Installation and construction of OTT SLD fixed ultrasonic Doppler flowmeter

1、 Introduction to OTT SLD

1. Introduction

OTT SLD is an ultrasonic Doppler current profiler used to continuously monitor the flow velocity and water level of rivers and open channels. This product ensures reliable flow velocity measurement results even in flood situations with high suspended solids. The ultrasonic water level monitoring technology of this product has been granted a patent.

OTT SLD monitors water flow by injecting two horizontal ultrasonic rays, with up to nine monitoring units.

Its overall design reduces the construction work required for installation in rivers, while making the entire installation process more economical and convenient. Low energy consumption design that can be powered by solar energy. Combined with data loggers and wireless communication systems, it can serve as an online river monitoring system for real-time automatic remote monitoring of river flow velocity and volume.

2. Technical features

It can be used in rivers or open channels, especially optimized for high sediment content and flood situations.

High precision flow measurement.

Simultaneously measuring the flow velocity in both the x and y directions can calculate the flow direction

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

Equipped with ship monitoring and filtering functions, suitable for online flow monitoring of navigable rivers

Integrated temperature probe that can simultaneously monitor water temperature.

Integrated tilt probe for easy adjustment.

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

Random software provides comprehensive installation quality inspection to avoid installation problems

Equipped with calibration software, it can be calibrated through three methods: hydraulic model, velocity distribution, and known flow rate. From initial installation to normal application after formal calibration work is completed, it can provide reliable flow data.

The instrument has built-in calibration results and flow calculation, which can automatically select the corresponding calibration coefficient and cross-sectional area data based on the measured water level for flow calculation. It can directly output flow results and cumulative flow total without the need for data acquisition instruments or staff to perform secondary calculations in the later stage

RS485 and SDI12 communication protocols support long-distance data transmission, with a length of up to 1000 meters.

3. OTT SLD performance indicators

Current Speed:

Measurement principle: Use two horizontal ultrasonic waves to measure through the Doppler principle

Range: ± 10 m/s

Accuracy: 1% or ± 0% of the reading 5 cm/s

Ultrasonic frequency: 600 KHz, 1 MHz, 2 MHz

Ultrasonic diffusion angle: 2.0 degrees (600KHz), 2.3 degrees (1MHz), 1.8 degrees (2MHz)

Ultrasonic transmission range: typical 80m (600KHz), 25m (1MHz), 10m (2MHz)

***Small blind spots: 0.5m (600KHz), 0.3m (1MHz), 0.1m (2MHz)

***Large blind spots: 30m (600KHz), 15m (1MHz), 8m (2MHz)

***Small measurement unit size: 2m (600KHz), 1m (1MHz), 0.2m (2MHz)

***Large measurement unit size: 10m (600KHz), 4m (1MHz), 2m (2MHz)

Number of measurement units: 9

Horizontal ultrasonic angle: 135 degrees

water level

Ultrasonic water level range: 0.15-10 meters

Accuracy: 3mm

temperature

Range: -4 to 30 degrees

Accuracy: 0.1 degrees

size

Length: 45-52.2 cm (depending on beam frequency)

Diameter: 7.5 cm (cylindrical)

Weight: 7 kg

Power supply: 9-16 V DC

Average power consumption: 50-500 mW (affected by measurement cycle)

Interface: RS232, RS485 or SDI12

Memory: 2M expandable to 78M

Installation method: horizontal or vertical

2、 OTT SLD on-site installation plan

1. Requirements for selecting installation location

The installation location of OTT SLD should be chosen in an area where the river flow is relatively stable. The ideal installation point should be located within 50-100 meters upstream and downstream of the river, and should be relatively straight, avoiding river bends, branching entrances and exits, areas with lush underwater vegetation, or areas obstructed by reefs as much as possible. The specific requirements are as follows:

1) The measurement area should be as straight as possible, and the river width should remain as constant as possible (without sudden widening or narrowing).

