Flow Measurement methods | Flow measuring instruments, devices
This page describes flow measurement basics including methods,instruments and devices. It covers flow measurement methods, flow measuring instruments or flow measuring devices.
Introduction:
The flow of material in a process can be measured by variety of methods which depends on its condition and material, the type of flow,
volume, range and rangeability, pressure, temperature, accuracy and control needed.
The characteristics of flow can be determined based on Reynold's number as expressed below.
Flow Measurement Methods
Following are the flow measurement methods commonly used for flow related measurements.
• Variable head flow meters:
These meters use obstruction in the fluid path. This creates differential pressure across it which
is used as measure of fluid flow.
It includes venturimeter, Orifice meter, Flow nozzle, Pitot tube
• Variable area and variable head flow meters: Weirs, Flumes
• Variable area type flowmeters: Rotameter, Turbine flowmeter, Ultrasonic flowmeter,
Laser Doppler Aneamometer (LDA)
Flow Measuring Instruments | Flow Measuring Devices
Following table mentions flow measuring instruments or flow measuring devices with description.
| flow measuring instruments or flow measuring devices | Description |
|---|---|
| Venturimeter | It is used for measurement of discharge through the pipe. It works based on Bernoull's principle. It has higher sensitivity and can be used in any position. It is used for measurement of water, gases, liquids, slurries etc. |
| Orifice meter | It is used for measuement of volumetric flow rate. It also works on Bernoull's principle. Different types of orifice plates are used in these meters for various applications. |
| Flow Nozzle | It is similar to venturimeter but does not have diverging zone. It uses lesser jet contraction unlike Orifice meter. |
| Pitot tube | It works on principle of "Transformation of kinetic energy of liquid into its potential in the form of static head". It consists of two concentric tubes. |
| Weirs | These are devices which are commonly used for flow measurement of open channel or open stream. There are different types of weirs based on their notches viz. rectangular, V-type, trapezoidal etc. They are used in water works, waste & sewage systems. They can measure flow ranging from flow litres/minute to millions of liters/day. |
| Flumes | Its sizes are arranged to form inlet and throat in which throat is thinner in size compare to inlet. This create shape similar to venturi. Hence it is known as venturi-flume. |
| Rotameter | It is constant pressure drop type variable area flowmeter. In this flowmeter, fluid flows from bottom to top part. |
| Electromagnetic flowmeter | It is non-obstruction type flowmeter. It is used to measure flow of slurries and electrically conductive liquid. It consists of non-conducting and non-magnetic pipe which is surrounded by electromagnet. The magnet produces magnetic field. |
| Turbine flowmeter | It is volumetric flowmeter. In this meter, small turbine wheel is placed in the pipe along the path of the fluid flow. |
| Ultrasonic flowmeter | It uses ultrasonic transducer or piezo-electric crystal. It measures average velocity along the path of emitted beam of ultrasonic waves. The crystal is placed in various arrangements in the tube. |
| Laser Doppler Aneamometer (LDA) | It uses laser beam. The beam is focused at a point where velocity of flow is to be measured. |
Links to useful Measurements
Following are the links to other useful measurements available on Test and Measurement World website.
Difference between EVM vs subcarriers and EVM vs symbols
Current measurement vs Voltage measurement
Inductance measurement vs Capacitance measurement
Difference between Power and Energy measurements
EMC measurement vs EMI measurement
Electric and Magnetic Field Measurements
What is difference between or comparison between
Following links mention difference or comparison between various equipments:
comparison between VSG and VSA
DIfference between SNA ans VNA
Oscilloscope Bandwidth versus Rise time
Oscilloscope vs Logic Analyzer
Difference between Oscillscope types
Comparison between spectrum and network analyzer