Ultrasonic Open Channel Flow meter

Ultrasonic open channel flow meter can measure the water level, flow rate, and total volume flowing through weirs, troughs, channels, and partially filled pipes. Ultrasonic open channel flow meter is used in conjunction with Parshall flume. Using hydraulic flow measurement, ultrasonic positioning, microcomputer processing, digital display, and other technologies. It can be installed and automatically measured in harsh environments. Commonly used for agricultural irrigation water discharge measurement, wastewater, sewage, and other measurements.

Sino-Inst offers a variety of  Ultrasonic flow meters for flow measurement. If you have any questions, please contact our sales engineers.

Features of Ultrasonic Open Channel Flow Meter

  • Ultrasonic non-contact liquid level measurement does not affect the flow rate at all. Accurate liquid level measurement is an ideal level meter.
  • The probe has low power consumption, simple installation and easy positioning. It is widely used in rivers, water supply, factories, urban sewage pipelines and other related fields.
  • The flow totalizer is easy to operate and suitable for wide types of water measuring weirs, including thin-walled right-angled triangular weirs, rectangular weirs, and Parshall grooves.
  • The flow totalizer has the function of historical flow recording. It can record the flow data of the past 60 hours, 30 days, 12 months, and 10 years. More historical data can be recorded in real time through the SD card.
  • Comprehensive instrument control functions, four-way relay signal output, easy to connect to commonly used actuators (motors, alarms, etc.).
  • According to the requirements of working conditions, the probe can choose special models such as IP68, anti-corrosion, explosion-proof, small blind area high-precision, ultra-low power consumption, large range and other special models.
  • Built-in remote communication module, various communication protocols can be customized (customized when ordering).

Extended reading: Flow Totalizer Meter vs Flow Meter

Specifications of Ultrasonic Open Channel Flow Meter

StructureOne-piece and split type
Measuring range0.1m³/h~99999.99m³/h is determined according to different weirs and troughs
Cumulative flowThe maximum is: 429000000.00m3
Level measurement accuracy0.50%
Resolution3mm or 0.1% (whichever is greater)
Flow measurement accuracyStandard weirs and troughs 1~5% (weir troughs and channels that meet the requirements of the national standard),
non-standard weirs and troughs 10~50%
powered by220VAC±15% 50HZ, or 24VDC 120mA, (optional) 12VDC,
battery powered, solar powered
Protection levelDisplay instrument IP66, probe IP68
Probe selection instructionsIt is recommended to use 100KHz M48×2 probe for No.1-5 Parshall grooves,
The measuring range is 1 meter, it is not easy to hit the wall or corner of the Parshall groove to form false signals;
The probe blind area is small, only 10-13 cm, and the mounting bracket can be made lower;
It is recommended to use 64Khz M48×2 probe for No. 6-25 Parshall slot, measuring range 2 meters, blind area 30 cm.

Application of Ultrasonic Open Channel Flow Meter

Ultrasonic open channel flowmeter has a special structure with a Parshall groove. It can be used to continuously monitor the flow of sewage in the open channel and accumulate the flow. It is suitable for flow measurement under the conditions of water canal, agricultural irrigation, wastewater discharge, water conservancy, hydropower, environmental protection, and other industrial and agricultural open channels.

The open channel flowmeter transmits and receives ultrasonic waves under the control of a computer. Calculate the distance between the open channel flowmeter and the measured liquid surface according to the transmission time. So as to get the height of the liquid level.

So what problems should be paid attention to in the use of ultrasonic open channel flowmeters?

  1. The host of the ultrasonic open channel flowmeter should be installed indoors. Check lines and sensors regularly;
  2. Regularly check whether the filter screen and the still water well are blocked by foreign matter;
  3. Perform metrological verification of the instrument regularly;
  4. Regularly check the corrosion of the probe and replace it as needed

Ultrasonic open channel flowmeter has a special structure with a Parshall groove. It can be used to continuously monitor the flow of sewage in the open channel and accumulate the flow. It is used to measure the liquid flow in self-flowing partial pipes and open discharge channels. It is suitable for flow measurement under the conditions of water canal, agricultural irrigation, wastewater discharge, water conservancy, hydropower, environmental protection and other industrial and agricultural open channels.

Extended reading: Ultrasonic flow detectors types

Parshall Flume (PVC material, stainless steel material) for Open Channel Flow Meter

When choosing the type of weir and trough for measuring water, it is necessary to consider the size of the flow in the channel, the flow pattern of the water in the channel, and whether it can form a free flow. According to the different large flow, we can choose different weir grooves.

  • The large flow rate is less than 40 liters/sec. It is recommended to use a right-angled triangular weir;
  • It is recommended to use Parshall tank for more than 40 liters/sec;
  • The upstream channel is short, and the large flow rate is greater than 40 liters/sec. It is recommended to use a rectangular weir.

