What is a rotameter flow meter?

Rotometer, also known as Float Type Flowmeter, is widely used in industry. It can measure the flow of liquid, gas and steam, and it is suitable to measure the flow of small and medium pipe diameters (DN4 ~ 250).

The rotor flowmeter measures the fluid flow according to the throttling principle. But it changes the flow area of ​​the fluid to keep the differential pressure above and below the rotor constant. Therefore, it is also called a variable flow area constant differential pressure flowmeter, also known as a float flowmeter.

What Is Difference Between Rotameter and Flow Meter?

Featured Flow Meters

working principle of rotameter

Rotameter flow meter structure

A Rotameter flow meter is a variable area flow meter. It consists of measuring tube, float, indicator, process connection, and so on.

Rotameter flow meter working principle

When the measured fluid passes through the annulus formed by the cone and floats from the bottom to top.

The differential pressure produced at the upper and lower ends of the float forms the force for the float to rise.

When the rise of the float is greater than the weight of the float immersed in the fluid. The float rises.

The annulus area increases accordingly. The fluid velocity in the annulus drops immediately.

The differential pressure at the upper and lower ends of the float is reduced. The lifting force acting on the float also decreases.

Until the rising force equals the weight of the float immersed in the fluid, the float will stabilize at a certain height.

The height of the float in the tapered tube and the flow rate through it correspond to each other.

Extended reading: Beginner’s Guide: Variable area flow meter

Rotameter Types

Transparent conical tube rotameter The most widely used material for transparent conical tube is glass. When the instrument without guide structure measures gas, the glass tube is easily broken. Transparent engineering plastics such as polystyrene and polycarbonate are also used. , plexiglass, etc., with the advantage of not easily broken.

Compared with the transparent conical tube rotameter, the metal tube conical tube rotameter can be used for higher medium temperature and pressure. And there is no potential danger of the glass tube rotameter cone being broken.

(1) Local indication type rotameter Some transparent tube rotameters are mainly based on local indication, and are equipped with proximity switches to output the upper and lower limit alarm signals of the flow. Some local indicating metal tube rotameters have the same shape as the remote signal output. Only the rotor displacement is transmitted through magnetic coupling. After being processed by a linearization mechanism such as a connecting rod cam, it is indicated on the spot.

(2) Remote signal output type rotameter The conversion part of the remote signal output type instrument converts the rotor displacement into current or air pressure analog signal output. They become electric remote rotameter and gas remote rotameter respectively.
Read More about: Digital Rotameter

Rotameter output signal, such as 4-20mA, pulse signal, etc. Both can connect the Rotameter flow signal to the paperless recorder. Carry out multi-channel flow signal monitoring. The Use Of Recorder For Process Measurement And Control Instrument:

It is divided into three types: liquid, gas and steam.

In fact, the same instrument of most rotameters can be used for liquid or gas, and the structure is universal.

It is just that the industry standard of my country’s rotor flowmeter (such as JB/T6844-93) stipulates that the upper limit of flow Qmax must meet the requirements of (1, 1.6, 2.5, 4 or 6) × 10nL/h (n is a positive or negative integer or zero). When the instrument designed for liquid (represented by water) is used for gas (represented by air), it does not meet the above requirements. Only a float and a conical tube can be designed for gas. It is divided into two series of liquid and gas.

In some manufacturers, the flow ranges of liquid and gas are paralleled in the same instrument. Of course, the flow values ​​cannot be all rounded values. However, there are still differences in the design of liquid and gas. For example, the gas instrument rotor is designed to be lighter and prevent The structure of the damping member for the oscillation and beating of the float varies.

Only specially designed metal tube rotameters can be used to measure steam or additional components can be added to standard instruments. For example, liquid damping parts with heat sinks are added to reduce float jumps. Heat sinks are separated from the connection with the indication conversion part.

Extended reading: Flow totalizer working principle

1) Full flow type
That is, all the fluid to be measured flows through the meter of the rotameter.

2) Shunt type
Compared with the full flow type, only part of the measured fluid flows through the flow detection part such as the rotor. The split-flow type rotameter is composed of a standard orifice plate (or an equal-velocity tube) on the main pipeline and a small-diameter rotameter. It is suitable for large flow with a pipe diameter greater than 50mm and places where local indication is required, and the price is low. The split flow rotor flowmeter is divided into two types: separate type and integrated type.

What Is Difference Between Rotameter and Flow Meter?

Q: What is the difference between an orifice flowmeter and a rotameter that measure the flow of media?

A: Simply put, the rotor flowmeter uses the gravity of the rotor to measure the flow, and the orifice plate uses the pressure difference before and after the fluid to measure the flow.

