ADCP Acoustic Doppler Current Profiler

ADCP Acoustic Doppler Current Profiler

The full name is Acoustic Doppler Current Profiler, a flow measurement device developed in the early 1980s. ADCP features the ability to directly measure velocity profiles of cross-sections without disturbing the flow field, short test duration, and wide velocity measurement range. It is currently used for flow field structure surveys in oceans and estuaries, as well as velocity and discharge measurements.

I. Product Photos and Introduction

The product measures flow velocity based on the ultrasonic Doppler effect principle. By emitting an ultrasonic pulse into the water and receiving echo signals reflected from particles and bubbles in the water, it calculates velocity changes based on the frequency variation of the echo signals, and then determines the velocity stratification based on the time sequence of the echo signals. It can also measure water level through a pressure sensor and water temperature through a temperature sensor.

This single-beam acoustic Doppler current profiler is typically bottom-mounted, allowing remote measurement of flow velocity at various water layers through the emission of ultrasonic pulses. It can simultaneously output the year, month, day, hour, minute, second, roll angle, pitch angle, and temperature values during testing, facilitating correction to obtain accurate flow velocity.

The housing is made of POM plastic (scientific name: polyacetal, a crystalline thermoplastic) with a distinct melting point of 165-175°C. Its properties are closest to metal, and it is commonly called "plastic steel." It features a deep-sea pressure-resistant design that effectively provides waterproof sealing.

* Adopts Modbus communication protocol, utilizing RS485 bus for communication.

* Data acquisition host computer. Capable of one-to-many usage (one host computer mounting multiple slave devices).

* Simple product communication commands.

* Easy installation of underwater sensor equipment. Features metal base fixing device for simple installation.

* The equipment adopts fully electronic design with no mechanical parts. Features accurate and stable measurement, high reliability, and strong anti-interference capability.

* Wide application range. Can be applied in various water environments from tap water to Yellow River water.

 II. Product Principle

Single-beam acoustic Doppler current profiler principle: When the ultrasonic sound source and observer are in relative motion, the frequency received by the observer differs from the ultrasonic sound source frequency. Therefore, small particles and bubbles moving with water relative to the ultrasonic transducer also cause changes in the transducer's received frequency, which increases with the speed of suspended movement in water. This measures the Doppler frequency shift, thereby measuring the water flow velocity.

Mainly used in irrigation open channels, municipal sewer pipes, hydrological watersheds, and other occasions, particularly suitable for water areas with depths exceeding 0.5 meters to several meters. In regular pipes and channels, the pressure sensor on the flow velocity meter measures water depth, the ultrasonic sensor measures flow velocity at various layers, and the background calculation software can conveniently calculate the flow rate.

III. Product Technical Specifications

Table 1 Measurement Specifications

Table 2 Performance Specifications

IV. Installation Requirements

The acoustic Doppler current profiler should be installed downstream of a straight channel section with a fixed cross-section. The longer the straight section, the higher the measurement accuracy. There must be no flow obstructions (such as gates, weirs, etc.) within a 10-meter distance to ensure uniform and stable water flow conditions at the front of the probe. The installation position should avoid areas near river banks as much as possible, placed horizontally at the center between both banks and vertically at the bottom of the water (provided the waterway has no silt; if present, the placement position should be higher than the silt). As shown in Figure 1, when there is impurity deposition, aquatic plant growth, or rolling pebbles at the channel bottom, the installation position can be raised to avoid channel bottom sediments and aquatic plants covering the probe or pebbles hitting the probe. The specific height of the acoustic Doppler flow velocity meter from the channel bottom is preferably 5 cm, depending on the minimum measurable water level of the channel. When the channel water depth is high and there is a certain minimum water level, for installation convenience, simply install the probe 0.5 times below the minimum water level.

Figure 3 Doppler Current Profiler Installation

The host computer is generally installed on a utility pole on shore or in a machine room, as shown in Figure 2. The function of the host computer is to control the measurement interval of the Doppler current profiler through settings. Generally, to save power, the Doppler flow velocity meter is powered on during data collection and measurement commands are issued, and the Doppler flow velocity meter is powered off between two measurement intervals. The flow rate can be calculated from the measured water level and flow velocity data, or the original flow velocity and water level information can be directly time-stamped and stored, or data can be transmitted remotely using SMS, GPRS, and other means.

During installation, the air-conducting cable should be led out of the water along the channel bottom and channel wall from the downstream direction of the flow velocity meter. It is best to cover it with PVC pipe or stainless steel pipe for protection and fix it along the route. When using an arm bracket to fix the probe, the air-conducting cable can be led out of the water along the hollow steel pipe of the bracket.

The Doppler current profiler comes with a 20-meter air-conducting cable, which has an air-conducting tube in the middle to balance atmospheric pressure. The outer diameter of the air-conducting tube is about 2mm and the inner diameter is about 1mm. Therefore, be careful not to bend it. After the communication cable is led out of the water, ordinary cables can be connected. At this time, the opening direction of the air-conducting tube should face downward and be protected with breathable tape to prevent water and foreign matter from entering the air-conducting tube.

The four-core wires in the air-conducting cable are generally green (connect to +12V), white (connect to GND), blue (connect to RS485A), and yellow (connect to RS485B). (Users will be notified of any changes at the time of delivery)

The 12V power supply used by the Doppler current profiler can come from batteries or solar power, and of course from mains electricity. Currently, there are two main types of power supplies that convert AC 220V to 12V: one is a linear power supply, which uses a power transformer; the other is a switching power supply, which is currently the most popular. When selecting a power supply, try to use a linear power supply. Because switching power supply brands on the market are mixed, some switching power supplies have large ripple and do not meet relevant electromagnetic compatibility standards, which can easily interfere with ultrasonic measurement.

Figure 4 Measurement System Installation Diagram

The Doppler current profiler comes with a 2.5mm thick stainless steel plate as the mounting base plate. The specific installation hole dimensions are shown in Figure 5.

Figure 5 Base Plate Hole Positions

V. Precautions

1. The air-conducting cable contains an air-conducting tube inside, so it cannot be bent excessively to prevent breakage. Never use the air-conducting cable as a rope for the flow velocity meter or use it to drag the Doppler flow velocity meter.

2. The air-conducting tube inside the air-conducting cable is connected to the circuit board inside the probe and cannot get water in. During installation, the end opening of the air-conducting tube should face downward to prevent moisture from condensing and flowing into the probe circuit along the tube wall. 

3. When the air-conducting cable is led out of the water from the probe, it should be covered with PVC pipe for protection and fixed along the route, or routed through the pipe of the bracket to avoid direct hydraulic impact that generates tension, especially in channels with abundant aquatic plants where grass hanging on the cable can generate significant tension and potentially break the air-conducting cable.

4. The circular ultrasonic transducer in front of the probe must not be subjected to impact or scratches. 

5. The wiring between the host computer (integrator) and the probe must be correctly connected, otherwise it will cause instrument damage.

6. The instrument probe should avoid prolonged exposure to sunlight to prevent malfunctions caused by excessive temperature (the probe temperature must not exceed 70°C).

7. When using the acoustic Doppler current profiler in areas with high sediment concentration, regularly clean the silt on the ultrasonic transducer and pressure sensor to prevent silt from clogging the pressure sensor.

Fuzhou Dayu Electronics - ADCP Acoustic Doppler Current Profiler Manufacturer, your caring product consultant.

For more detailed information, please call the hotline: 0591-28082552  or add corporate QQ: 2187169532  Fuzhou Dayu Electronic Technology Co., Ltd. will serve you wholeheartedly!