Conditions permit, a good choice of Parshall slot. The water level-flow relationship of the Parshall trough is calibrated by the laboratory, and the requirements for the upstream flow into the trough are relatively weak. The water level-flow relationship of the triangular weir and the rectangular weir is derived from theoretical calculations, and it is easy to cause additional errors due to ignoring some use conditions.

Use glass fiber reinforced plastic to make the measuring weir or trough. The size of the mouth of the triangular weir and the rectangular weir should be accurate, and the surface facing the water inlet should be smooth; the size of the throat part of the Parshall groove should be accurate, and the inner surface of the groove should be smooth.

Common installation methods and installation precautions of Parshall groove:

  • Put the Parshall trough into the open channel. Keep the trough level. The centerline of the Parshall trough should coincide with the centerline of the channel, so that the water flow into the Parshall trough does not appear drift.
  • After the Parshall trough is filled with water, the flow state of the water should flow freely. The submergence degree of the Parshall trough is less than the specified critical submergence degree.

Keep the downstream discharge of the Parshall trough unblocked. Do not accumulate water, if not unblocked. Keep the water level difference greater than or equal to 30MM.

The straight section before the Parshall trough has a distance buffer of 1 to 3 meters. The buffer channel should be level with the bottom of the trough. It is convenient for ultrasonic measurement.

It must be ensured that there is a water level difference downstream of the Parshall trough. The discharge is unobstructed and no water will accumulate.

Extended reading: Dam water level measurement

Open Channel Ultrasonic Flow Meter Working Principle

The open channel flowmeter is based on the specific shape of the Parshall metering groove/weir plate metering groove. It guarantees a certain liquid level and knows a certain flow rate. The Parshall groove/weir plate metering groove is selected as the specific flow channel. The measurement accuracy is high. Easy to install.

The sensor measures the height of the liquid level, which is processed by 89C52 series single-chip microcomputers to obtain the instantaneous flow and cumulative flow values.

The flow can be expressed by the following formula:
  Q: Instantaneous flow rate (t/h) K: Flow rate constant
  H: height of liquid level n: nth power value

The instantaneous flow is processed by the cumulative accumulation to obtain the cumulative flow.

Extended reading: Radar Non Contact Water Level Sensor

Inline Ultrasonic Flow Meter

Transit Time Ultrasonic Flow Meter adopts the measurement principle of the time difference method. It uses the ultrasonic wave emitted by the sensor to propagate in the flowing fluid. The sound wave propagation speed in the downstream direction will increase, and the backward direction will decrease. In the same propagation distance, there will be different transmission times. According to the difference between the transmission time and the measured The relationship between fluid velocity measures the fluid velocity.

The flow rate of the fluid is different in different positions in the tube. The flow rate in the center of the tube is faster than the flow rate near the wall of the tube. The flow velocity distribution of the fluid in the pipeline can be represented by the flow velocity cross-sectional distribution diagram.

By setting the flowmeter and considering the cross-sectional distribution of the flow velocity, the average flow velocity can be calculated. Then the volume flow of the fluid can be obtained according to the cross-sectional area of the pipe.

Clamp on Ultrasonic Flow Meter Working Principle

V measure fluid velocity
M ultrasonic reflection times
D pipe diameter
θ The angle between the ultrasonic signal and the fluid
T up The time when the downstream sensor transmits the signal to the upstream
T down Time from the upstream sensor to downstream
ΔT = T up – T down

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Ultrasonic Doppler Flow Meter uses the physical principle of Doppler frequency shift to measure the water flow velocity.

Doppler effect (Doppler frequency shift) principle:
The sound waves emitted by one object are received and reflected by another object. If the object emitting the sound wave is moving relative to the receiving object. The frequency of the sound wave received by the receiving object will be different from the frequency of the emitted sound wave.

If the relative distance between two objects is reduced, the received frequency will increase.
If the relative distance between two objects is increased, the received frequency will decrease.

Such Doppler effects often occur in daily life. For example: when you hear the sirens (sounds) of an oncoming police car. The sound will appear higher in frequency. When the police car is far away from you, the sound it hears will become lower.

Through the difference between the frequency of transmitting ultrasonic waves and the frequency of receiving ultrasonic waves, the specific flow rate can be calculated. Then the water level is measured by the pressure sensor, and the water passing area is calculated from the water level and channel size.
Finally, the velocity and area are integrated to calculate the final instantaneous flow.

