ADCP Acoustic Doppler Current Profiler

ADCP Acoustic Doppler Current Profiler

Full name: Acoustic Doppler Current Profilers (ADCP) refers to a flow measurement device developed in the early 1980s. ADCP can directly measure the velocity profile of a cross-section, does not disturb the flow field, requires short measurement time, and has a wide velocity measurement range. It is currently used for flow field structure surveys, velocity and discharge measurements in oceans and estuaries.

I. Product Photos and Introduction

The product measures flow velocity based on the ultrasonic Doppler effect. It emits an ultrasonic pulse into the water and receives reflected echo signals from particles and bubbles in the water. The velocity change is calculated from the frequency shift of the echo signal, and the stratification of velocity is determined by the time sequence of the echo signals. Water level is measured via a pressure sensor, and water temperature via a temperature sensor.

This single-beam Acoustic Doppler Current Profiler is typically mounted on the bottom. By emitting ultrasonic pulses, it can remotely measure the velocity of each water layer. It also outputs the date and time of measurement (year, month, day, hour, minute, second), roll angle, pitch angle, and temperature, facilitating correction to obtain accurate flow velocity.

The housing is made of POM plastic (polyacetal, a crystalline thermoplastic), with a distinct melting point of 165–175°C, and properties closest to metal, commonly referred to as plastic steel. It is designed for deep-sea pressure resistance and provides effective waterproof sealing.

* Uses Modbus communication protocol over RS485 bus.

* Host computer for data acquisition. Supports one-to-many operation (one host connected to multiple slave devices).

* Simple communication commands.

* Easy installation of underwater sensor. Equipped with a metal base fixing bracket for simple installation.

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

* Wide range of applications, from tap water to Yellow River water environments.

 II. Product Principle

Single-beam Acoustic Doppler Current Profiler principle: When the ultrasonic source and the observer move relative to each other, the frequency received by the observer differs from the source frequency. Therefore, small particles and bubbles moving with the water relative to the ultrasonic transducer also cause a change in the received frequency, which increases with the velocity of suspended motion. By measuring the Doppler shift, the water flow velocity is determined.

Mainly used in irrigation open channels, municipal sewage pipes, and hydrologic basins, especially suitable for water depths from 0.5 meters to several meters. In regular pipes and channels, water depth is measured by the pressure sensor on the current meter, layer velocities by the ultrasonic sensor, and flow rate can be conveniently calculated using background calculation software.

III. Product Technical Specifications

Table 1 Measurement Specifications

Table 2 Performance Specifications

IV. Installation Requirements

The Acoustic Doppler Current Profiler should be installed in the downstream straight section of a channel with a fixed cross-section. The longer the straight section, the higher the measurement accuracy. There should be no flow-obstructing objects (such as sluice gates or weirs) within 10 meters to ensure uniform and stable flow at the probe front. Install away from the riverbanks, horizontally at the center between the two banks, and vertically at the bottom (provided the channel has no silt; if silt is present, place it above the silt). As shown in Figure 1, when there is sediment deposit, aquatic weeds, or rolling pebbles at the channel bottom, the installation position can be raised to avoid the probe being covered by sediment or weeds or hit by pebbles. The recommended height of the current meter above the channel bottom is 5 cm, depending on the minimum flow level of the channel. When the water depth is high and there is a certain minimum water level, for installation convenience, the probe can be installed at 0.5 times the depth below the minimum water level.

Figure 3 Doppler Current Profiler Installation

The host computer is generally installed on a pole on the bank or inside an equipment room, as shown in Figure 2. The host computer controls the measurement interval of the Doppler current profiler. To save power, the profiler is often powered on only during data collection, and a measurement command is issued, then powered off between measurements. Flow rate can be calculated from the measured water level and velocity data, or the raw velocity and water level information can be time-stamped and stored, or transmitted remotely via SMS, GPRS, etc.

During installation, the air-vent cable should be routed along the channel bottom and wall, leading out of the water downstream from the current meter. It is recommended to protect it with PVC pipe or stainless steel conduit and secure it along the way. When using an arm-type bracket to fix the probe, the air-vent cable can be routed through the hollow steel tube of the bracket to the water surface.

The Doppler current profiler comes with a 20-meter air-vent cable, which contains an air tube used to balance atmospheric pressure. The air tube has an outer diameter of about 2 mm and an inner diameter of about 1 mm. Therefore, do not bend it excessively. After the communication cable is led out of the water, it can be connected to a regular cable. In this case, the opening of the air tube should face downward and be protected with breathable tape to prevent water and foreign matter from entering.

The four-core wires in the air-vent cable are generally green (+12V), white (GND), blue (RS485A), and yellow (RS485B). (Any changes will be notified upon delivery.)

The 12V power supply for the Doppler current profiler can come from a battery, solar power, or mains electricity. Currently, there are two main types of converters from AC 220V to 12V: linear power supplies (using a power transformer) and switching power supplies (the most popular). When selecting a power supply, linear types are preferred because many switching power supplies on the market have poor quality and high ripple, failing to meet EMC standards, which can interfere with ultrasonic measurement.

Figure 4 Measurement System Installation Diagram

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

Figure 5 Base Plate Hole Positions

V. Precautions

1. Since the air-vent cable contains an air tube, do not bend it excessively to prevent breakage. Never use the air-vent cable as a tow rope to drag the Doppler current profiler.

2. The air tube inside the air-vent cable connects to the circuit board inside the probe and must not allow water ingress. When installing, the opening of the air tube should face downward to prevent moisture from condensing and flowing along the tube wall into the probe circuitry.

3. When routing the air-vent cable out of the water from the probe, it should be protected with PVC pipe or routed inside a bracket tube, secured along the way, to avoid direct hydraulic impact and tension, especially in channels with abundant aquatic weeds.

When weeds get caught on the cable, significant tension can occur and may break the air-vent cable.

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

5. Connections between the host computer (integrator) and the probe must be correct; otherwise, the instrument may be damaged.

6. Avoid prolonged exposure of the probe to direct sunlight to prevent overheating (probe temperature must not exceed 70°C).

7. In areas with high sediment concentration, the ultrasonic transducer and pressure sensor should be cleaned regularly to prevent mud from clogging the pressure sensor.

Fuzhou Dayu Electronics — Manufacturer of ADCP Acoustic Doppler Current Profilers, your considerate product consultant.

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