June 20, 2024

How Does a Rotameter Work and it’s Features

Do you want to know about rotameters and how they work? When measuring liquid flow, a rotameter is an ideal measuring device. Read along to understand more about rotameters.

The fluid flow measurement industry has numerous kinds of water flow instruments used to measure different types of fluids, gases, and steam in different applications. Among them is a rotameter flow measurement device that is commonly used to measure the flow rate of fluids. In this post, we are discussing how a rotameter works when measuring flow rate in liquids. Read on for better insights.

What is a Rotameter?

The name rotameter came from how this measuring device works when measuring flow rate. It has rotating vanes that rotate at different speeds depending on the speed of water passing through it. It is often used to measure liquid flow rate. A rotameter is made up of two main components: a metal float and a tapered or conical glass tube. Depending on the flow rate of the fluid that is passing through the tube, the float will either rise or drop. The tapered tube’s diameter narrows down at the bottom. When there is zero flow rate, the metal float will remain at the bottom. When water or any other fluid flows through the tube, the float will start rising up. Once the weight of the float is balanced by the fluid’s up-thrust, it will stop rising. The position of the float will indicate the flow rate.

The pressure drop in the tube will increase once the flow rate increases. Flow rate readings will indicate the pressure drop is sufficient enough to make the float rise. The working principle of a rotameter is the force exerted by the up-thrust motion of the measured fluid against the force of gravity. A rotameter, which is also called a variable area flow meter, measures water through constriction areas. For a rotameter to give an accurate flow reading, the liquid density to move the float.

How Rotameters are Made

The tapered tube of arotameternarrows down towards the bottom. By varying the cross-sectional area of the tube, it gives a constant pressure drop across the float. There are several materials that can be used to make the conical tube include glass, plastic, or stainless steel. Different materials are used depending on the type of application. If the application is used to process gas or liquid, then the best material to create the tube is glass. Metal gives usually used fur opaque liquids.

Several kinds of materials can be used to create floats of different densities. These types of materials include plastic, aluminum, or glass. The material that is often used to make floats in rotameters is stainless steel. In different applications, the proportion and that and the shape of the float will vary.

How Rotameter Calibration is Done

The first thing that you must do when you want to calibrate a rotameter is to fill the storage tank with fluid. Next, open the bypass valve. Since the rotameter valve was initially closed, you can now open the valve and allow the fluid to flow through the rotameter. As water continues to fill up the rotameter, use a stopwatch to indicate where the float stops. Using the same process, keep on increasing the flow rate and mark the float’s position in each test.

Rotameter Types

  • Glass Tube Rotameter

Since this type of variable area flow meter is made up of transparent glass, you will be able to see the float. It has high repeatability, and it is very easy to use when you measure flow rate. There is a scale on the tube’s surface for indicating flow rate readings.

  • Metal Tube Rotameter

It is usually called an armored flow meter and is used in applications that won’t work well with glass material. This is due to very high temperatures and pressure that may break the glass. With the help of a magnet that is inserted inside the float, the pointer can indicate the position of the float. There is no need for external power while using the metal-type rotameter.

  • Plastic Tube Rotameter

This is the cheapest kind of rotameter and is used in various types of fluid measurements. Many industrial applications use these types of flow meters.

  • Purgemeters

When you want to use these types of variable area flow meters, then it has to be with a smaller application. The reason being that they are used to measure low flow rates of gases and liquids. Even in low flow rates, this rotameter is capable of giving accurate readings.


That is all we had for today about rotameters. We hope that you are now well informed of what a rotameter is and how it works. All that is left now is getting your rotameter. You can ask the manufacturer for assistance when choosing the right flow meter.

Naman Modi

Naman Modi is a Professional Blogger, SEO Expert & Guest blogger at NamanModi.com, He is an Award Winning Freelancer & Web Entrepreneur helping new entrepreneur’s launches their first successful online business.

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