• • • SENSORS & SENSING SYSTEMS • • •
This non-intrusive measurement technique works with clean liquids and gases, has no effect on the flow medium itself and scales across various pipe diameters. Crucially, it also eliminates the drawbacks of turbine-based mechanical flow sensors. The absence of moving parts inside the flow medium means that the sensor offers a practically unlimited operating lifespan, and can also measure extremely slow flow speeds. Implementation of this method of flow sensing calls for extremely accurate measurement of the small-time differences between downstream and upstream sound transmission, a phenomenon measured in picoseconds.
In fact, the entire time signal-processing function may be implemented by an ultrasonic flow converter IC from ScioSense. This highly integrated device measures the time difference between the return signals, and converts the measurements to a flow rate and accumulated volume data for any given pipe diameter.
Key design considerations in
ultrasonic flow metering To integrate an ultrasonic flow converter (UFC) into a flow sensor system, the designer has to take account of various considerations which affect the operation of the technology. These include: • The transducer mounting geometry • The acoustic properties of the pipe material: metals, plastics and composite pipes each have different acoustic impedances and attenuation characteristics. Wall thickness, surface finish, and coatings can reflect or absorb acoustic energy. The acoustic path must also account for refraction at material boundaries.
• Temperature variation: sound velocity in fluids varies significantly with temperature. For instance, the speed of sound in water varies by approximately 0.6 per cent/degrees celsius.
Off-the-shelf modules provide
The second problem with turbines is catastrophic failure: the turbine is a moving part, and so can become corroded or broken. Reliability is a key issue for users of flow sensors: mechanical flow sensors suffer from wear and tear which limit their operating lifespan.
Ultrasonic flow sensing technology eliminates moving parts
If the problem is the presence of a mechanical component in the flow to be measured, then the solution is to measure flow contactlessly. This can be accomplished by ultrasonic sensing technology. Ultrasonic flow sensors measure fluid flow rate by transmitting sound waves through the flowing medium via paired transducers positioned diagonally across the pipe. One transducer sends ultrasonic pulses downstream while the other sends them upstream. The flowing fluid affects propagation speed: downstream pulses travel faster (aided by the flow) while upstream pulses travel more slowly (impeded by the flow). Flow velocity is directly proportional to the difference in transit times between these paths.
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ready-made solution Specialists in flow measurement system integration, such as water utility meter manufacturers, maintain internal design expertise to enable the integration of a UFC into a custom flow sensor assembly, taking account of the factors listed above.
But the wider application of flow sensing has value in a broad range of other types of equipment. Examples include: Coffee brewing machines, beverage dispensers, water purifiers, water heaters, boilers and heat pumps, swimming pool cleaners, smart sanitary equipment and toilets, floor cleaners, irrigation systems, cooling machines, smart water coolers, industrial process control systems and filters and livestock feeding equipment.
In these applications, flow sensing is a peripheral rather than a primary function, and so here OEMs typically prefer a ready-made, off-the- shelf ultrasonic flow sensing solution which dramatically reduces design time and effort and accelerates time to market.
Complete ultrasonic flow sensor modules meet this market need. ScioSense is a pioneer in this market, offering first the UFM-01 and, in 2025, launching an improved version, the UFM-02. The advantage of a modular solution is that it is
extremely easy to integrate into end equipment designs. In the case of the UFM-02, for instance, the module is available in two thread sizes , 0.5” and 1”, each provided in either a BSPP (British Standard Pipe Parallel) or NPS (American National Pipe Straight) format. Two thread sizes, 3/8” and1.5”, will be available soon. The smallest thread size handles a maximum flow rate of 20l per minute, and the largest, up to 450l per minute. The module is highly sensitive to slow liquid flows, allowing the sensor to accurately detect leakage. In its smallest, 3/8” thread size, the UFM- 02 can measure flows as slow as 0.03l per minute. The UFM-02 is also easy to interface to any microcontroller or PLC. The module is available with a choice of two cable connections: A four-wire pulse interface cable providing a simple output signal with up to 450 pulses per litre, and a 10-wire SPI cable which provides digital data including total volume of liquid flow in cubic meters, filtered flow rate in liters/hour, and a measurement of the liquid’s temperature
An important development in the second-generation UFM-02 module is its power consumption, which is substantially lower than in the UFM-01. Average operating current has been reduced to 50µA, low enough to enable applications to run for years on a standard primary battery.
The introduction of this latest module means that a drop-in solution for ultrasonic flow sensing can now be implemented in applications which cannot easily be connected to a mains or other external power supply and so rely on battery power.
Module manufacturer with a long heritage in ultrasonic flow sensing
Ultrasonic flow sensing provides a reliable, accurate and sensitive alternative to traditional mechanical flow sensing. By using a modular off- the-shelf sensing assembly, OEMs can take advantage of these qualities of ultrasonic technology in a solution which is easy to integrate into an electronics system.
Designers who evaluate the latest UFM-02 module can also take confidence from the long heritage of ScioSense, a company which introduced its first ultrasonic flow converter IC more than 25 years ago, and which can offer customers deep expertise in every aspect of the implementation of ultrasonic technology for flow measurement.
https://www.sciosense.com ELECTRICAL ENGINEERING • MAY 2026 13
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