Editorial Feature

Measuring Fluid Dynamics: Liquid Flow Sensors in Industry

Liquid flow sensors offer precise monitoring capabilities that enable industries to optimize their relevant operations. Learn about the significance of liquid flow sensors in industrial processes, the working principles, diverse applications, and their impact on commercial operations.

Splashes of oily liquid. Organic or motor oil on a white background

Image Credit: Hekla/Shutterstock.com

How do Liquid Flow Sensors Work?

Liquid flow sensors are devices that measure liquid flow rate through a system by utilizing various technologies, like electromagnetic, ultrasonic, thermal, and mechanical principles, to provide accurate and real-time data on fluid movement.

For instance, electromagnetic flow sensors utilize Faraday's law of electromagnetic induction by measuring the flow of conductive liquid via the correlation of the liquid's velocity and voltage when it flows through a magnetic field generated by the sensor.

Ultrasonic sensors, on the other hand, emit ultrasonic pulses through the liquid and measure the time it takes for the waves to travel upstream and downstream, which helps them determine the velocity of the liquid and, ultimately, the flow rate.

Similarly, thermal flow sensors are used to calculate liquid flow rate, particularly in low-flow applications, by measuring the heat transfer between a heated element and the flowing liquid. Mechanical sensors, such as paddlewheel or turbine sensors, operate based on measuring the rotation of a mechanical element in response to the fluid flow.

Applications of Liquid Flow Sensors

Liquid Flow Sensors Used in Oil and Gas Refineries

Liquid flow sensors are of critical importance in the oil and gas industry. Thermal and ultrasonic flow sensors are commonly deployed to monitor the flow rates of crude oil, refined products, and chemicals within the intricate network of oil and gas pipelines. For instance, in a 2022 study, researchers addressed the challenges of measuring phase flow rates in water-based dispersed wavy flow, a common pattern in oil-gas-water three-phase flow in petroleum production.

The study introduces a combined electrical and ultrasonic sensor system that simultaneously acquires online information. The conductance sensor estimates water fraction, the pulse-wave ultrasonic sensor calculates gas fraction by locating the gas-liquid interface, and a continuous wave ultrasonic Doppler sensor extracts the velocity of oil droplets and the gas-liquid interface.

A theoretical model based on momentum balance analyzes the acquired data to calculate phase flow rates. Dynamic experiments validated the method, demonstrating its potential for non-intrusive phase flow metering in industrial three-phase flow, particularly in water-based dispersed wavy flow patterns.

Novel Liquid Flow Sensor for Biomedical Applications

In a 2021 study on liquid flow sensors in industrial processes, researchers proposed a novel flow meter using optical fiber sensing. Unlike traditional turbine or pressure-based sensors, this method is non-intrusive, requires zero maintenance, and is resistant to clogging, making it suitable for harsh conditions. The technique involves monitoring temperature distribution along a fluid conduit by injecting pulsed heat locally. The propagation velocity of the heat downstream is used to determine the fluid’s velocity.

The study explores the potential for scaling the technique to cover sensing ranges of several tens of kilometers or miniaturization for microfluidic systems, opening avenues for biomedical applications. The findings highlight the system’s resilience in harsh conditions and its potential for real-time monitoring of various industrial processes.

Industrial Applications

Liquid flow sensors are also used in water treatment plants to ensure a precise balance of various chemicals and water flows for effective purification. Similarly, in the pharmaceutical industry, it is used to control the inflow of liquid drugs accurately for precise quantity measurements.

In food and beverage production, mechanical flow sensors, such as turbine sensors, are employed to measure the flow of ingredients accurately. For instance, in beverage bottling plants, liquid flow sensors help control the filling process, preventing underfilling or overfilling of containers.

Recent Developments

In a recent study addressing drug overdose risks in intravenous (IV) infusion, researchers developed a novel piezoresistive liquid flow sensor for real-time monitoring. The sensor features an erected polymer hair cell on a multi-layered silicon base, utilizing gold strain gauges on a piezoresistive liquid crystal polymer (LCP) membrane.

