Rotameters (Variable Area Flow Meters)

Rotameters for Every Application

Variable area (VA) flow meters, or rotameters, are some of the oldest devices used for flow measurement, known for their flexibility across various applications and high reliability.

Yokogawa VA flow meters offer simple installation and trouble-free operation while delivering highly accurate flow measurements in low flow, high pressure, and other applications. Yokogawa’s rotameter series features various materials and designs including glass, plastic, and metal metering tubes as well as additional features suited for a range of mediums and applications.

Select the ideal rotameter for your process needs.

How Variable Area Flow Meters Work

VA flow meters consist of a cone, float, scale, and process connection. Operating under the variable area flow principle, rotameters use a simple design in which a float rises inside a conically shaped glass tube as the flow increases and its position on the scale gives the flow rate.

  • RAGN

    The RAGN Rotameter is designed for continuous flow measurement of liquids and gases. The borosilicate glass metering tube has a brightly colored easy-to-read scale. In-line 316 stainless steel fittings are standard.

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  • RAMC

    • RAMC Variable Area Flow Meter
    • Variable area principle
    • Robust design
    • Reliable measurement
    • Gas, liquid, steam applications
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  • RAKD

    The RAKD Rotameter is used for measurement of liquids and gases and is highly accurate, particularly for low flows and high pressure applications.

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  • RAGL

    The RAGL rotameters are specifically designed for the measurement of low flows of liquid and gases. Their main application field is in purging, analyzer and gas sampling systems, laboratories and machinery equipment.

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  • RAGK Short Rotameter

    Thie Short Rotameter RAGK is designed for measurement of liquids and gases. The conical glass metering tube has a free rotating float. Measureable Flow Rate: Water = 0.002 l/h to 600 l/h; Air = 0.2 l/h to 6300 l/h

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The measurement technique is dependent on the density, viscosity and temperature of the medium. Exact results can be expected only if the characteristics of the medium remain constant. In the case of metal rotameters such as the RAMC, the special shape of the float results in less dependence on viscosity at lower viscosities.

Download our user-friendly Rotameter Sizing Program to build the correct rotameter for your application.

In the 1990s, Yokogawa strengthened its focus on flow meters through cooperation with and the eventual acquisition of the German flow meter manufacturer ROTA. As a result, Yokogawa gained access to 100 years of flow meter expertise and completed its flow meter portfolio by adding the Rotameter (variable area) and Rotamass (Coriolis) product lines.


rotameter history



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Our experts review the theory behind flow measurement technologies. Discuss common flow application challenges and evaluate the different technologies when selecting a flow meter. They also give examples of best installation practices for successful measurements.

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