2) Note that there should be no significant changes in the riverbed near the installation location of the probe.

3) The slope of the river remains unchanged and is parallel to the spillway.

4) The roughness of the bottom bed should be kept constant.

5) Try to avoid static water, backflow, and strong fluctuations.

The installation height of OTTSLD flowmeter in water should be moderate to ensure that ultrasonic waves are not reflected back from the water surface or bottom as much as possible (as shown in the figure below). The transmission range of sound waves should be smaller than the width of the river to avoid any impact on the measurement caused by solid walls on the opposite bank. It is generally recommended that the aspect ratio of the riverbed be around 10:1, and ultrasonic coverage of 30% -80% of the river width is sufficient.

2. Introduction to the installation and fixing methods of OTT SLD

Due to the need to install the OTT SLD flowmeter in the field for a long time and immerse it in water, the sturdy reliability and long-term durability of the instrument installation bracket must be considered. In the actual installation process, due to varying on-site conditions, it is necessary to choose a suitable installation plan according to local conditions as much as possible to carry out the fixed installation of the current meter. For rivers with significant changes in water level throughout the year, sliding rail installation should be adopted as much as possible to adjust the position of instruments according to water level changes.

In addition to being sturdy and durable, the installation plan also needs to consider the ease of installation, debugging, and later maintenance.

According to the inclination of the river bank wall, it can be divided into two types: inclined bank wall and vertical bank wall. In natural rivers and artificial trapezoidal canals, inclined bank walls belong to two types; Artificial U-shaped channels and rectangular channels generally belong to vertical shorelines. The following will introduce the installation methods for response from these two types separately.

1) Installation of inclined shoreline

In some natural rivers and artificial trapezoidal channels, there is a certain inclination angle on the bank wall of the river or channel. If the water level of the river changes greatly, a sliding rail can be fixed along the inclined bank wall to fix the SLD flowmeter on the tray. The tray is placed on the sliding rail, and the installation height of the instrument in the water can be easily adjusted by moving the tray up and down with a hoist. The fixed installation of the slide rail depends on the soil conditions of the shore wall. If the shore wall is a hard surface made of stone or cement, the slide rail can be fixed to the shore wall surface with fixing bolts (as shown in Figure 1); If the shore wall is a non hard surface of natural river channel mud, a whole or partial cement pile must be installed near the installation site of the shore wall slide rail to fix the installation slide rail (as shown in Figure 2).

If the water level of the river does not change much throughout the year, a cement pile platform can be built at a depth of 0.6, and the SLD flowmeter can be directly fixed on the cement pile platform (as shown in Figure 3).

Figure 2

Figure 3

On site installation legend:

2) Installation of vertical shoreline

Rivers with vertical bank walls are usually manually excavated channels, and most of them have hard solidified river walls. In this case, the installation basically only requires fixing bolts on the river wall to install sliding rails or fixed brackets on the bank wall. If the water level changes greatly, it is necessary to use lifting ropes to move the tray or fixed bracket up and down. If the water level changes slightly in normal years, a long-term fixed installation form can be used. The schematic diagram is as follows:

On site installation legend:

3. Installation of RTU and solar power supply system

Due to the lack of mains power supply at the field installation site, it is recommended to use a combination of solar panels and batteries to power the SLD current meter. Based on the power consumption of the SLD and the selected data acquisition and transmission equipment, select solar panels of appropriate power and storage batteries of appropriate capacity. The average current measurement power consumption of SLD is 50-500mW (depending on the sampling frequency), and data acquisition and transmission equipment also needs to consider power consumption issues. While ensuring functional applications, low-power devices should be selected as much as possible. Based on the lighting and surrounding obstruction conditions on site, the solar panels are installed at a location and height with sufficient sunlight through support poles. The solar charging controller, battery, data acquisition communication equipment, etc. need to be installed in a waterproof box, and then the waterproof box is fixedly installed on the shore or near the solar support poles.

On site installation legend: