The open-channel flowmeter floats on the water’s surface by using the buoyancy of the water. The distance from the liquid level to the silt and from the liquid level to the open channel baffle is obtained by ultrasonic distance measurement. At the same time, the velocity of water flow is measured by ultrasonic velocity measurement, so as to further calculate the outflow.
In daily life, the measurement of each parameter of the open channel is of guiding significance for people to understand the ponding situation in the measured area. However, due to the sediment in the water, there will be silt accumulation at the bottom of the open channel, which makes the flowmeter have a deviation in the flow measurement. At present, the open channel flowmeter on the market cannot accurately measure the flow of an open channel in real time when there is silt at the bottom of the open channel.
Fig. 1 Structure of acquisition board
Fig. 2 Overall Structure Diagram
Figure 2 shows the overall structure diagram, including the core control board, acquisition board, wire, and open channel baffle. Figure 1 shows the structure diagram of the acquisition board, including the floating board, fixed nodes, two ultrasonic ranging modules, and one ultrasonic Doppler velocity measurement module. Here, the fixed node is at the front end of the triangular floating plate, and two ultrasonic ranging modules are respectively fixed at the left and right ends of the floating plate in opposite directions. The transmitting and receiving probes of the ultrasonic Doppler velocity measurement module are also placed at the left and right ends of the floating plate. When the floating plate floats on the liquid surface, the transmitting and receiving probes of the ultrasonic Doppler velocity measurement module are located below the liquid surface.
After the core board sends the acquisition signal to the acquisition board through the wire, the acquisition board floating on the liquid surface starts to collect. The acquisition board measures the height from the liquid surface to the open channel baffle (h1) and the height from the liquid surface to the sludge (h2) respectively through the ultrasonic distance measuring probe fixed on the upper and lower sides of the acquisition board. At the same time, the ultrasonic Doppler velocity measurement module measures the water flow velocity (v) in the open channel. The measured parameters are transmitted to the core control panel through wires.
The core control panel calculates the thickness of the sludge (h-h1-h2) according to the distance (h) from the open channel baffle to the bottom of the open channel, the height (h2) from the liquid level to the sludge, and the height (h2) from the liquid level to the sludge, the width (L) of the open channel, and the flow velocity (V) of the open channel.
Preliminary preparation: measure the distance (h) and width (L) of the open channel from the baffle plate to the bottom of the open channel in advance. Since the values of parameters such as the size and height of the open channel are fixed, it is unnecessary to repeat the measurement.
The flow in the open channel provided in this paper is floating on the water surface, so it can effectively prevent the probe from being blocked due to sludge accumulation, or inaccurate measurement due to the elevation of the sludge accumulation water surface, and it can also indirectly measure the mud level.