Inst ToolsInst ToolsInst Tools
  • Courses
  • Automation
    • PLC
    • Control System
    • Safety System
    • Communication
    • Fire & Gas System
  • Instrumentation
    • Design
    • Pressure
    • Temperature
    • Flow
    • Level
    • Vibration
    • Analyzer
    • Control Valve
    • Switch
    • Calibration
    • Erection & Commissioning
  • Interview
    • Instrumentation
    • Electrical
    • Electronics
    • Practical
  • Q&A
    • Instrumentation
    • Control System
    • Electrical
    • Electronics
    • Analog Electronics
    • Digital Electronics
    • Power Electronics
    • Microprocessor
  • Request
Search
  • Books
  • Software
  • Projects
  • Process
  • Tools
  • Basics
  • Formula
  • Power Plant
  • Root Cause Analysis
  • Electrical Basics
  • Animation
  • Standards
  • 4-20 mA Course
  • Siemens PLC Course
Reading: Types of Variable Area Flow Meters
Share
Notification Show More
Font ResizerAa
Inst ToolsInst Tools
Font ResizerAa
  • Courses
  • Design
  • PLC
  • Interview
  • Control System
Search
  • Courses
  • Automation
    • PLC
    • Control System
    • Safety System
    • Communication
    • Fire & Gas System
  • Instrumentation
    • Design
    • Pressure
    • Temperature
    • Flow
    • Level
    • Vibration
    • Analyzer
    • Control Valve
    • Switch
    • Calibration
    • Erection & Commissioning
  • Interview
    • Instrumentation
    • Electrical
    • Electronics
    • Practical
  • Q&A
    • Instrumentation
    • Control System
    • Electrical
    • Electronics
    • Analog Electronics
    • Digital Electronics
    • Power Electronics
    • Microprocessor
  • Request
Follow US
All rights reserved. Reproduction in whole or in part without written permission is prohibited.
Inst Tools > Blog > Flow Measurement > Types of Variable Area Flow Meters

Types of Variable Area Flow Meters

There are two Types of Variable Area Flow Meters. Classification of Area flow meters are Rotameter and Piston type flow meter.

Last updated: November 2, 2023 10:09 am
Editorial Staff
Flow Measurement
No Comments
Share
5 Min Read
SHARE

In this type of orifice meter, there is a fixed aperture, and flow is indicated by a drop in differential pressure. In the area meter, there is a variable orifice and the pressure drop is relatively constant.

Contents
Types of Variable Area Flow MetersRotametersPiston Type MeterPerformance CharacteristicsLinearityDifferentialAccuracyCapacityMinimum Piping RequirementCorrosive or Difficult-to-handle liquidPressure Drop

Thus, in the area meter, flow is indicated as a function of the area of the annular opening through which the fluid must pass. This area is generally readout as the position of a float or obstruction in the orifice.

The effective annular area in the area meter is nearly proportional to the height of the float, plummet, or piston, in the body, and the relationship between the height of the float and flow rate is approximately linear one with linear flow curves as well as scale graduations.

Types of Variable Area Flow Meters

Area meters are of two general types :

  1. Rotameters and
  2. Piston type meter.

Rotameters

In rotameter, a weighted float or plummet contained in an upright tapered tube, is lifted to the position of equilibrium between the downward force of the plummet and the upward force of the fluid in addition to the buoyancy effect of the fluid flowing past the float through the annular orifice.

The flow rate can be read by observing the position of the float.

Piston Type Meter

In this meter, a piston is accurately fitted inside a sleeve and is lifted by fluid pressure until sufficient post area in the sleeve is uncovered to permit the passage of the flow. The flow is indicated by the position of the piston.

Fig. shows the types of Variable area flow meters (a) Rotameter and (b) Piston Type meter.

Piston Type Flow Meter Principle

Performance Characteristics

The performance characteristics are discussed with reference to the below factors.

  • Linearity
  • Differential
  • Accuracy
  • Capacity
  • Minimum Piping Requirement
  • Corrosive or Difficult-to-handle liquid
  • Pressure Drop,

Linearity

The flow rate (volume) through a variable area meter is essentially proportional to the area and, as a result, most of these meters have essentially equal-scale increments.

A typical indicating rotameters scale is non-linear by about 5%.

Differential

An important characteristic of the variable area meter is that the pressure loss across the float is constant.

The overall differential across the meter will increase at higher flow rates because of friction losses through the fittings.

