As the core equipment for testing the waterproof performance of products, the accuracy of flow measurement in the rain test device directly affects the reliability of the test results. According to the GB/T 4208-2017 standard, flow control needs to be precise to 0.07L/min per nozzle (IPX3/IPX4 level). This article analyzes the entire process of flow measurement from equipment calibration, parameter adjustment to data verification.

　　1、 Equipment calibration and flow calculation

1. Flow calibration: Use high-precision flow meters (such as glass rotor flow meters) to calibrate each nozzle of the swing tube. Taking IPX3 level as an example, a device with a swing tube radius of 400mm needs to ensure a total flow rate of 0.84L/min (12 holes x 0.07L/min) for 12 spray holes.

2. Pressure matching: Stabilize the water pressure within the range of 80-100kPa through a booster pump to avoid flow deviation caused by pressure fluctuations. A certain model of test box adopts a variable frequency water pump to achieve a flow stability of ± 1%.

3. Spray hole distribution: IPX3 level requires spray holes to work within 60 ° arc segments on both sides of the midpoint of the swing pipe, covering a total of 12 holes; The IPX4 rating is extended to 90 ° arcs on both sides, with a total of 18 holes. The spacing between spray holes should be strictly arranged according to the standard of 50mm.

　　2、 Measurement process and parameter adjustment

1. Sample installation: Place the test sample at the center of the swing tube, adjust the lifting platform so that the top of the sample is ≤ 200mm away from the spray nozzle. For example, when testing car lighting fixtures, ensure that their outer shell is exposed within the spray range.

2. Flow regulation: Rotate the flowmeter valve counterclockwise to the maximum opening and observe the real-time flow rate through the float scale. The IPX3 level requires the flow rate to be adjusted to 1.1L/min (including redundant design), while the IPX4 level needs to be increased to 1.7L/min.

3. Dynamic monitoring: After starting the water pump, record the flow meter reading every 2 minutes. If the flow fluctuation exceeds ± 5%, it is necessary to check whether the spray hole is blocked or whether the water pump frequency is stable.

　　3、 Data validation and error correction

1. Flow verification: Use a measuring cup to collect the water output of the pendulum tube for 1 minute, and compare the flow meter reading. For example, the theoretical water output of IPX3 level should be 1.1L, and the measured value should be within the range of 1.045-1.155L.

2. Error correction: If the flow rate is low, the worn nozzle (standard aperture 0.4mm) can be replaced or the filter screen can be cleaned; If the flow rate is too high, it is necessary to adjust the frequency of the water pump or add a throttle valve.

3. Environmental compensation: In low-temperature environments (such as 5 ℃), the water flow rate needs to be increased by 3% -5% to compensate for viscosity changes. According to data from a certain laboratory, for every 10 ℃ decrease in water temperature, the flow rate needs to be compensated by about 2%.

The flow measurement of the swing pipe rain test device needs to be combined with equipment calibration, parameter adjustment, and dynamic verification to ensure compliance with IPX3/IPX4 level standards. It is recommended that operators regularly participate in professional training to master the skills of using flow meters, and establish equipment maintenance records to record the replacement cycle of spray holes and the operation time of water pumps. In the future, with the application of IoT technology, intelligent traffic monitoring systems will achieve real-time alarm and automatic calibration, further improving testing efficiency and accuracy.