● Instrument composition

The testing device consists of a vertical sand guide tube, a calibration funnel, a filter screen, a sample rack, and a sand collector.

● Main parameters
Sand guide pipe: It can be composed of a solid wall plastic pipe with an inner diameter of not less than 150mm and a smooth inner wall, with a length of 2850mm. The non perpendicularity of the sand guide pipe is not greater than 0.2 °.
Calibration funnel: The upper opening size of the calibration funnel is 120mm × 40mm, with a height of 100mm and a four sided slope angle of 45 °. The four sides of the upper mouth should be straight and sharp, ensuring that the sand falling on the edge of the mouth does not change direction when it falls into the bucket. The function of this funnel is to ensure that the sand directly falling into the mouth does not deviate from the ground and impacts the protruding road sign as vertically as possible, while the sand falling out of the mouth is deviated outside the bucket and cannot impact the protruding road sign. The calibration funnel should be able to move up and down, left and right, and forward and backward, making it easy to adjust the amount and uniformity of sand passing through the funnel.
* Filter screen: The filter screen is located at the upper part of the sand guide tube, with a standard mesh size greater than 850 μ m. The function of this filter is to establish the starting point of sand falling and to limit the flow rate of sand falling. The distance between the falling sand and the grid should not exceed 30mm.
Sample holder: used to firmly hold the tested sample, keeping the base surface of the sample perpendicular, and conveniently aligning the sample with the sand guide tube and calibration funnel. It can freely adjust the height of the tested sample to keep its upper edge no more than 150mm from the upper opening of the funnel, and can adjust the horizontal direction to make the front edge of the bottom edge of the sample's reverse reflection surface parallel to the long edge of the funnel. The sample rack should not obstruct the free flow of falling sand.
Collector: A 300mm x 500mm enamel tray or other container can be used. Objective: To collect sand outside the calibration funnel.