What are the common types of flow velocity measuring instruments?

Release time：

2025-11-14

　　Flow velocity measurement is a core technical link in fields such as water resources management, environmental monitoring, and industrial production. With the development of the Internet of Things (IoT) and intelligent sensing technology, flow velocity measuring instruments have formed a diversified technical system, ranging from traditional mechanical types to non-contact radar and acoustic Doppler technologies. As an industry technology integrator, Xiamen Haichuan Runze IoT Technology Co., Ltd. covers mainstream flow velocity measurement technologies in its product line, providing precise solutions for different scenarios.

　　I. Mechanical Rotational Current Meters: Modern Optimization of Traditional Technology

　　Mechanical rotational current meters measure velocity by the rotation of sensing elements driven by water flow, and they are the most widely used basic equipment in hydrological monitoring. Their core component is a sensing element with blades or a rotor. When fluid flows through, the rotational speed of the blades is proportional to the flow velocity. The number of rotations is transmitted to a counter through a mechanical transmission device, and the flow velocity is obtained through conversion.

　　Technological Evolution

　　Traditional propeller-type current meters (such as LS68 and LS78 models) adopt metal propellers and mechanical counters, suitable for medium and low flow velocity scenarios. The HC-CS9091 Acoustic Doppler Flow Velocity Meter launched by Xiamen Haichuan Runze integrates an acoustic Doppler sensor on the basis of retaining the mechanical structure. It corrects mechanical measurement errors through changes in ultrasonic reflection frequency, expanding the velocity measurement range to 0.02-6.00 m/s with an accuracy improved to ±1.0%. It also supports synchronous water level measurement, suitable for complex environments such as open channels and irrigation canals.

　　Industry Adaptation

　　This technology is widely used in scenarios such as river discharge monitoring and farmland irrigation canal flow measurement. Its advantages lie in simple structure and low cost, but it requires contact measurement and has weak adaptability to turbulent water flow or water containing impurities.

　　II. Ultrasonic Current Meters: Technological Breakthrough in Non-Contact Measurement

　　Ultrasonic current meters measure velocity using the propagation characteristics of sound waves in fluids, divided into two major technical paths: Doppler effect and time-difference method, breaking the limitations of traditional mechanical contact measurement.

　　1. Doppler Ultrasonic Current Meters

　　Principle: Emit ultrasonic waves of fixed frequency to the fluid. When the sound waves encounter suspended particles or bubbles, they scatter, and the frequency of the reflected waves shifts due to the Doppler effect. The flow velocity is calculated by detecting the frequency change. The HC-CSLD100-01 Ultrasonic Radar Flow Meter of Xiamen Haichuan Runze adopts dual-frequency ultrasonic technology, which can simultaneously measure flow velocity and particle concentration. The minimum applicable water level is only 15 cm, suitable for impurity-containing fluids such as urban drainage pipelines and industrial sewage.

　　Technical Advantages: Non-contact measurement avoids interference with water flow and has strong tolerance to suspended solids and bubbles. However, in clear water, insufficient scatterers may lead to decreased accuracy, which needs to be optimized through algorithm compensation.

　　2. Time-Difference Ultrasonic Current Meters

　　Principle: Install ultrasonic transmitters and receivers symmetrically on both sides of the fluid. Measure the time difference of sound waves propagating downstream and upstream, and calculate the flow velocity combined with fluid cross-sectional parameters. The HCRZ-LL100 Radar Flow Meter of Xiamen Haichuan Runze integrates ultrasonic time-difference method with radar wave surface velocity measurement technology, realizing high-precision measurement of large-diameter pipelines (diameter ≥ 200 mm) and open channels. The velocity measurement range reaches -20 to 20 m/s, suitable for scenarios such as water conservancy project channels and urban water supply pipelines.

　　Technical Advantages: Measurement accuracy is not affected by water quality, and long-distance transmission can be achieved. However, installation requires precise calibration of the angles of transmitters and receivers, and the equipment cost is relatively high.

　　III. Radar Current Meters: Reliable Choice for Extreme Environments

　　Based on the Doppler effect, radar current meters calculate flow velocity by emitting electromagnetic waves and detecting changes in the frequency of reflected waves. Their non-contact measurement characteristics make them the preferred tool in high floods and harsh environments.

