometer: No, it can only detect zero atmospheric pressure

Types

Manometer: 4 types

Barometer: 2 types

Manometer and Barometer: Are They Interchangeable?

Since they are similar in some ways but different in others, their interchangeability is very limited. Manometers can do many things that a simple barometer just can't achieve.

But since a closed-end or sealed tube manometer is practically a barometer, you can theoretically and technically use it to take atmospheric pressure readings. But that'll prove to be tough since there are no ready-made manometers like there are barometers for weather forecasting.

The other cases, such as measuring the pressure of a liquid or a gaseous matter, are not possible with a barometer. Hence, their interchangeability is limited to the common characteristics.

Final Words

Despite the similarity in their working principle and pressure measurement, they are entirely two different devices. In most cases, you can't even use one in place of the other. As you can see from the information above, the difference between barometer and manometer is in more than one aspect.

Which one is for you? Only you can decide that. This is not a case of one being better than the other.

If you need to keep a check on the weather changes around you, the barometer is your thing. But if you're someone who works in a lab or in a factory that deals with gases and liquids, you'll be using manometers a lot.

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