Crossed-path Fluvius system in channel

Fluvius is an area velocity ultrasonic flowmeter which uses the time of flight method. An ultrasonic pulse is sent with and against flow direction. The difference in signal travelling time (time of flight) is then evaluated. Combined with water level measurement and the cross-sectional area, Fluvius accurately determines flow over its entire measuring range. Fluvius can measure in up to 8 acoustic paths, e.g. in four planes with two crossed paths each.

Multi-path systems have several advantages: 

1. Cross flows in channels and rivers may form due to conditions such as bends in the river course. Although cross flows do not influence the total flow volume, they can affect the measurement accuracy. With a crosswise arrangement of four transducers, secondary flow effects can be eliminated. 

2. When water levels in channels or rivers are changing significantly, multiple paths ensure that the flow profile is measured consistently. With rising water level, more acoustic paths are activated. This system guarantees measurement accuracy at all times.

3. A system with acoustic paths layered on top of each other in parallel planes removes the need for a timeconsuming hydrometric calibration. For these reasons, the Fluvius system is suitable for applications with large water level fluctuations, reverse flow or a vertical velocity distribution outside the theoretical normal.

The ideal sensor for a Fluvius system can be evaluated in relation to the acoustic path length and sediment load. The ultrasonic measurement signal may be damped by friction and suspended solids. Lower frequencies allow for a considerably better signal quality in applications with high solid content or wide distances between the transducers. 

For example, a path length of 200 m and a sediment load of 300 g/m3 result in the optimal sensor type TD-28/18.

The Fluvius system is composed of a wall-mounted transmitter and several transducer options depending on acoustic path lengths and sediment load.

Wall-mounted transmitter

The Fluvius transmitter incorporates all the required algorithms and software to ensure measurement accuracy and repeatability. 

The transmitter controls the measurements, calculates the flow rate and provides freely programmable current outputs, status alarms, frequency outputs and totalizer readings. The IP65 (NEMA 4X) powder-coated sheet steel housing features a 4 x 20 alphanumeric LCD. 

Fluvius uses a Windows 10 operating system. Configuration and signal analysis can be done using the integrated software packages FlowVision DB and FlowVision SA. All configuration data as well as measured and calculated data are stored in the internal data logger. 

By using TeamViewer or Ultra VNC software application you can remotely control the flowmeter as if you were sitting right in front of it.

Transducer TD-28/18, 28 kHz and TD-200/8, 200 kHz

The Fluvius sensors are mounted on the side of river, channel or conduit walls. The mounting from the side prevents aggregation of sediments on top of the sensor and enables easy installation and cleaning. Standardized sensor mounting devices are available for any kind of channel geometry like rectangular, trapezoid or natural riverbanks. The flow-optimized design protects the transducers against moving objects suspended in the flow stream. This method has proved its worth for applications in channels or rivers with high waste contents. The enclosure design also provides room for connections and protective conduits.

Pressure levelsensor

The Fluvius system may be combined with an external pressure level sensor via the analog input of the transmitter. 

A 16-bit A/D converter for analog signal outputs (4-20 mA) is integrated in the microprocessor of the sensor. This converter measures the sensor signal up to 500 times per second. 

The micro-processor electronics mathematically compensate temperature dependencies and non-linearities, resulting in high-accuracy measurement of typically 0.04 % FS and a total error band of 0.15 % FS over the entire pressure and temperature range.