Ultrasonic Doppler Flow Velocity Meter
Ultrasonic Doppler Flow Velocity Meter
Measurement Principle
The ultrasonic Doppler flow velocity meter operates by placing an ultrasonic sensor in the channel or river to be measured. The sensor emits ultrasonic waves into the water, and the water flow velocity is calculated based on the intensity of the reflected ultrasonic signals and other parameters. This data is transmitted to the user through built-in hardware and software. It is widely used as a device for measuring water flow velocity in pipelines, channels, or rivers.
Main applicable environments include:
·Flood disaster monitoring
·Sewage discharge
·Natural rivers and streams
·Municipal water supply and drainage
·Water loss/seepage monitoring
·Irrigation process monitoring
·Estuary and tidal research
·Fisheries/water conservancy
·Coastal erosion research
·Culvert flow monitoring
·Road drainage monitoring
·Canal flow research
·River flow monitoring
A battery-powered system can be provided upon request to supply power in areas where power supply is inconvenient.
A GPRS wireless transmission kit can be provided upon request to view field-detected data on a backend server.
Product Features
1. Product and Technical Parameters
1.1 Flow velocity measurement principle: Uses the Doppler frequency shift physical principle to measure water flow velocity.
What is the Doppler effect (Doppler frequency shift):
The sound waves emitted by the ultrasonic sensor are received and reflected by another receiving body. If the sound source is moving relative to the receiving body, the frequency of the sound waves received by the receiving body will differ from the transmission frequency of the sound source.
If the relative distance between two objects is decreasing, the received frequency will increase.
If the relative distance between two objects is increasing, the received frequency will decrease.
This Doppler effect often occurs in daily life. For example, when you hear the whistle of an approaching train or the siren of a police car (a sound source), the sound appears to have a higher frequency; when the train or police car moves away from you, the sound you hear becomes lower.
The specific flow velocity is calculated based on the difference between the transmitted ultrasonic frequency and the received ultrasonic frequency.
Technical Parameters
Structure: Split type;
Measurement types: Flow velocity, water depth (water temperature measurement is an optional function)
Application: Online measurement
Acidity/alkalinity: pH value between 6 and 10
Liquid pressure requirement: Under natural environmental conditions, 1 standard atmospheric pressure
Notes: 1. Flow velocity cannot be measured when water is frozen or near freezing.
2. The default maximum water depth cannot exceed 10 meters. If it exceeds 10 meters, please inform the manufacturer before ordering.
1.4 Measurement Status and Wiring
Data is calculated 60 seconds after power-on, and then measurement data is calculated every 10-15 seconds. (The data here is not actively uploaded but passively uploaded; the host computer needs to send a query command to obtain the measured data.)
The cable is a four-core shielded cable, with two wires for power and two wires for 485 signal.
The power wire is red for positive, white for negative, blue for 485A, and yellow for 485B.
Product Structure Diagram
Product Actual Photos
On-site Voltage Stabilization Testing
The ultrasonic Doppler flow velocity meter sensor has a stainless steel mounting base. The four holes on the base are used for fixing to the ground, and the side opening is used for securing the sensor with a clamp.
Sensor Mounting Base Diagram
2. Product Installation
2.1 Selection of Installation Location
Choose a location with stable water flow for measurement.
In places with unstable water flow, turbulence is common in most cases. The flow velocity measured under turbulent conditions fluctuates, is unstable, and has large errors.
Figure 2.1.1 Select a channel section with stable flow velocity for installation
2.2 Requirements for Upstream and Downstream Channels
Under ideal conditions, there should be a straight channel 10 times the channel width upstream of the flow meter installation location, and a straight channel 3 times the width downstream.
Figure 2.2.1 Requirements for Upstream and Downstream Straight Channels
The longer the upstream straight channel, the better. The longer it is, the more stable the water flow, and the closer the flow velocity measurement is to the actual flow velocity. And this section must not have any obstructions, such as gates, weirs, etc., to ensure that the water flow at the front end of the sensor is stable and free of turbulence.
Figure 2.2.2 The Longer the Upstream Straight Channel, the Better
If 10 times the upstream straight channel cannot be achieved, there must be at least 5 times the channel width, not less than 5 times.
