Flow Measurement With Refracted Spread Spectrum Analysis (RSSA)

Pulsar have introduced two major innovations with the launch of Flow Pulse - firstly, of course, that the system is non-invasive, and secondly the new way that the mass of flow data is analysed. Pulsar call it Refracted Spread Spectrum Analysis (RSSA).

RSSA builds on Pulsar’s track record of excellence in acoustic digital signal processing. Pulsar’s non-contacting ultrasonic level and open channel flow measurement equipment has revolutionised the way that process and utility engineers view that technology, in large part down to the DATEM echo processing software on board. Similarly, Sludge Finder brought Pulsar’s technical expertise to bear on the challenge of accurately and reliably measuring sludge blanket interface levels

Flow Pulse is a major leap forward in flow measurement - no need to break into a pipe, or to get any civils involved, just clamp a small sensor to the outside of a pipe and get reliable, repeatable flow monitoring straight away.

Virtually no installation costs, no interruption to service, clean and simple. Flow Pulse is simply fixed in place by a band (tools required = one screwdriver). A silicone coupling pad makes sure that the Flow Pulse makes a good acoustic contact to the pipe.

Flow Pulse uses a novel spread spectrum analysis technique never before used in flow monitoring. It incorporates a radical new Digital Signal Processing (DSP) approach that gives exceptional repeatability.


Flow Pulse produces a wide ultrasonic beam that is refracted by the pipe wall, as well as reflected by suspended particles in the flowing media.

Ultrasound is fired through the pipe wall at 90 degrees to the flow via a tangentially mounted high output ceramic, then refracted at angles across the axis of the flow and subsequently reflected from bubbles, particles and vortices in all directions and at a wide range of frequencies. The wide, refracted, ultrasonic beam maximises the ultrasound energy captured from flowing particles. These multiple reflections are received back into the unit via a second high performance ceramic.

The returned signal is analysed using Flow Pulse’s Refracted Spread Spectrum Analysis (RSSA) digital signal processing platform to derive flow information. RSSA analyses and integrates the received signals over a wide frequency range, then slices them for real-time analysis and flow rate calculation.


The digital platform also offers robust performance in the repeatability of measurement, as well as the flexibility to adapt to application requirement. For example, features such as damping and response time can be easily customised to suit.

Flow Pulse operates in a flow range from as little as 0.3m/s through to 4m/s (1 - 13 ft/sec), with a minimum particle size of 100µ and concentration of 200ppm or above (the equivalent of hard water).

Pipe material can be rigid plastic, stainless steel, mild steel or cast iron. Corrugated pipe is not an issue, and, as long as the silicone pad can fill in the irregularities, light corrosion will also give a good result.

Flow Pulse provides repeatability of around ±5% (up to 350mm/14 inch pipe dia).