Electromagnetic vs Ultrasonic Meters

We at Arad are proud of our industry-leading bulk (Octave) and residential (Sonata) ultrasonic smart water meters as well as our high-end electromagnetic water meters: Multijet Magnetic Meter and AcquaMag, from our wholly owned subsidiary WaterTech. In this blog post we explain how ultrasonic and electromagnetic water meters work and the pros and cons to consider when choosing between them.

How Electromagnetic Meters Work

Electromagnetic meters, sometimes referred to as mag meters, operate on the principal of Faraday’s Law, which states that a conductor, such as water, produces an electric current when it passes through a magnetic field. Using this principal, a mag meter is attached to a water pipe perpendicular to the water flow. As the water passes through the magnetic fields the meter measures the changes in voltage and, together with the measured velocity of the water flow, calculates the water’s volume.

How Ultrasonic Meters Work

Ultrasonic meters use sound waves to determine the water’s velocity, which is then converted into the volume that passes through the meter. There are two different methods of measuring the sound wave: time-transit and Doppler.

Time-transit meters send ultrasonic signals to two points along the pipe. Measuring the amount of time that it takes the sound wave to travel between the two points lets you determine first the velocity and then the volume of the water passing through the pipe.

Doppler meters measure ultrasonic signals that are bounced off of particles and materials in the water, such as water bubbles, to determine the volume. [2]

A Quick and Dirty Comparison between Mag Meters and Ultrasonic Meters

Here is a short breakdown of the pros and cons of the two types of meters.

 

Electromagnetic

Ultrasound

Pros

  • No moving parts
  • Almost no pressure drop
  • Accurate to +/- 0.25%
  • Available in virtually all pipe sizes up to 120”
  • Responds well to rapid changes of flow
  • The ease of installation is a key advantage of ultrasonic meters. There is virtually no down time and no need to change current piping.
  • Lower initial costs for the meters.
  • No moving parts, which cuts maintenance costs.
  • The device will not obstruct water flow.
  • Zero pressure drop.
  • Available in virtually all pipe sizes up to 200”
  • Resilient to all weather conditions and atmospheric pressure changes

Cons

  • Water must contain a minimum amount of microsiemens so that it can conduct electricity.
  • The accuracy may be affected by the air space in the pipe.
  • The price is much higher than ultrasonic meters.
  • If the water flow rate drops to below 2 feet per second then the accuracy of the meter is affected.
  • External problems of the pipes can affect the meter’s accuracy.
  • The accuracy may be affected by the air space in the pipes.
  • Unexpected particles in the water can affect the meter’s accuracy [3]

 

Final Note

While advances in the field of smart waters metering are being made around the globe, we at Arad are keeping our products at the cutting edge of development ensuring that we can provide the best possible product at the most competitive prices.

References

[1] Jeff Stryker Water Meters – Flow Sensors, 2019
[2] McCrometer, Electromagnetic and Ultrasonic Meters—A Comparison, 2019
[3] Central Station Steam Company, Ultrasonic vs Magnetic Flow Meters

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