Ultrasonic Flowmeters

Ultrasonic Flowmeters

Ultrasonic flowmeters measure flow using acoustic signals transmitted through a fluid. In the differential transit-time method, two transducers alternately send and receive ultrasonic pulses along a defined path. Flow accelerates the signal in the direction of travel and delays it against the flow; the measured transit-time difference is proportional to flow velocity and therefore to volumetric flow.

Ultrasonic technology covers a wide variety of gases and liquids and is not dependent on electrical conductivity. Inline ultrasonic meters are typically selected where traceable, guaranteed accuracy is required, supported by factory calibration and a defined metrological envelope. Clamp-on ultrasonic meters mount externally on the pipe wall, enabling retrofits and temporary measurements without process interruption or pipe penetration.

A free pipe cross-section produces essentially no pressure loss and eliminates moving parts that can wear, foul, or plug. This supports long service life and low maintenance, and avoids corrosion or abrasion mechanisms that can affect intrusive sensors. For homogeneous fluids, measurement is largely independent of pressure, density, temperature, conductivity, and viscosity, reducing the need for extensive compensation.

Typical applications include water and wastewater distribution, chemical and petrochemical services, utility flows, and large-diameter transmission pipelines. Clamp-on meters are frequently used for energy audits, balancing, and verification of existing instrumentation, and for aggressive or high-pressure fluids where noninvasive installation reduces material compatibility risk. Inline ultrasonic meters are used where specified uncertainty and traceable calibration are required for accounting, custody transfer, or contractual performance guarantees.

Engineering considerations include pipe material and condition, sound path alignment, the presence of entrained gas or solids, and the degree of flow profile distortion. Straight-run requirements are often shorter than with restrictive primary elements, but installation quality remains a primary driver of achievable uncertainty. Selecting clamp-on versus inline designs is typically driven by required accuracy, allowable intervention, and whether the measurement point is temporary or permanent.

Instrumentation and Controls., an exclusive authorized representative of sales and service for Endress+Hauser.