The LCP membrane sensor outperformed commercially available IV sensors, demonstrating a low threshold detection limit of 5 mL/hour. This miniaturized, biocompatible sensor can be installed inside IV tubes for in-suite online flow monitoring, offering improved sensitivity at low flow rates and potential advancements in drug administration safety in the medical industry.

The LD20 liquid flow sensor by Sensirion is a good example of such sensors used commercially. The LD20 liquid flow sensor offers precise and secure measurement of low flow rates, which is crucial in clinical applications, ensuring patient safety and optimal treatment outcomes with bidirectional flow measurement and real-time failure detection. Moreover, its cost-effective design, featuring barbed or luer lock fittings, enables easy integration into fluidic lines, while its use of inert materials ensures chemical resistance.


In conclusion, liquid flow sensors play a crucial role in optimizing industrial processes, offering precise monitoring through diverse technologies like electromagnetic, ultrasonic, thermal, and mechanical principles. Liquid flow sensors are used in several industries, such as oil and gas, medical, food and beverages.

Recent developments like piezoresistive liquid flow sensors for IV infusion safety and sensors like LD20 showcase advancements in liquid flow sensors, especially in the medical industry. With the continuous evolution of technologies, liquid flow sensors are likely to become even more prevalent, further contributing to fluid dynamics measurement in industrial processes.

See More: Customizing Liquid Flow Meters for Specific Applications

References and Further Reading

Sensirion. Liquid Flow Sensor LD20. News-Medical Life Sciences. https://www.news-medical.net/Liquid-Flow-Sensor-LD20

Lötters, J. (2005). Liquid flow sensor for nano‐and micro‐flow ranges. Sensor Review. https://doi.org/10.1108/02602280510577771

Ejeian, F., Azadi, S., Razmjou, A., Orooji, Y., Kottapalli, A., Warkiani, M. E., & Asadnia, M. (2019). Design and applications of MEMS flow sensors: A review. Sensors and Actuators A: Physical. https://doi.org/10.1016/j.sna.2019.06.020

Nouri, N. M., & Sakhavi, N. (2023). Numerical analysis of liquid flow measurement using multipath ultrasonic phased array flowmeter. Ultrasonics. https://doi.org/10.1016/j.ultras.2022.106859

Hagihghi, R., Razmjou, A., Orooji, Y., Warkiani, M. E., & Asadnia, M. (2020). A miniaturized piezoresistive flow sensor for real‐time monitoring of intravenous infusion. Journal of Biomedical Materials Research Part B: Applied Biomaterials. https://doi.org/10.1002/jbm.b.34412

Shi, X., Tan, C., Dong, F., & Escudero, J. (2022). Flow rate measurement of oil-gas-water wavy flow through a combined electrical and ultrasonic sensor. Chemical Engineering Journal. https://doi.org/10.1016/j.cej.2021.131982

Jderu, A., Soto, M. A., Enachescu, M., & Ziegler, D. (2021). Liquid flow meter by fiber-optic sensing of heat propagation. Sensors. https://doi.org/10.3390/s21020355

Sensirion Inc. (2023, June 06). Measuring Lowest Flow Rates in Medical Therapies. News-Medical. Retrieved on January 21, 2024 from https://www.news-medical.net/whitepaper/20180811/Measuring-Lowest-Flow-Rates-in-Medical-Therapies.aspx.

Disclaimer: The views expressed here are those of the author expressed in their private capacity and do not necessarily represent the views of AZoM.com Limited T/A AZoNetwork the owner and operator of this website. This disclaimer forms part of the Terms and conditions of use of this website.

Taha Khan

Written by

Taha Khan

Taha graduated from HITEC University Taxila with a Bachelors in Mechanical Engineering. During his studies, he worked on several research projects related to Mechanics of Materials, Machine Design, Heat and Mass Transfer, and Robotics. After graduating, Taha worked as a Research Executive for 2 years at an IT company (Immentia). He has also worked as a freelance content creator at Lancerhop. In the meantime, Taha did his NEBOSH IGC certification and expanded his career opportunities.  


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