Calculation formula:
Velocity × water area × 3600 seconds = instantaneous flow rate (cubic meters/hour)

Read mroe about: Irrigation Flow Meters for Agriculture Water System

Ultrasonic Open Channel Flow Meter Measures Sewage

Because the ultrasonic open channel flow meter uses open channel non-contact measurement. Therefore, the probe can be separated from the host. It can effectively solve the problems of probe corrosion and instrument accuracy, so it is widely used in irrigation and drainage and sewage measurement.

Ultrasonic Open Channel Flowmeter measures sewage.jpg

Read more about: Common River Water Level Measurement Methods

Note when installing:

  • To ensure that the sewage flowing through the flow tank has no foreign matter. A filter must be installed not far upstream of the flow tank;
  • To ensure that the sewage flowing through the flow tank is stable and without ripples. A still water well connected to the flow trough can be arranged on the side of the flow trough. The inner diameter of the well is ≥100mm. The bottom of the well should be 150mm below the lowest point of the trough. The width of the straight section of the trough ≥ 10 times the width of the water surface of the weir. The highest water level downstream is lower than the lowest water level of the weir;
  • The emission surface of the sensor probe should be parallel to the liquid surface. The distance between the lower end of the sensor and the highest liquid level should be ≥0.7 m;
  • There should be no strong light, electromagnetic field and other radiation sources around the sensor;
  • There should be measures to prevent rain and snow above the ultrasonic sensor.

Note in use:

  • Because the places where sewage ultrasonic sensors are installed are places with relatively poor environment. Therefore, the host of the instrument should be installed indoors. There should be a dedicated person to take care of it. Conduct regular inspections of lines and sensors;
  • The meter should be checked regularly.

Read more about: Waste water measurement

More Featured Ultrasonic Flow Meter


Open Channel flow meters measure level, flow rate and total volume of water flowing through weirs, flumes, channels and partially filled pipes. These meters perform best where the sediment does not build up.

Types of open channel flow meters (open channel flow measurement method)

In principle, open channel flow measurement methods can be divided into two categories: water level method and velocity area method.

The water level method is to measure the upstream (or upstream and downstream) water levels of water measuring buildings and convert them into flow through empirical formulas or experimental curves.

The velocity area method does not need to build a water measuring building, and the flow rate is obtained by measuring the cross-sectional area of the water (in fact, the cross-sectional area is calculated by the measured water level) and the cross-sectional velocity.

Ultrasonic flowmeter is composed of three parts: ultrasonic transducer, electronic circuit and flow display and accumulation system.

The ultrasonic transmitting transducer converts electrical energy into ultrasonic energy and transmits it into the measured fluid. The ultrasonic signal received by the receiver is amplified by the electronic circuit and converted into an electrical signal representing the flow rate for display and totalizer for display And accumulate. In this way, the flow detection and display are realized.

According to the detection method, it can be divided into different types of ultrasonic flowmeters such as propagation velocity difference method, Doppler method, beam shift method, noise method, and related method. The ultrasonic flowmeter is a kind that has only begun to be applied with the rapid development of integrated circuit technology in the past ten years.

The usual accuracy of our ultrasonic flowmeter is 1%. The highest is 0.5% for a liquid ultrasonic flowmeter and 1.0% for a gas ultrasonic flowmeter.

  1. According to the measurement principle

(1) Time difference method ultrasonic flowmeter;
(2) Frequency difference method ultrasonic flowmeter;
(3) Phase difference method ultrasonic flowmeter;
(4) Doppler ultrasonic flowmeter;
(5) Ultrasonic flowmeters for partially full pipes and river channels that combine liquid level measurement and average flow velocity measurement.

  1. According to the way of use

(1) Portable ultrasonic flowmeter;
(2) Fixed (standard pipe section) ultrasonic flowmeter.

  1. According to the installation method of the transducer

(1) Standard pipe section ultrasonic flowmeter;
(2) Clip-on ultrasonic flowmeter;
(3) On-site plug-in ultrasonic flowmeter with hole opening.

  1. According to whether the transducer is in contact with the fluid

(1) Immersion (contact) ultrasonic flowmeter;
(2) Non-invasive (non-contact) ultrasonic flowmeter.

  1. According to the nature of the measured fluid

(1) Liquid ultrasonic flowmeter;
(2) Gas ultrasonic flowmeter.

  1. According to the number of transducer channels

(1) Mono ultrasonic flowmeter;
(2) Two-channel ultrasonic flowmeter;
(3) Multi-channel ultrasonic flowmeter.

Sino-Inst, Manufacturer for Open Channel Flow Meters. It can measure a single sound-conducting liquid medium. It can measure even liquids such as water, seawater, oil, and slurry.

Sino-Inst’s Open Channel Flow Meter, made in China, Having good Quality, With better price. Our flow measurement instruments are widely used in China, India, Pakistan, the US, and other countries.