Ultrasonic flowmeters

Ultrasonic flowmeters use sound waves to determine the velocity of a fluid flowing in a pipe. At no flow conditions, the frequencies of an ultrasonic wave transmitted into a pipe and its reflections from the fluid are the same. ... When the fluid moves faster, the frequency shift increases linearly. A basic analogy would be Swimming against the flow requires more power and more time than swimming with the flow. This simple fact is the basis for ultrasonic flow measurement according to the “differential transit time” method: This method uses two sensors, set opposite each other in the measuring tube. Each sensor can alternately transmit and receive ultrasonic signals, while simultaneously measuring the signal transit time. As soon as the fluid in the tube starts to flow, the signals are accelerated in the direction of flow but delayed in the opposite direction. The differential transit time, measured by the two sensors, is directly proportional to the flow rate. The Flow Volume can be calculated by multiplying it with the cross sectional area, which is obtained by using the pipe diameter and wall thickness.

Benefits

Measurement independent of pressure, density, temperature, conductivity and viscosity (for homogeneous fluids)

Free pipe cross-section, no pressure loss

No moving parts, minimum maintenance and upkeep

Long service life, no abrasion or corrosion from the fluid

In-line or clamp-on design for stationary or temporary flow measurements