A flow meter is a device that measures the volume or mass of gases and liquids, with various types including velocity, open channel, differential pressure, positive displacement, and mass flow meters. Key considerations for selecting a flow meter include understanding the requirements, evaluating installation, and not just opting for the least expensive option, as this can lead to higher future costs. Flow meters consist of three main parts: the primary device, transducer, and transmitter, which work together to provide accurate flow measurements.

1. WORKING OF A FLOW METER

2. Introduction
 A device which is used to measure the volume or mass of a gas or liquid is called as a
flow meter.
 Based on which industry its used in, they are called by various names such as flow
indicator, flow rate sensor, flow gauge, liquid meter etc.
 Flow meters are also used to measure rivers or streams, or any other open channels.
Most often, the highest utility from a flow meter and widest variety focus on measuring
gasses and liquid in a pipe.
 The biggest advantage of flow meters are that they improve pre scion, accuracy, and
resolution of fluid.
 The factors that one should take into consideration while selecting a flow meter are
availability of are tools, familiarity, experience, failures in the past etc.
 The mistake that people make most frequently is that they do not take into
consideration all these factors. They look for something that is inexpensive and that
leads to huge expenses in future.

3. Orientation of flow
measurement
 A clear picture of the requirements of the flow meter is the most important factor while
selecting a flow meter.
 Hence, it is advisable to invest sufficient amount of time in thoroughly evaluating the
nature and overall instillation.
 The device consists of three parts namely: primary device, transducer, transmitter.
 When the fluid passes through the primary device, the transducer is able to sense it.
 The signal which the transducer receives is later on sent to the transmitter which is
turned to a usable flow signal.

4. Components of a Flow meter

5. There are 5 various types of flow meters :
 Velocity Flow Meters
 Open channel flow meters
 Differential Pressure Flow meters
 Positive Displacement Flow meters
 Mass Flow meters
Types of flow meters

6. Velocity Flow Meters
In this type, the velocity of the stream is calculated in order to arrive at the volumetric flow
rate. When the Reynolds number of fluid is greater than 10000, they are less sensitive.
They consists of electromagnetic and sonic flow meters, paddlewheel, turbine, vortex
shedding etc.
Open channel flow meters
Flumes, weirs and v-notch are included in the measurement of liquid in open channels.
Based on the unique size and shape of the structure, these dam like structures allow for a
limited or concentrated free-flow of liquids.
Differential Pressure Flow meters
They have about 1/5 of all flow meters across the globe. It is most commonly used in the oil
and gas industry, pharma, water, mining, beverage, paper etc.

7. Positive Displacement Flow meters
Positive displacement meters also known as PD meters are utilised to measure the volume
filled with fluid, deliver it and refill it which helps to calculate the amount of fluid
transferred. They are used to measure the actual flow of liquid. The output and the volume
passing through the flow meter are directly related. They are most often used in transfer of
fluids and oils.
Mass Flow meters
They measure the force which results from the acceleration of mass hence they are most
effective in mass related processes. They consists of Coriolis mass meters and thermal
dispersion meters. The force is measured as the mass moving per unit of time in place of
the volume per unit of time.