Open channel flowmeter is a system monitoring device that measures fluid flow in open channels or channels. It is suitable for flow measurement of rectangular, trapezoidal open channels and culverts such as reservoirs, rivers, water conservancy projects, urban water supply, sewage treatment, farmland irrigation, water administration and water resources.
Types of open channel flow meter
According to different measurement principles, the open channel flow measurement flow meter have ultrasonic open channel flowmeters, Doppler open channel flowmeters, and open channel radar flowmeters. They are all open channel flowmeter monitoring systems.
Open channel flow meter working principle
The working principle of ultrasonic open channel flowmeter:
Using the open channel technology, based on the flow velocity-water level algorithm, by measuring the fluid level height, combined with the geometric dimensions of the standard weir and groove, slope coefficient, channel accuracy, hydraulic ramp, flow velocity vertical plane correction coefficient, and then through the internal measurement of the instrument The microprocessor calculates the flow. Due to the non-contact measurement, open channel flowmeters can be used in harsh environments. Under the control of the microcomputer, the open channel flowmeter transmits and receives ultrasonic waves, and calculates the distance between the open channel flowmeter and the measured liquid level according to the transmission time, so as to obtain the liquid level height. The liquid flow Q can be finally obtained according to the calculation formula.
The working principle of Doppler open channel flowmeter:
The contact measurement method is used, the sensor is placed at the bottom of the channel, and through the velocity-area method, between the two probes, the system calculates the flow velocity of the passing water according to the Doppler time effect, and then passes through the area where the sensor is located. The cross-sectional area is converted into the instantaneous flow according to the formula.
fd=2f/c*v*cosθ
fd: received frequency f: transmitted frequency c: ultrasonic velocity θ: angle between water flow and incident wave
How Radar Open Channel Flowmeter Works
The radar open channel flowmeter is made by the principle of Doppler effect. When working, electromagnetic waves are generated to the water surface, and the electromagnetic waves will be scattered when encountering the moving water surface and form an echo. Because the received echo frequency has a certain deviation relative to the transmitting frequency. The water surface velocity can be obtained from the Doppler frequency equation, and a moving target will generate a low-frequency output signal at the radar sensor. The frequency of this signal depends on the moving speed, and the amplitude depends on the distance, reflectivity and size of the moving target. The Doppler shift is proportional to the speed of motion. The system of fixed-point radar flowmeter can be connected to multiple radar probes, which is equivalent to laying multiple measuring vertical lines, and calculating the cross-sectional flow according to the cross-sectional parameters.
What is the open channel flowmeter advantages?
The open channel flowmeter is different from other closed full-pipe flowmeters. It is a flowmeter with free surface natural flow in a non-full pipe state or an open channel. The open channel flowmeter based on the open channel principle is cheap and easy to use, so it is widely used in open channel flow measurement.
Application of Ultrasonic Open Channel Flowmeter
The ultrasonic open channel flowmeter consists of an ultrasonic probe for measuring liquid level and a flow calculation transmitter. According to the different structure, it can be divided into integrated type and split type. It is suitable for measuring the flow of rectangular, trapezoidal and U-shaped open channels such as reservoirs, rivers, water conservancy projects, urban water supply, sewage treatment, farmland irrigation, water administration and water resources.
Installation of Ultrasonic Open Channel Flow Meters
Ultrasonic open channel flowmeters need to be measured with weirs and grooves. Commonly used weirs and grooves include Parshall grooves, rectangular grooves, triangular weirs, etc. The appropriate matching method can be selected according to different site environments. When the flow rate is 40 L/S, use Parshall trough or rectangular weir for measurement.
Application of Doppler Ultrasonic Flowmeter
The Doppler ultrasonic flowmeter uses the physical principle of Doppler frequency shift to measure the speed of water flow. Therefore, the Doppler ultrasonic flowmeter is suitable for measuring fluids containing solid particles or bubbles, and is not suitable for measuring pure water. The scope of use includes: natural rivers, artificial rivers, farmland channels, urban sewers, enterprise sewage outlets, sewage treatment plants, etc.
Doppler Ultrasonic Flowmeter Installation
The installation method of the Doppler ultrasonic flowmeter is as follows. During the installation process, it needs to be parallel to the direction of the water flow and raised a certain distance to prevent the influence of sludge on the measurement. In special occasions, a purging device can be selected to purge the probe sensor.
Application of Radar Open Channel Flowmeter
Radar open channel flowmeters are suitable for non-contact flow measurement in rivers, pipes, channels, etc.
Installation of Radar Open Channel Flow Meters
Can be wall mounted or hoop mounted. When installing, it can be directly fixed on the wall or bridge with expansion screws or the equipment can be fixed on the cross arm with a hoop.
Can the Ultrasonic Open Channel Flow Meter used to Measures Sewage ?
yes. Portable Doppler ultrasonic open channel flowmeter uses the principle of Doppler velocity area method to monitor flow. It is designed for flow velocity and flow measurement in open channels and partially filled pipes.
The principle of the Portable Doppler Flow Meter is to measure the fluid flow rate using the ultrasonic Doppler principle.
The liquid level is measured by pressure and ultrasonic sensors. The calculator can set multiple point coordinates to simulate the shape of the weir trough to obtain the cross-sectional area, so as to measure and monitor the flow.
How to order open channel flowmeter?
Open channel flowmeter model type order attentions:
According to the flow measurement characteristics of urban water supply diversion channels, industrial water diversion and drainage channels, and sewage treatment channels, the following factors should be considered in the selection of open channel flowmeters:
1) The size and shape of the waterway, the range of velocity, the maximum flow and the minimum flow;
2) Measurement accuracy requirements;
3) Flowmeter setting place and environmental conditions;
4) Liquid condition, cleanliness, solid phase concentration, corrosiveness;
5) Allowable drop (or raised water level) and channel slope on site;
6) Materials of instrument parts in contact with liquid;
※Note: As one of the earliest flow meter manufacturer, SenTec provide a wide variety flow measurement solutions, such as differential pressure flow meters, Calorimetric Flowmeter, liquid flow sensor, Ultrasonic Level Transmitter, mass flow meter, Variable Area Flowmeter or Rotameter, Electromagnetic Flowmeter, Turbine Flowmeter, Vortex Flow Meter, Thermal Flowmeter, Coriolis Flowmeter, Mass Flowmeters, Open Channel Flowmeters etc.
For specific open channel flowmeter price, please contact our sales engineer.
