How Ultrasonic Flow Meters and IoT Connectivity Combine for Smart Metering Systems

July 10, 2019 by Gary Elinoff

Smart cities are exploiting the power of the Internet of Things to prevent wasting water.

Smart cities are exploiting the power of the Internet of Things to prevent wasting water.

Smart cities have been described as urban areas that exploit digital technology to make more efficient use of all resources. Aside from energy, perhaps the most important asset that must be managed is water. To manage water, the first thing to be known is how much of it leaves one point, and then how much of it arrives to where it’s supposed to go next.

Water metering, the calculation of how much water has passed through a section of pipe, has been traditionally accomplished with mechanical flow meters. Large, cumbersome, and unwieldy, these devices are notoriously inaccurate and prone to mechanical breakdown.

Here, we'll go over the concepts behind flow meters, some example hardware, and consider how connectivity has changed utilities measuring in the IoT. We'll also highlight a brand new example of the smart metering data being transmitted via the NB-IoT for utilities management in China.

The New Building Blocks: Sonic Water Metering

The last few years have seen the development of electronically-based water flow meters. The most common type is based on the principle of measuring sound, a concept I describe more fully in a subsection of my article on time-to-digital converters.

In the illustration below, “A” and “B” are sound transducers, both capable of sending and receiving sounds. One sends and the other receives, and the time is recorded, then the sequence is reversed.


An example diagram of a water flowmeter. Image from Maxim integrated


Because the sound is moving through the flowing water, the sound wave traveling in the direction of the flow moves faster. In the reverse direction, the soundwave moving against the flow is slowed down. If you imagine a crew team rowing a boat in a river, the rowers will move faster going downriver than they would going upriver.

These measured times are subtracted, which yields the velocity of the water. Combined with the pipe’s diameter, the onboard electronic intelligence can determine the volume of water transversing the pipe per unit of time.

There are many devices using this principle, and other methods to completely eliminate moving parts in water flow meters. An example is the SLF3x from Sensirion, shown below.


The SLF3x. Image from Sensirion


Notice that, unlike a classical mechanical sensor, there is no visible readout; rather, there is an electrical connection instead of a visual readout. The SLF3x encodes its measurements into digital signals, the I2C protocol, specifically. This is common in modern, electronically-based flow sensors, and it is a critical point for a number of reasons.


An Emphasis on Connectivity: IoT Smart Metering

The rapid adaptation of the IoT (internet of things) has been accompanied by much progress in wireless connectivity. As such, the problems associated wired connections in damp environments without temperature controls can be completely avoided. 

This can be achieved by coupling flow meters with devices such as the SARA-R510M, which I describe in my article on a 5G module by u-blox. This specific device utilizes NB-IoT (narrowband internet of things) radio technology for the lowest possible power consumption. Most importantly, it will also be able to exploit 5G when its availability becomes more widespread.


The SARA-R5 LTE-M and NB-IoT module. Image from u-blox


With old-school mechanical sensors, to find out how much water has passed through a given point, a human meter reader has to venture into whatever remote corner that the meter is installed in and note the value. This takes time and it costs money. With devices like the SLF3x, the electrical signal is transmitted to a central point where it can be more conveniently accessed.

With multiple sensors at various spots along the waterflow, comparisons can be made. If they don’t match expected measurements, a leak will be suspected that can then be investigated and fixed before it gets worse. This, again, saves time and money.

The communication with SLF3x is bi-directional. This means that, if desired, readings can be made only periodically. This saves power, which means that battery replacement will be an extremely infrequent requirement, an important plus if the device is located in an inconveniently accessed location.

Real World Smart Metering Initiatives: China Water Utilities’ Platform

Rock-solid, real-time measurement of how much water flows through successive electronically based water flow meters can now be transmitted to a central location. As mentioned above, subtracting the measurement from the former yields a measurement of how much is lost through a leak. This is the main modus of the China Water Utilities’ Platform, a collaboration affected between ams, Qingdao iESLab Electronic Co., Ltd. and Jiangxi Water Group Co., Ltd.

The project, announced this week, involves the use of ultrasonic water metering and NB-IoT technologies based on Alibaba Cloud. Jiangxi will employ water meter designs based on ams ultrasonic flow measurement solutions connected to the utility via an NB-IoT wireless network.

The measuring device employed is iESLabs’ IA-UWM-2-GP30-DN20 ultrasonic flow sensing module. The TDC-GP30 ultrasonic flow sensor chip from ams is one of the module’s major components.


The IA-UWM-2-GP30-DN20 ultrasonic flow sensing module from Chinese manufacturer iESLabs features the ams TDC-GP30 IC. Image from ams.


An aim of the project is a demonstration of the “big data dividend” possibilities inherent in ultrasonic water metering. It is expected that the real-time, high-precision data obtained will help Jiangxi to better understand customer usage profiles in order to dynamically manage its water distribution infrastructure and services to around 10 million households.

Most importantly, it is expected that water waste reduction can be achieved by precisely locating leaks, and enabling management to rapidly effect repairs.

Big Data Payoffs for Future Utilities Systems

Real-time data from millions of locations will be amalgamated using cellular networks and delivered to a virtual data center provided by Alibaba Cloud. The Big Data can then be mined via data analytics. 

Jiangxi will gain invaluable knowledge of the locations, the timing and the rates of water consumption. Small problems can be flagged before they become big problems. And, with better knowledge of conditions on the ground, the company will be able to better job of deploying resources to needs now much more clearly defined.