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Rotameter- Working Principle, Uses, Pros, Cons, and Handling


A rotameter variety known as a rotameter is also referred to as a variable area flowmeter. In commercial settings, it is used to gauge the velocity of air and liquids (such as water, oil, and others). In addition, it is utilised in medical devices like anaesthesia machines, oxygen tanks, and concentrators. The height and shape of these machines can vary between models, even for the same flow rate. The rotameter’s operating system will be discussed in this section.

In addition, we will discuss the rotameter’s pros, cons, and handling process of the rotameter.


Rotameter Working Principle

An outer vertically tapered glass tube with a wide top and a narrow base makes up a rotameter. It is referred to as a varying area flowmeter because the cross-sectional area of the tube varies. The tube has a measuring float inside. The glass tube has measurements embedded inside of it.


The float rests at the bottom of the tube when there is no fluid movement through the rotameter. The fluid forces the float upward as it enters the tube through the base. The pressure that the fluid applies to the float directly relates to the distance that the float travels from the foundation.


Advantages of Rotameter

A variety of benefits may be associated with the varying area flowmeter. The following list of rotameter’s benefits is provided.


  • It is inexpensive and widely accessible in the market.
  • It offers a linear measurement gauge. As a result,getting a reading is made easier.
  • Rotameter can detect fluids moving at velocities between 1 LPM and 10 LPM. In other words, it is appropriate for measuring fluids moving at low to middle speeds.
  • The rotameter can detect even corrosive fluids. This is due to the metal and glass cover being extremely resistant to different types of chemicals.
  • It offers greater sharpness and accuracy.


Disadvantages of Rotameter

  • The rotameter has some limitations despite being helpful in a variety of situations. Therefore, a few of the drawbacks are listed below.
  • Due to fluid pressure, the outer glass layer is readily breakable. Additionally, while the machine is being transported or maintained, the glass covering may crack.
  • Rotameter ought to be maintained erect. It will result in measurement errors if you angle it.
  • The fluid you’re going to use to gauge velocity needs to be transparent. You won’t be able to see the metering float correctly if you don’t. You won’t be able to take the measurement in that situation.
  • It is not appropriate for fluids moving at a fast speed.
  • There may be a case of parallax error if you do not place your eyes at the same level as the metering float.


Handling process

When using the rotameter, you must be mindful of the following.


  • The rotameter is made of a glass tube, so if you don’t handle it carefully, it could shatter.
  • The flowmeter should not be adjusted to “0” while it is in use. The pressurised air movement will be impeded by this. As a result, it may harm the rotameter permanently. A minimum flow rate of 0.5 gallons per minute is required.
  • While getting the reading, parallax errors must be avoided.
  • The glass’s exterior can be cleaned with an alcohol brush.
  • At the bottom of the flowmeter, the float can occasionally become trapped. The airflow will be obstructed by this. As a result, you won’t get any results from it. In this situation, flip the flowmeter over and attempt to shift the float away from the base. Try using a gust of wind to clear the obstruction if you are unable to invert the flowmeter.
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