The ultrasonic open channel flowmeter converts water level height into flow rate value through non-contact measurement technology, and its core principle can be summarized as the precise conversion process of "measuring water level - calculating flow rate".
Water level measurement: precise detection of ultrasonic waves
The device emits high-frequency sound wave pulses to the liquid surface through an ultrasonic probe, and the sound waves reflect back to the probe after contacting the water surface. The system records the time difference (t) between the emission and reception of sound waves, and calculates the distance from the probe to the liquid surface (D=v × t/2) by combining it with the sound velocity (v) in the air. For example, if the speed of sound is 340m/s and the time difference is 0.001s, the distance is 0.17m. When installing the probe, a fixed distance (L) is preset to the bottom of the channel, and the actual water level height (H) is obtained through the formula H=L-D. This process needs to consider the influence of temperature on sound velocity. Some devices have built-in temperature compensation function to ensure measurement accuracy of ± 3mm in environments ranging from -35 ℃ to 80 ℃.
Flow Calculation: Mathematical Conversion of Hydraulic Models
After measuring the water level, the equipment calculates the flow rate based on the hydraulic characteristics of the supporting weir. Taking the Bacher trough as an example, the water flow at its throat forms a critical flow, and the flow rate (Q) is in a fixed power relationship with the throat liquid level (H), with the formula Q=K × H ⁿ (K is the flow coefficient, n is determined by the size of the trough). For example, for a Bacher groove with a throat width of 0.3m, when the liquid level is 0.5m, a flow rate of 120m ³/h can be obtained by checking the table or using a built-in algorithm. For non labeled channels, the equipment supports importing user-defined water level flow curves to achieve flexible adaptation.
Technical advantages: non-contact and high precision
This technology propagates sound waves through the air, avoiding direct contact with sewage and corrosive liquids, and solving the problem of traditional mechanical flow meters being prone to blockage and wear. The multi-channel design can synchronously monitor multiple flow rate points, combined with liquid level data, to control the measurement error within 1% -5%, meeting the strict requirements of flow monitoring in fields such as environmental protection and water conservancy.