A water flow meter is an instrument capable of measuring the volume of water moving through a pipe. Different water flow meter technologies are available for selection depending on the water measurement applications, budgetary terms, and maintenance requirements. Each of these water flow meter technologies has a unique principle of operation, overall cost-of-ownership, and particular application benefits.

The question is which water flow metering technology should a user select for their water flow measurement applications?

There are four major types of water flow meters tech available:

  • Mechanical Water Flow Meters
  • Ultrasonic Flow Meters
  • Vortex Volumetric Flow Meters
  • Electromagnetic Flow Meters

 

Mechanical Flow Meters

Mechanical flow meters are the most common flow metering tech which obvious that its best cost-effective water flow meter available that perform flow measurement through turbine rotation with a shunt, propeller or paddle wheel design.

Principle:

Water flow is measured when water flows through a pipe with the speed which causes a piston or turbine to rotate were volumetric flow rate of water proportional to the rotational speed of turbine blades.

Disadvantages:

Mechanical water meter clogs up when exposed to contaminants and large particles that leads to bigger maintenance cost.

Without the element of speed mechanical meters can not work.

Vortex Flow Meters

As the name suggests Vortex water flow meters use vortex shedding from a sensor immersed in the flow. Like air when passing an obstacle or stream flowing around a rock produces the vortices swirls, in a vortex flow meter volumetric flow rate is measured through a sensor tab which flexes side to side when each vortex flows past, producing a frequency output proportional to the volumetric flow rate.

Multi variable vortex flow meters can measure up to five process variables with one process connection: temperature, pressure, density, mass flow, volumetric flow rate. Insertion vortex meters work well on very large pipes as they can be inserted into the flow by pressure tapping with a retractor.

Ultrasonic Flow Meters

Ultrasonic water flow meters measure the speed of water passing through the pipe using ultrasound to measure the volumetric flow. In a transit-time ultrasonic water flow meter, an ultrasonic signal is transmitted in the direction of the downstream water flow, and another signal is transmitted toward the upstream water flow, and time taken by the sonic pulse to travel from downstream to upstream is calculated to find the velocity of the water. Then the meter calculates the volumetric flow rate in the pipe using water velocity.

In addition, BTU energy measurement can be derived from the volumetric flow rate and the temperature difference between the hot and cold legs. Clamp-on ultrasonic meters can measure water from outside of the pipe by blasting pulses of sound through the pipe walls, this application flexibility and making them suitable for water flow measurements in large pipes.

Electromagnetic Flow Meters

Electromagnetic flow meters measure the speed of water passing through a pipe using an electromagnetic field to measure the volumetric flow rate of water. They use the principle of Faraday’s Law of Electromagnetic Induction, according to which water generates a voltage when it flows through a magnetic field. The more rapid the fluid flow, the more the voltage generated. The voltage produced is directly proportional to the water movement; the voltage signal is processed into the volumetric flow rate by the electronics. Since the magnetic flow meters show an intermediate accuracy, they are not suitable for custody transfer applications and cannot be used to measure pure water as there are no ions to measure.