Development of a Low-Cost Ultrasound Flow Sensor
OPEN ACCESS
Loading...
Author / Producer
Date
2026-01
Publication Type
Master Thesis
ETH Bibliography
yes
Citations
Altmetric
OPEN ACCESS
Data
Rights / License
Abstract
Accurate monitoring of emission reduction projects is essential to ensure the environmental integrity of carbon crediting mechanisms established under the Paris Agreement. In biodigester-based clean cooking projects, monitoring is often based on survey data, which is prone to systematic overestimation and may lead to over-crediting. Direct measurement of biodigester usage through low-cost sensing offers a promising alternative; however, existing gas flow and composition sensors are typically too expensive for large-scale deployment in decentralized settings.
This thesis presents the design, implementation, and evaluation of a low-cost transit-time ultrasonic flow meter intended for biogas applications. The proposed sensor measures volumetric flow rate and estimates gas composition by combining bidirectional ultrasonic time-of-flight. The system integrates commercially available components on a custom printed circuit board and is calibrated using controlled air and CH4–CO2 gas mixtures representative of field conditions.
Experimental results demonstrate that, for air, the sensor achieves a mean relative error below 3 % over a flow range of 2–10 L min−1. For biogas-like mixtures with methane concentrations between 70 % and 100 %, gas composition can be estimated with a mean relative error below 1 %, while volumetric flow rate errors increase substantially due to ultrasonic signal attenuation in CO2-rich environments. At methane concentrations below 70 %, reliable measurements are not achievable with the adopted architecture. The total estimated production cost of the prototype is approximately 36 CHF, significantly lower than that of commercially available ultrasonic flow meters.
The results highlight both the potential and the limitations of low-cost transit-time ultrasonic sensing for biogas monitoring. While the proposed sensor is suitable for applications involving high methane concentrations, extending its operational range to CO2-rich mixtures will require more advanced signal acquisition and processing techniques. Future work should therefore focus on ADC-based ultrasonic measurement approaches that offer improved robustness under low signal-to-noise conditions
Permanent link
Publication status
published
External links
Editor
Contributors
Book title
Journal / series
Volume
Pages / Article No.
Publisher
ETH Zurich
Event
Edition / version
Methods
Software
Geographic location
Date collected
Date created
Subject
Organisational unit
09746 - Tilley, Elizabeth / Tilley, Elizabeth