LS20B type propeller flowmeterDetailed product description：

The LS20B propeller type current meter is a general instrument for measuring the flow velocity in hydrological tests. It is used to measure the average flow velocity of a predetermined measuring point in the water section of rivers, lakes, reservoirs, canals and other rivers, and can also be used to measure the flow velocity in pressure pipelines and some scientific experiments.
The LS20A rotary propeller flowmeter complies with relevant national standards such as GB/T11826-2002 "Rotary flowmeter".

Widely applicable to hydrological testing, water conservancy investigation, farmland irrigation, runoff experiments, etc., it can also be used for monitoring flow velocity or flow in industries or departments such as hydropower, environmental protection, mining, transportation, geology, scientific research institutes, and municipal government.

2 Main technical performance and parameters
1) Rotating diameter of propeller: Φ 125mm
2) Spiral propeller hydraulic pitch b: 200mm (theoretical value)
3) Starting speed v0:0.03m/s
4) Critical speed vk: about 0.13m/s (subject to actual verification value). According to statistical analysis, vk is much smaller than the above value
5) Speed measurement range: 0.05m/s to 15m/s
6) Output signal: Magnetic switch contact on/off signal
7) Number of signals/rotor speed: 2/1 (2 signals per 1 rotation)
8) Switch contact capacity: DC U ≤ 24V I ≤ 120mA
9) Contact operation times: 1 × 107
10) Relative mean square error of the entire line m: | m | ≤ 1.5% (for v ≥ vk)
11) Relative error δ: | δ | ≤ 5% (used when v12) Working water environment: water temperature 0 ℃~+40 ℃, water depth 0.2m~50m, suspended sediment concentration ≤ 50kg/m3
13) Storage environment: Temperature -25 ℃~+55 ℃ Humidity ≤ 90%
3. Structural features and working principle: The LS20A rotary propeller flowmeter consists of a rotary propeller, rotating components, body frame components, tail wing (or tail cone), etc. (see Figure 1).
Spiral paddles are used to passively sense water flow and rotate around a horizontal support axis under the driving force of water flow. Its rotational diameter is Φ 125mm, and the theoretical hydraulic pitch (mechanical lead) is 200mm.
The rotating component (see Figure 2) consists of a support system (see Figure 3), a sealing system (see Figure 4), and a magnetic excitation signal generation and transmission system (see Figures 5 and 6). Used to generate a certain angular velocity and magnetic excitation signal under the pushing force of the propeller.
The body frame components participate in signal transmission and are used for installation and fixation during the operation of the flowmeter, with an installation aperture of Φ 20mm.
The tail fin is used for orientation and balance during the operation of the flowmeter.
When the flowmeter is working, the propeller is driven by the water flow to rotate, which drives the rotor part of the rotating component to rotate synchronously. Two magnetic steels installed on the rotor excite the reed switch to generate on/off signals.
In the installation of hydrological tests, there are generally several installation methods for flow meters (see Figure 7, Figure 8, Figure 9, Figure 10), for reference only:
(1) Installation of measuring rod
When measuring shallow water flow, CG20-1 measuring rod can be used for installation. The total length of the measuring rod is 3m, with each section measuring 1m. There is a marking line every 2cm on the measuring rod, and a number mark every 10cm, which serves as a marker for the installation position of the depth and velocity meters. There is a pointer (compass) above the measuring rod to align the flowmeter with the flow direction. When the flow rate is high, tail fins should be installed to ensure accurate orientation and stability of the flow meter; When the water is shallow and the flow velocity is low, a tail cone can be used instead of a tail fin.
Note that CG20-1 measuring rod is an accessory for product selection.
(2) Suspension installation
1) When the flow velocity is less than 1m/s, the shaft suspension installation method can be used (the weight of the lead fish should not be less than 30kg).
Note that the rotating shaft components, connecting rods, rope hooks, etc. are accessories for product selection.
2) When the flow rate is 1m/s to 3m/s, the suspension rod suspension installation method can be used (the weight of the lead fish should not be less than 50kg).
The suspension rod (including suspension rod screws and split pins) is an accessory for product selection.
(3) Installation of lead fishing rod
When the flow velocity is greater than 3m/s and the water depth is greater than 10m, the installation method of lead fishing rod can be selected. At this time, heavy lead fish weighing over 100kg should be equipped to reduce the suspension angle.
To ensure the stability of the flowmeter when it enters the water, a thin rope can be connected to the suspension cable from the tail wing traction screw.
The suspension components are optional accessories for the product.
The use, operation, and maintenance of the flow meter should strictly follow the relevant provisions of SL443-2009 "Hydrological Cableway Measurement Specification", GB50179-93 "River Flow Measurement Specification", and other relevant hydrological measurement specifications.
Before using the flowmeter, the following simple tests should be conducted:
(1) Sensitivity testing
1) Aim the propeller at the water facing surface and blow gently and evenly. The propeller should be able to start and turn easily without any jamming;
Note that this test largely depends on the user's actual experience and should be repeatedly tested and mastered proficiently for future comparison.
2) Quickly turn the propeller by hand and there should be no emergency stop phenomenon.
(2) Signal testing
Use counters, speakers, multimeters, etc. for testing, and the signal should be accurate and reliable.