Example: For a rectangular channel with a width of 2 meters, how long should the upstream and downstream straight channels be at the sensor installation location?
Figure 2.2.3 Requirements for Upstream and Downstream Straight Channels for a 2-Meter Wide Channel
Example: For a trapezoidal channel with an upper bottom width of 5 meters, a lower bottom width of 2 meters, and a height of 2 meters, how should the channel width be calculated?
Figure 2.2.4 How to Determine the Width of a Trapezoidal Channel
The width at the highest water level during the flood season is taken as the channel width. If the flood season water level exceeds the highest point of the trapezoidal channel, the width of the upper bottom edge of the trapezoidal channel is used as the standard.
If the width of the highest water level during the flood season is 4 meters, there should be a straight channel of 20-40 meters upstream of the installation location and a straight channel of 12 meters downstream.
Figure 2.2.5 Calculation of Upstream and Downstream Straight Channel Lengths for a Trapezoidal Channel
2.3 Requirements for Installation Downstream of a Gate
If installed downstream of a gate, special attention should be paid to observing whether the water surface is stable.
Figure 2.3.1 Downstream of a Gate
If the distance between the sensor installation location and the gate is already 10 times the channel width, but the water surface is still unstable, the distance between the sensor and the gate needs to be increased until the water flow is stable.
Because within a certain distance downstream of the gate, there are usually reinforced concrete channels that are relatively regular. Many sites choose to install at a relatively close distance downstream of the gate for installation convenience. The water flow in such places is generally turbulent and chaotic, and the measured data differs greatly from the actual flow velocity.
This location is not suitable for installation.
Figure 2.3.2 Incorrect Installation Point - Installation at the Gate Outlet
2.4 Selection of Installation Height
First, determine the water level height during the dry season. The sensor should be 10 cm lower than the lowest water level.
The sensor should be installed as close to the channel bottom as possible. If there is a lot of sediment, silt, aquatic plants, or rolling stones at the channel bottom, the installation position can be raised to avoid the probe being covered by sediment and aquatic plants or being impacted by stones.
The ideal height of the probe from the channel bottom is 100mm-250mm, which should be determined according to the lowest water level of the channel.
Figure 2.4.1 The Sensor Should Be 10 cm Lower Than the Lowest Water Level
When the channel water level is relatively high and the lowest water level is also relatively high, for installation convenience, the probe can be installed at 0.5 times below the lowest water level.
Example: If the lowest water level is 1.00 meter, it can be installed at 0.50 meters from the channel bottom.
Figure 2.4.2 Sensor Installed at Half the Lowest Water Level
2.5 Selection of Horizontal Installation Position
For channels less than 20 meters wide, if it is a rectangular channel, install at 15-20% of the entire channel width.
Why install at this position?
Because installation at this position is closest to the average flow velocity in the horizontal direction of the entire channel.
Figure 2.5.1 Sensor Installed at 15-20% of the Entire Channel Width
For trapezoidal channels, the sensor is installed at the junction of the slope and the bottom edge, also known as the "slope toe".
Figure 2.5.2 Sensor Installed at the "Slope Toe" of a Trapezoidal Channel
The sensor must face the direction of water flow directly, with a left-right deviation not exceeding ±3°.
Figure 2.5.3 The Sensor Must Face the Direction of Incoming Water Flow
The sensor must be parallel to the water surface.
Figure 2.5.4 The Sensor Must Be Parallel to the Water Surface
2.6 Sensor Installation in Circular Channels
Figure 2.6.1 Circular Pipeline
In circular pipelines, if there is sediment, install the sensor above the sediment to avoid sediment covering the sensor and affecting measurement.
Figure 2.6.2 Installation Position in Pipelines with Sediment
For installation in pipelines without sediment, it can be installed directly at the channel bottom. To prevent water flow impact from changing the sensor installation position, there is a base at the bottom of the sensor specifically for fixing to the pipeline. At the same time, the sensor should be installed near the pipeline outlet, which is convenient for installation and beneficial for maintenance and replacement.
Figure 2.6.3 Installation Position in Pipelines Without Sediment
2.7 Sensor Installation in Rectangular Channels
For installation in rectangular channels, if water can be cut off to expose the channel bottom, a cement platform can be made at the channel bottom, with 4 bolts fixed on the cement platform. The mounting base of the flow velocity meter can be directly fixed to the bolts with nuts.