Accuracy

The most common accuracy is ±2% of full-scale reading. This increases considerably with individual calibration and scale length. Repeatability is excellent.

Capacity

Variable area flow meters are the most commonly used means for measuring low-flow rates.

Full-scale capacities range from 0.5 cm3/min of water and 30 std cm3/min of air in the smallest units to over 1200 liters/min of water and 1700 m3/h of air in 8 cm height meters.

Minimum Piping Requirement

An area meter usually can be installed without regard to the fittings or lengths of straight pipe proceedings or following the meter.

Corrosive or Difficult-to-handle liquid

These can often be handled successfully in an area meter. They include such materials as oil, tar, refrigerants, sulphuric acid, black liquor, beverages, aqua regia, and molten sulphur.

In general, if the nature of the fluid does not permit the use of a conventional differential pressure type meter because the fluid is dirty, viscous, or corrosive, certain area meters have an advantage over other types of meters.

Pressure Drop

By placing very light floats in oversized meters, flow rates can be handled with a combination of very low-pressure loss (often 2.5 cm of water column or less) and a 10:1 flow range.

If you liked this article, then please subscribe to our YouTube Channel for Instrumentation, Electrical, PLC, and SCADA video tutorials.

You can also follow us on Facebook and Twitter to receive daily updates.

Read Next:

  • Transit Time Flow Meter
  • Vortex Flow meter Animation
  • Ultrasonic Flow Meters
  • Venturi and Orifice flow meter
  • Calibrate Flow meters
Don't Miss Our Updates
Be the first to get exclusive content straight to your email.
We promise not to spam you. You can unsubscribe at any time.
Invalid email address
You've successfully subscribed !

Continue Reading

Volumetric Flow Calculations
Interferometer Principle
Annubar Flow Meter – Principle, Advantages, Disadvantages
Oval Gear Meter – Principle, Advantages, Limitations, Applications
What is Gas Meter and Regulating Station?
Why Turndown Ratio is important when Selecting a Flow Meter?
Share This Article
Facebook Whatsapp Whatsapp LinkedIn Copy Link
Share
Leave a Comment

Leave a Reply Cancel reply

Your email address will not be published. Required fields are marked *

Stay Connected

128.3kFollowersLike
69.1kFollowersFollow
210kSubscribersSubscribe
38kFollowersFollow

Categories

Explore More

Orifice Plate Turndown ratio
What is Differential Pressure Flow Meter?
What are Multiphase Flow Meters? – Working Principle, Advantages
Nutating Disc Flow Meters Working Principle
DP Flow Transmitter Re-Ranging Calculation
What is Water Cut Meter?
Spring Loaded Variable Area Flow Meter Working Principle
Thermal Dispersion Flow Switch Working Principle

Keep Learning

Turbine Flow Meter Animation

Turbine Flow Meter – Principle, Advantages, Disadvantages

Swirl Flowmeters Principle

Swirl Flow Meters Working Principle

Target Meter Principle

Target Flow Meter – Working Principle, Advantages, Disadvantages

Advantages and Disadvantages of Flow Measurement Techniques

Advantages & Disadvantages of Different Flow Meters

V Cone Flow Meter Working Principle

V Cone Flow Meter – Principle, Advantages, Disadvantages

Difference between Orifice & Restriction Orifice

difference between invasive and non-invasive and intrusive and non-intrusive

Difference between Invasive, Non-invasive, Intrusive & Non-intrusive

Coriolis Mass Flow meter as a Multi Variable Transmitter - 2

Coriolis Flowmeter Advantages and Limitations

Learn More

Electrical Machines Questions and Answers

Reluctance Motor Quiz

PLC Automation Memory

What is NOR Flash Memory in PLC?

Differential Pressure Transmitter Manifold

Field Instrument Calibration Errors

Conductive Level Switch Principle

Conductive Level Switch Principle

Economizer

What is an Economizer? Purpose, Classification, Advantages

Allen Bradley PLC communication is established

Procedure for Connecting Allen Bradley PLC and PC – RS Logix 500

pressure gauge snubber

Pressure Gauge Snubbers

half-wave-rectifier-working-animation

Half Wave Rectifier Principle

Menu

  • About
  • Privacy Policy
  • Copyright

Quick Links

  • Learn PLC
  • Helping Hand
  • Part Time Job

YouTube Subscribe

Follow US
All rights reserved. Reproduction in whole or in part without written permission is prohibited.
Welcome Back!

Sign in to your account

Username or Email Address
Password

Lost your password?