NIVUS tested their new acoustic echo correlation velocimeter NivuFlow Stick in an independent tow operated by the Federal Institute of Metrology (METAS). The Swiss tow tank, was the instruments supplier first choice for the measurements. The calibration facility is accredited to ISO 17025/2017 and the tank is seeded with polyamide particles for the calibration of acoustic devices. Cross correlation sensors measure the velocity based on the ultrasound reflection principle and therefore require particles in the water for the measurement. Calibration measurements were successfully performed for velocities from 0,05 m/s up to 1,0 m/s. The obtained velocity accuracy of the NivuFlow Stick met very well the NIVUS specifications with an error limit of 0,5% of measured value (+5mm/s).

Tow tanks are worldwide used for the calibration of hydrometric measuring instruments, which measure the flow velocity of water bodies. A tow tank consists of a channel filled with water and a towing carriage on tracks which moves at controlled velocities. The instrument to be calibrated is mounted on the towing carriage and is pulled at different velocities through the still water. The velocity measured by the sensor is compared with the reference velocity of the towing carriage. With a tow tank the sensor’s measurement accuracy can be determined in a highly precise test set-up free of environmental and human errors.

The NivuFlow Stick multipoint-measurement, acoustic echo correlation velocimeter is capable of measuring the full flow velocity profile with velocities automatically measured from the bottom of the channel up to the water surface. This significantly improves measurement accuracy and means that discharge measurements can be completed in a shorter time where the meter does not have to be positioned at the different sampling depths.

More information about our NivuFlow Stick velocimeter