The advantage of this installation is that it is not easy to be stolen.
Disadvantage: Once maintenance is required, personnel must go down into the channel to operate.
Figure 2.7.1 Installation in a Rectangular Channel at a Reservoir Outlet
For installation in channels with silt accumulation, the installation position should be raised to reduce the impact of silt accumulation on measurement.
Figure 2.7.2 Installation in a Rectangular Farmland Irrigation Channel - With Silt and Aquatic Plants
For channels where water cannot be cut off, the following side bracket installation can be used. When the sensor is covered by silt or a large amount of garbage, simply unscrew the screws fixing the entire bracket to the shore-side fixing bracket to lift the sensor out of the water for cleaning.
Figure 2.7.3 Bracket Method Installation for Rectangular Channel Sensors
A small measurement bridge can also be erected over the rectangular channel, and the flow velocity meter can be fixed to the small bridge with a bracket for measurement.
Figure 2.7.4 Installation on a Measurement Bridge at Baiyun Reservoir, Yongtai County
2.8 Sensor Installation in Trapezoidal Channels
If water can be cut off, installation can be done as shown in Figure 2.7.1. If water cannot be cut off, a bracket is generally made on the shore, with 2 suspended rods extending downward from the bracket. The rods meet at the part where the sensor is installed, and then the sensor is fixed on the platform at the junction.
The 2 suspended rods are connected to the vertical rod through a rotating shaft, ensuring they can rotate up and down. When needed, the sensor can be pulled out of the water for maintenance and handling.
2.8.1 Schematic Diagram of Installation in a Trapezoidal Channel - Suspended Bracket
Figure 2.8.2 Fuzhou Inland River - Suspended Bracket Method Installation
Figure 2.8.3 Fuzhou Inland River - Suspended Bracket Method Installation
If the slope is relatively long, installation with the suspended bracket method may not be stable enough. The "tracked slide" method can be used for installation. A tracked slide is laid from the top of the trapezoidal channel to the bottom of the channel. The mobile platform is fixed to the tracked slide through slide rails and can move up and down. The sensor is fixed on the slide.
This method is particularly convenient for daily inspection and maintenance.
2.8.4 Schematic Diagram of Installation in a Trapezoidal Channel - Tracked Slide
3. Product Usage Precautions
1. The sensor is connected to other equipment through cables, which should be led out of the water along the channel bottom or inner wall from the downstream direction of the sensor.
2. Cables must be protected by sleeves (PVC, PR, galvanized pipes, etc.). Water flow must not directly impact the cables, and the sleeves must be fixed to the bracket or channel wall.
3. The communication cable that comes with the sensor contains a ventilation duct, so be careful not to bend it. When the communication cable is led out of the water, it can be connected to an ordinary cable. At this time, the opening direction of the ventilation duct should face downward to prevent water and foreign objects from entering or blocking the ventilation duct.
Cables connecting to the 485 or 12VDC power supply on the sensor must use shielded cables of 0.5 square millimeters or more.
4. When using a wireless transmitter in irrigation channels, the antenna must be led out of the instrument box, and lightning protection measures must be taken to prevent the antenna from becoming a target for lightning strikes.
5. Do not artificially pull or swing the cables, and do not impact the sensor housing.
6. Do not use the connecting cable as a load-bearing line to hang heavy objects. The cable must be fixed to the cement wall of the channel and must not shake.
7. Power supply can only be battery power or solar power. If using 220VAC mains power, a linear power supply must be used to convert it to 12VDC direct current; switching power supplies cannot be used.
8. For sites with flow velocity > 1.0 m/s, the strength of the mounting bracket should be strengthened to more than 2 times that of the existing bracket to ensure that rapids will not wash away or damage the bracket.
Fuzhou Dayu Electronics——Not only a manufacturer of ultrasonic Doppler flow velocity meters, we are also experts in producing ultrasonic Doppler flow meters and river flow meters. We have always adhered to the tenet of providing customers with good products and good service solutions. If you are interested in the above products or have any questions, please contact our online customer service QQ:2187169532, service hotline:0591-28082552. Fuzhou Dayu Electronics——Your considerate procurement consultant throughout the process!