　　Technical Principle

　　Emit high-frequency electromagnetic waves (usually 24 GHz or 35 GHz) to the fluid surface. When the electromagnetic waves encounter the flowing water surface, they reflect, and the frequency of the reflected waves produces Doppler shift due to fluid movement. The surface flow velocity is calculated through the linear relationship between the shift amount and the flow velocity. The HC-LS100 High-Frequency Radar Sensor of Xiamen Haichuan Runze adopts pulse coherent Doppler technology, which can work stably under conditions such as strong wind, heavy rain, and floating object interference. The velocity measurement range is 0.01-15 m/s, suitable for open waters such as rivers, lakes, and oceans.

　　Technological Breakthrough

　　Traditional radar current meters are susceptible to water surface fluctuations, leading to measurement errors. The HC-LS100 can distinguish real flow velocity signals from wave interference through an adaptive filtering algorithm, and integrates a temperature compensation module to eliminate the influence of ambient temperature on the propagation speed of electromagnetic waves, ensuring data accuracy.

　　IV. Acoustic Doppler Current Profilers (ADCP): Accurate Capture of Three-Dimensional Flow Fields

　　ADCP is a core equipment in oceanography and river dynamics research. It realizes the measurement of the three-dimensional spatial distribution of flow velocity through an acoustic array, providing basic data for the construction of water flow movement models.

　　Technical Principle

　　Emit multiple beams of sound waves to the fluid. After the sound waves encounter scatterers (such as sediment and bubbles), they return. The flow velocity and direction at different depth layers are calculated by analyzing the reflection frequency shifts of each beam of sound waves. The H-ADCP Acoustic Doppler Profiler Flow Meter of Xiamen Haichuan Runze adopts a four-beam transducer array, which can simultaneously measure water depth, flow velocity, discharge, and flow direction. The depth measurement range reaches 50 meters, suitable for discharge monitoring in rivers, canals, and offshore areas.

　　Technical Advantages

　　Compared with single-point measurement instruments, ADCP can obtain vertical profile data of flow velocity, revealing the water flow stratification structure and turbulence characteristics. However, its equipment cost is high, and professional software is required for data processing.

　　V. Intelligent Integrated Measurement Systems: Innovative Applications in the IoT Era

　　With the development of IoT technology, flow velocity measuring instruments are evolving from single devices to intelligent and networked systems. The ecological flow monitoring system launched by Xiamen Haichuan Runze integrates radar current meters, ultrasonic water level gauges, remote terminal units (RTU), and data analysis platforms, realizing real-time monitoring and remote transmission of parameters such as flow velocity, water level, and discharge.

　　System Architecture

　　After front-end sensors collect data, they transmit it to the cloud platform through wireless modules (such as 4G/LoRa). The platform automatically calculates discharge based on the velocity-area method and generates visual reports such as flow curves and alarm thresholds. The system supports collaborative work of multiple devices and can simultaneously monitor flow velocities at multiple sections, suitable for large-scale water area management such as reservoirs, hydropower stations, and irrigation areas.

　　Technical Value

　　Intelligent integrated systems break the data silo problem of traditional measurement equipment and optimize water resources scheduling strategies through big data analysis. For example, in agricultural irrigation, the system can dynamically adjust irrigation volume according to real-time flow velocity and soil moisture data, achieving water conservation and efficiency improvement.

　　VI. Key Considerations for Technology Selection

　　The technical characteristics of different flow velocity measuring instruments determine their applicable scenarios. The following factors need to be comprehensively evaluated when selecting:

　　Measurement Environment: For impurity-containing water, Doppler ultrasonic or ADCP is preferred; for open waters, radar current meters are recommended; for clear water, time-difference ultrasonic or laser current meters should be used.

　　Accuracy Requirements: For scientific research-level measurement, ADCP or laser current meters are needed; for engineering monitoring, mechanical rotational or intelligent integrated systems can be used.

　　Cost Constraints: Mechanical rotational type has the lowest cost; intelligent integrated systems have high initial investment but low long-term operation and maintenance costs.

　　Installation Conditions: Non-contact instruments (radar, ultrasonic) are easy to install; ADCP requires a fixed installation platform, suitable for long-term monitoring stations.

　　The technological evolution of flow velocity measuring instruments has always centered on the three core needs of "accuracy, reliability, and intelligence". From traditional mechanical types to modern acoustic and radar technologies, and then to IoT integrated systems, each technological breakthrough has expanded the application boundaries of flow velocity measurement. By integrating diversified technologies, Xiamen Haichuan Runze IoT Technology Co., Ltd. provides complete solutions from single-point measurement to systematic monitoring for water conservancy, environmental, industrial and other fields, promoting the development of flow velocity measurement technology towards higher accuracy and stronger adaptability.