Ultrasonic Smart Water Meters

Ultrasonic water meters work by using sound waves to measure the flow of water. Ultrasonics involves sound waves of frequencies greater than the upper limit of the audible range for humans—that is, greater than about 20 kilohertz. An ultrasonic transducer is a device used to convert some other type of energy into an ultrasonic vibration. Ultrasonic flow meters work by transmitting ultrasonic waves through the fluid and measuring the time it takes for the waves to travel between transducers.

Types of Ultrasonic Flow Meters

• Transit-Time Flow Meters: These meters measure the time difference between ultrasonic pulses traveling with and against the flow direction. They are suitable for clean liquids.
• Doppler Flow Meters: These meters use the Doppler effect to measure the frequency shift of ultrasonic waves reflected off particles or bubbles in the fluid. They are ideal for "dirty" liquids like wastewater or slurries.

Principle of Ultrasonic Measurement

1. Transit-Time Flow Meters

The difference in transit time between waves traveling with and against the flow is used to calculate the fluid velocity and, consequently, the flow rate.

Ultrasonic flow transducer is used as one of the core elements of ultrasonic flow meters. This uses transit time principle, whereby an ultrasonic signal is transmitted from one transducer to another through the f low. Both upstream and downstream measurements are done, and it varies depending on the flow.

When the flow is zero, the time for the signal to get from T1 to T2 is the same as that required to get from T2 to T1. When there is flow, the effect is to boost the speed of the signal in the downstream direction, while decreasing it in the upstream direction. The flowing velocity (Vf) can be determined by the following equation:

Vf =Kdt/TL

Where K is a calibration factor for the volume and time units used, dt is the time differential between upstream and downstream transit times, and TL is the zero-flow transit time. Theoretically, transit-time ultrasonic meters can be very accurate.

2. Doppler Flow Meters

Doppler flow meters measure the flow rate of fluids by utilizing the Doppler effect. Doppler effect in physics is defined as the increase (or decrease) in the frequency of waves as the source and observer move towards (or away from) each other. In the context of Doppler flow meters, it refers to the change in frequency of ultrasonic waves as they are reflected off particles or bubbles in the fluid.

Working Principle

There are two ultrasonic transducers, one acting as transmitter and the other as a receiver. The waves sent by the transmitter encounters particles or bubbles suspended in the liquid. These are reflected towards the receiver. If the particles are moving with the fluid flow, the reflected waves experience a change in frequency proportional to the velocity of the fluid. By analysing this shift with respect to the transmitted frequency, the meter determines the velocity of the fluid. This can then be used to calculate the volumetric flow rate.

Limitations

• Dependent on Particles/Bubbles: Requires the presence of particles or bubbles for accurate measurement.
• Accuracy: May be affected by the homogeneity and consistency of the fluid being measured.

Components of an Ultrasonic Smart Water Meter

Smart Water Meters use transit time principle to measure water and provide real time information on usage and leaks without any hassle of manually reading the meters.

1. Transducers Ultrasonic flow transducer is used as one of the core elements of ultrasonic flow meters. These transmit ultrasonic signals is through the flow.
2. Time to Digital Converter Time to digital converter is used to measure a time interval and convert it to a digital or binary output. TDCs are used to determine the time interval between two signal pulses (known as start and stop pulse). Measurement is started and stopped when the rising or falling edge of a signal pulse crosses a set threshold. It is used for flow by measuring the time difference between ultrasound pulses that travel through the flow and arrive at different times depending on the flow speed and direction.
3. Gateway: A GSM/Wi-Fi gateway transmits the data from the sensor/meter module to the cloud servers.
4. Cloud and UX: Cloud computing helps access data storage and computing power without the hassle of having to manage your own server. or the user interface that accesses and displays the data in various client systems, like phone app and desktop app.

Why Ultrasonic Smart Water Meters?

1. No moving parts, so no wear and tear.
2. Smart water meters have remote reading capabilities. This makes data collection easy, and any abnormal usage is reported in real-time. Software tools can be created to more effectively manage the resources utilizing these real time and accurate data.
3. High accuracy.