# Beam Drift Mitigation and Wide-Range Measurement in a Miniaturized Ultrasonic Gas Flowmeter

## TL;DR

This paper introduces a miniaturized gas flowmeter that improves measurement accuracy and range by reducing acoustic beam drift.

## Contribution

A novel miniaturized ultrasonic gas flowmeter design with a non-axisymmetric conical cavity to mitigate beam drift and enhance measurement range.

## Key findings

- The design achieves a 7.4 dB transmission gain and a 29.1° half-power beamwidth.
- The flowmeter demonstrates sound pressure attenuation of 0.72 dB at 18.74 m/s.
- It meets Class 1.5 accuracy standards with indication errors within ±2% and ±1.5%.

## Abstract

To mitigate acoustic beam drift, which degrades the signal-to-noise ratio (SNR) and limits the measurement range in ultrasonic gas flowmeters (USFMs), we present a miniaturized transit-time USFM that integrates a single piezoelectric micromachined ultrasonic transducer (PMUT) with a non-axisymmetric conical cavity. This design increases acoustic transmission gain and produces anisotropic directivity across orthogonal radiation planes, thereby broadening acoustic coverage along the flow direction and reducing beam steering. With an optimized cavity angle combination of (50°, 70°), the system achieves a 7.4 dB transmission gain and a half-power beamwidth (HPBW) of 29.1°. Experimental validation demonstrates a sound pressure attenuation of only 0.72 dB at 18.74 m/s. Within the 0.06–12 m3/h flow range, the USFM exhibits indication errors of ±2% (<1 m3/h) and ±1.5% (≥1 m3/h), with repeatability below 0.5%. The performance meets the Class 1.5 accuracy standard specified in CJ/T 477-2015, offering an innovative solution for wide-range miniaturized gas flow measurement.