  1. Different functions

Rotameters measure fluid flow according to the throttling principle. But it changes the flow area of ​​the fluid to keep the differential pressure above and below the rotor constant. Therefore, it is also called a variable flow area constant differential pressure flowmeter, also known as a float flowmeter.

Orifice flowmeter is a high range ratio differential pressure flow device composed of standard orifice plate and multi-parameter differential pressure transmitter (or differential pressure transmitter, temperature transmitter and pressure transmitter). It can measure the flow of gas, steam, liquid and natural gas.

  1. Different functions

Rotameter is a kind of flowmeter commonly used in industry and laboratories. It has the characteristics of simple structure, intuitive, small pressure loss, convenient maintenance and so on. The rotor flowmeter is suitable for measuring small flow through the pipe diameter D<150mm, and it can also measure the flow of corrosive medium.

The throttling device of the orifice flowmeter has a simple structure, is firm, and has stable and reliable performance. It has a long service life and a low price, and is a commonly used flow measuring instrument in the industry. The entire processing process adopts international standards and undergoes strict calibration and testing.

Extended reading: Liquid mass flow controller for process liquid -Sino-Inst

The working principle of the rotameter is to calculate the flow rate of the medium through the annular gap area between the float and the conical pipe. The turbine flowmeter calculates the flow rate of the fluid by proportional to the rotational angular velocity of the turbine and the fluid velocity. They are in There are also big differences in other respects.

Rotameter and turbine flowmeter are modern and new precision industrial measuring instruments. Although they are both used to measure the flow of media, they are different in working principle, manufacturing process, appearance structure, and performance. However, they all have Small size, simple structure, wide measurement range, long service life and other advantages. The only disadvantage of them is that they are only suitable for the measurement of fluid medium flow in small diameter pipes.

Extended reading: Quantitative control with turbine flowmeter

The difference between mass flowmeter and rotameter:

  1. In terms of accuracy, the mass flowmeter can be controlled to 0.1ml/min,
  2. The mass flow meter controls the pressure, and different pressure-resistant mass flow meters are selected according to different pressures.
  3. Generally, the pressure resistance of the rotor flowmeter should be less than 10atm, while the mass flowmeter can reach 10MPa, and most of them are resistant to 10MPa.

The difference between a mass flowmeter and a rotameter is obvious. The mass flowmeter has high accuracy and may have a large pressure loss. Therefore, as long as the furnace ventilation is controlled, the rotameter is sufficient.

More about: Volumetric Flow Rate To Mass Flow Rate


Yes, Rotameter is a commonly used flowmeter. It is suitable for liquid and gas volumetric flow measurement and control.

In a vertical conical tube that expands from bottom to top, the gravity of the circular cross-section float is supported by hydrodynamic forces. The float can rise and fall freely within the conical tube. It moves up and down under the action of flow rate and buoyancy. After balancing with the weight of the float, it is transmitted to the dial to indicate the flow through magnetic coupling.

Generally divided into glass and metal rotameters. Metal rotameters are the most commonly used in the industry. Glass materials are usually used for corrosive media with small diameters. Due to the fragility of glass materials, rotameters made of precious metals such as titanium are also used for key control points. .

No. Rotameters are not mass flowmeters.

Mass flowmeter and rotor flowmeter are both types of flowmeters. Mass flowmeter generally refers to a flowmeter that can directly measure mass flow readings.

The rotameter uses a float in a vertical conical tube to rise and fall with the flow change. A volumetric flow meter that changes the area of the circulation annulus formed between them to measure.

These two flowmeters are completely different, and users should not confuse them when using them.

Rotameters are devices that can measure the flow of liquids and gases.

Typically, a rotameter is a tube made of plastic, glass or metal combined with a float. It responds linearly to the fluid flow in this tube.

Read more: Metal Tube Flow Meter Applications

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Sino-Inst offers over 30 Rotameter flow meter products. About 50% of these are for liquids. 40% are for gas. At best price.

You can refer to the product price of the following Rotameter flow meter price:

Metal rotor flowmeter
Pipe size 1 inch
FOB Price: USD 381.50/pc~USD699.00/pc;

A wide variety of Rotameter flow meter options are available to you, such as free samples, paid samples.

Sino-Inst is a globally recognized supplier and manufacturer of Rotameter flow meters, located in China.

The top supplying country is China (Mainland), which supply 100% of the Rotameter flow meter respectively.

Sino-Inst sells through a mature distribution network that reaches all 50 states and 30 countries worldwide. Rotameter flow meter products are most popular in Domestic Market, Southeast Asia, and Mid East.

You can ensure product safety by selecting from certified suppliers, with ISO9001, ISO14001 certification.

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