OTT SLD fixed acoustic Doppler flowmeter

Technical characteristics

Can be used for online measurement of rivers or open channels

Especially optimized for high sediment content and flood conditions

High-precision flow measurement

Stable and reliable readings

Index flow method to calculate flow

Simultaneously measure the flow velocity in the x and y directions to calculate the flow direction

Patented water level measurement technology, high-precision water level measurement

Integrated temperature probe for water temperature monitoring and sound velocity compensation

Integrated forward tilt and roll sensors for easy installation and adjustment

Small size, easy to install, and little impact on flow.

Easy operation and management

Random software provides comprehensive QA / QC and installation quality inspection to avoid installation problems

Comes with the law software, which can be carried out in three ways: hydraulic model, velocity distribution and known flow

RS485, SDI12 communication protocol, support long-distance data transmission

 

Measuring principle

Flow rate measurement:

OTT SLD uses ultrasonic Doppler principle to measure flow rate. The instrument emits two ultrasonic waves in the horizontal direction. The ultrasonic waves will reflect the particles in the water, and there is a certain offset between the frequency F2 of the reflected wave and the original sound wave frequency F1. The magnitude of this offset is different from the sound source and the particles. Relative speed. Using the measured reflected wave frequency and the transmitted wave frequency, the movement speed of the reflecting particles can be obtained, and then the movement speed of a large number of particles can be combined to calculate the water flow velocity.

The angle between the two ultrasonic waves is 135 degrees, and the sound beams are respectively 67.5 degrees upstream and downstream of the cross section. Using the principle of speed synthesis, the velocity in the x direction parallel to the main direction of the flow and the y direction perpendicular to the main direction of the flow are obtained. Flow rate.

According to the difference in ultrasonic transmission distance, SLD divides the cross-section into a maximum of 9 measurement units, and measures the average flow velocity among the 9 measurement units respectively. Flow rate measurement accuracy can reach 1%. According to the actual width of the section, random software can be used to adjust the length of the blind zone and the length of a single measurement unit.

Water level measurement:

 

The built-in ultrasonic sensor of OTT SLD is used to measure the water level. The instrument comes with a vertically upward ultrasonic probe to transmit ultrasonic waves to the water surface. The time difference between the transmission and reception of ultrasonic waves is used to calculate the height of the water surface. In order to avoid the impact of water surface fluctuations and floating objects on the water surface, the instrument has a built-in pressure sensor for deep calibration. The water level measurement is valid only when the difference between the water level measured by the ultrasonic probe and the water level measured by the pressure probe is within a certain range. In this way, the exact position of the actual water surface is determined as the basis for the flow calculation.

This technology is a patented technology, not affected by outside air pressure, and the accuracy of water level measurement is up to 3mm.

 

Application range

OTT SLD is suitable for online monitoring of small and medium-sized natural rivers, artificial channels and other flows.

It can be combined with power supply, data recorder, and communication module to serve as a small flow online monitoring station.

Installation location requirements: long and straight river channel, water depth to river width ratio is about 1:10, no sudden change of river bed and river bank, no backflow.