Inst ToolsInst ToolsInst Tools
  • Ask
  • Courses
  • Videos
  • Q & A
    • Interview
      • Instrumentation
      • Electronics
      • Electrical
      • Practical Questions
    • MCQ
      • Instrumentation MCQ
      • Electrical MCQ
      • Electronics MCQ
      • Control Systems MCQ
      • Analog Electronics MCQ
      • Digital Electronics MCQ
      • Power Electronics MCQ
      • Microprocessor MCQ
      • Multiple Choice Questions
  • EE
    • Electronics
      • Electronics Q & A
      • Electronic Basics
      • Electronic Devices & Circuits
      • Electronics Animation
      • Digital Electronics
    • Electrical
      • Electrical Basics
      • Electrical Q & A
      • Power Electronics
      • Electrical Machines
      • Electrical Animation
      • Power Systems
      • Switchgear & Protection
      • Transmission & Distribution
  • Measure
    • Control Valves
    • Calibration
    • Temperature
    • Pressure
    • Flow
    • Level
    • Analyzers
    • Switches
    • Vibration
    • Solenoid Valve
  • Control
    • PLC Tutorials
    • Control Systems
    • Safety Instrumented System (SIS)
    • Communication
    • Fire & Gas System
  • More
    • Design
    • Tools
    • Animation
    • Basics
    • Formulas
    • Standards
    • TextBooks
    • Common
    • Software
    • Excel Tools
    • Erection & Commissioning
    • Process Fundamentals
    • Videos
    • Books
Search
All rights reserved. Reproduction in whole or in part without written permission is prohibited.
Reading: Types of Variable Area Flow Meters
Share
Notification Show More
Font ResizerAa
Inst ToolsInst Tools
Font ResizerAa
  • Courses
  • PLC Tutorials
  • Control Systems
Search
  • Ask
  • Courses
  • Videos
  • Q & A
    • Interview
    • MCQ
  • EE
    • Electronics
    • Electrical
  • Measure
    • Control Valves
    • Calibration
    • Temperature
    • Pressure
    • Flow
    • Level
    • Analyzers
    • Switches
    • Vibration
    • Solenoid Valve
  • Control
    • PLC Tutorials
    • Control Systems
    • Safety Instrumented System (SIS)
    • Communication
    • Fire & Gas System
  • More
    • Design
    • Tools
    • Animation
    • Basics
    • Formulas
    • Standards
    • TextBooks
    • Common
    • Software
    • Excel Tools
    • Erection & Commissioning
    • Process Fundamentals
    • Videos
    • Books
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 !
Square-root characteristics of Differential Pressure Flow Meters
Factors Affecting the Performance of Ultrasonic Flow Meters
How does an Orifice Measures Flow?
Magnetic Flow Meter Corrosion Effects
Interview Questions on Flow Measurement
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
208kSubscribersSubscribe
38kFollowersFollow

Categories

Recent Comments

  • Guifty Shimica on Top Non-PLC Certification Courses for Automation Professionals
  • Guifty Shimica on Top Non-PLC Certification Courses for Automation Professionals
  • MIHARITSOA Aina Sitraka on Top Non-PLC Certification Courses for Automation Professionals
  • Vaishnavi on Free Instrumentation Course for Trainee Engineers

Related Articles

Turbine Meter in Gas Metering System

Read Gas Composition from Gas Metering System using RS485 Protocol

Hot wire Anemometer Principle

Hot Wire Anemometer Principle and Types

Thermal Mass Flowmeter Principle

Thermal Mass Flow Meter – Principle, Advantages, Applications

Venturi Flow Meter

Venturi Flow Meter – Working Principle, Advantages, Animation

Beta ratio ( β )

Important Factors in Flow Measurement

orifice plate vent hole

What is the Purpose of Orifice Plate Drain Hole and Vent Hole?

Flow Standards

Flow Standards

Target Meter Principle

Target Flow Meter – Working Principle, Advantages, Disadvantages

More Articles

What is Process Control ?

What is Process Control?

Dataloggers Objective Questions

Data Loggers Objective Questions

Bias in Proportional Controller

Why Bias used in Proportional Controller ?

Pressure Gauge Accessories

Pressure Gauge Accessories Questions and Answers

Peripheral Inputs and Outputs in Siemens PLC

Peripheral Inputs and Outputs in Siemens PLC

smart-transmitters-advanced-diagnostics

Smart Transmitters Advanced Diagnostics

What is HIPPS System in Oil and Gas

What is HIPPS System in Oil and Gas?

Understanding RS-485 Communication

Understanding RS-485 Communication

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?