The Neptune Blog

Metering Technology: Ultrasonic vs. Electromagnetic

Mechanical water meters have been in use for over a century, relying on a straightforward mechanism: the flow of water displaces a measuring element, which rotates gears, enabling a dial to record the volume of water passing through the meter. While they have been reliable technology for meter reading for decades, the industry is transitioning towards more advanced metering technologies referred to as ‘solid state’ metering, meaning they have no moving parts.

Solid state technologies use ultrasonic waves or electromagnetic fields. While they tend to have an initially higher cost than mechanical meters, solid state technologies’ impressive advantages more than justify the investment over the life of the meter. Without moving parts, the meter avoids mechanical friction, which wears down a mechanical meter’s measurement components, causing a loss of accuracy and, as a result, a loss of revenue for utilities. Solid state meters maintain their accuracy over the life of the meter, providing peace of mind for customer billing accuracy. Sustained accuracy also removes the need for field maintenance by eliminating costly truck rolls and down time from field testing.

Solid State Meter Technologies

While there are a variety of different technologies on the market, we’ll focus on the primary two: electromagnetic and ultrasonic.

Electromagnetic

Electromagnetic, or mag meters, work by sending a magnetic field through the water flow, generating a voltage that the meter can pick up and derive the water flow rate. But because water isn’t very conductive, these types of meters are most effective with higher flow rates. The lower the flow gets, the more it appears as background noise.

Not only are electromagnetic meters less sensitive in low flows, but they also require a significant amount of battery power. Generating magnetic fields strong enough to detect water flow requires a lot of power, which in turn forces battery-powered mag meters to resort to low sampling rates to conserve battery life.  This typically results in measurement accuracy in dynamic flow conditions, as well as poor low flow accuracy. For more detail on sample rates, visit our blog here. If a mag meter has the ability to be connected to mains power, they can be very effective in mid to high flow applications. A downside is they are susceptible to accuracy degradation over time due to corrosion of the electrodes used to create the magnetic field, which introduces a lot more signal noise making it harder to trust the data coming from the meter.

Ultrasonic

Ultrasonic meters, the technology that Neptune has chosen for its MACH 10 meters, operate by transmitting sound waves through the water and measure the time it takes for that sound wave to bounce back. The faster the flow, the longer it takes the wave to be registered.

Inside the meter body are components that produce soundwaves and matching mirrors, allowing water to be measured in both directions. This means the meter can be mounted in a variety of orientations, it is largely unaffected by small particles or bubbles and is capable of measuring back flow. Unlike the magnetic field of mag meters, producing ultrasonic waves takes very little power, which allows ultrasonic meters to have exceptional battery life, even when measuring flow several times per second. For example, mag meters sample as infrequently as twice a minute, but the MACH 10 ultrasonic meter samples at four times per second, meaning they are measuring water more frequently, leading to more accurate results. This also allows them to maintain a high level of detection across a wide range of flow rates, from ultra low-flow to very high flow rates, without compromising battery life.

On Neptune’s MACH 10 meters, we expect batteries to last up to 20 years due to the advanced low-voltage battery technology we’ve implemented. Our batteries have high energy density, long shelf life, and ability to operate in extreme temperatures.

Conclusion

Advanced metering technology is designed to help utilities provide safe, clean drinking water to their customers while accurately measuring water use. While mag meters excel in specialized laboratory and industrial applications, ultrasonic meters are more practical for utility use, allowing them to better account for and bill accurately for water usage and reduce maintenance costs. Investing in the right technology for your utility’s goals will help you to future-proof your operations and maximize your revenue year after year.

Learn more

For more details on these advanced technologies please see our white paper.

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