A Smart, Cost-Effective Programmable Gas Flowmeter Retrofitted from a Glass Rotameter

Programmable gas flowmeters with remote reading and control are increasingly needed in the era of automation and AI. However, commercially available options remain expensive, hindering their adoption. We therefore developed a cost-effective programmable flowmeter as a compact device based on a low-cost glass rotameter. This system consists of a reading unit (webcam + rotameter), a control unit (development board + stepper motor-actuated valve) using an open-loop pre-calibrated step-to-flow matrix, and a terminal interface. The side-view imaging of the glass rotameter avoids occlusion of the rotor by the scale, enabling reliable rotor identification using well-established algorithms. The flow rate is derived by mapping the normalized rotor position to the scale instead of recognizing the scale markings or numerals. Two terminal configurations are offered: USB-connected (PC + MATLAB) and embedded (Raspberry Pi + Python). The USB-connected configuration uses direct serial communication between MATLAB and Arduino for stepper motor step control, ensuring fast response and good compatibility. The prototype retains manual control and direct eye reading. Experiments demonstrated strong programmability, fast response (0.2 s), high accuracy (mean error < 3%), and stable reading (fluctuation < 0.5%). This cost-effective yet programmable gas flowmeter is expected to benefit gas sensor development and accelerate automation in fluid-related fields.