An Enhanced Technique for Ultrasonic Flow Metering Featuring Very Low Jitter and Offset

Abstract

This paper proposes a new, improved method for water flow metering. It applies to a transit time ultrasonic flow meter device. In principle, the flow of a given liquid in a pipe is obtained by measuring the transit times of an ultrasonic wave in the upstream and downstream directions. The difference between these times is, in theory, linearly proportional to the liquid flow velocity. However, the fainter the flow is, the smaller the transit time difference (TTD) is. This difference can be as low as a few picoseconds, which gives rise to many technical difficulties in measuring such a small time difference with a given accuracy. The proposed method relies on measuring the TTD indirectly by computing the phase difference between the steady-state parts of the received signals in the upstream and downstream directions and by using a least-square-sine-fitting technique. This reduces the effect of the jitter noise and the offset, which limit measurement precision at very low flow velocity. The obtained measurement results illustrate the robustness of the proposed method, as we measure the TTD at no-flow conditions, with a precision as low as 10 ps peak-to-peak and a TTD offset of zero, within a temperature range from room temperature to 80˝C. This allows us to reach a smaller minimum detectable flow when compared with previous techniques. The proposed method exhibits a better trade-off between measurement accuracy and system complexity. It can be completely integrated in an ASIC (application specific integrated circuit) or incorporated in a CPU-or micro-controller-based system.

Multi-Angle Liquid Flow Measurement Using Ultrasonic Linear Array Transducer

“…Considering the incidence and reflective angles, the matching receiver elements for the transmitter elements were calculated (e.g., matching elements for incidence angle (θi) of 20.13° are 90 and 39 for the downstream and upstream, respectively). Most of the transmit-time ultrasonic flowmeters performed time estimation using the conventional zero-crossing approach, which detects the zero-crossing time of the received ultrasonic signals [5,25]. Afterward, the zero-crossing time difference between the upstream and downstream was measured.…”

“…Flowmeters [1] have been utilized for liquid and gas flow rate measurements in industrial and medical fields. There are several types of liquid flowmeters, such as turbine [1], vortex [2], electromagnetic [3,4], and ultrasonic flowmeters [1,5]. The ultrasonic flowmeter can be applied for either invasive or non-invasive measurements with relatively easy installation [6,7].…”

Liquid Flow Measurement Using Silicone Polymer Wedge Clamp-On Ultrasonic Transducers

“…The time difference between the upstream and downstream signals can be quite small (< ns) at low flow rates [3]. To measure t  accurately, a cross-correlation method is used to calculate the time delay between the downstream and upstream ultrasonic signals [18].…”

“…There are several alternative flow meter technologies and each one has a unique principle of operation, overall cost-of-ownership, and specific application benefits [2]. Compared with other flow meters [2][3][4][5], clamp-on ultrasonic transducers (CUTs) exhibit significant operational and economic advantages such as inexpensive to install and maintain and have a broader flow rate measurement range [6].…”

Design and characterization of immersion ultrasonic transducers for pulsed regime applications

“…Concerning the utilization of broad-band transducers, which in general use soft piezo materials, a wide range of potential industrial applications exist. Non-destructive testing, flow metering [1][2][3][4] , material evaluation [5] and medical diagnosis [6,7] are the major application areas. Furthermore, ultrasonic transducers are widely used for the measurement of diverse quantities, such as detection of interfacial position on two-phase (gas-liquid) flows [8] , short range vehicle detection in smart cars [9] , or measurement of thickness, position, or fluid properties such as density, viscosity, etc.…”