2.2. Construction of the Sand Collector

The core structures of the sand sampler (Figure 2) were a dust collection system and a dust measurement system. The dust collection system was installed above the device enclosure (components 1–6 in Figure 2), which mainly consisted of an empennage, first air leakage network, second air leakage network, sand intake, hollow shaft, and bearing dust proof seat. The static measurement system was in the device enclosure, which was mainly composed of a small-range, high-precision dust weighting system and a large-scale dust weighting system. The small-range, high-precision dust weighting system consisted of an automatic sand release device and a small-scale, high-precision weighing sensor. The small-scale, high-precision weighting sensor was mounted on the inner wall of the device enclosure, and the automatic sand release tipping bucket was related to the small-scale, high-precision weighting sensor. The automatic sand release device consisted of a small-capacity container (tipping bucket) and a container support shaft. The small capacity container and container support shaft were related to a flexible rod, which can rotate around the support shaft. The large-scale dust weighting system consisted of a large capacity container and a large-scale weighting sensor. The large capacity container was mounted on the second platform. One end of the large-scale weighting sensor was fixed under the second platform and the other end was fixed on the inner wall of the device enclosure. Conveniently, the large-capacity container was designed as an inverted truncated cone-shaped container, which could help concentrate the center of the gravity of the collected objects to the sensing part of the weighting sensor.

Structure diagram of the fully automated high-precision sand collector: 1. empennage; 2. first air leakage network; 3. second air leakage network; 4. sand intake valve; 5. hollow shaft; 6. bearing dust proof seat; 7. small-capacity container; 8. container support shaft; 9. large-capacity container; 10. small-range, high-precision weighing sensor; 11. large-scale weighing sensor; 12. first triangular plate; 13. second triangular plate; 14. first rectangular plate; 15. second rectangular plate.

To improve the measurement accuracy and range of the sand sampler, graded weighting was adopted. The range of the first-grade weighting container was 0–300 g with an accuracy of 20 mg, and the range of the second-grade weighting container was 0–10 kg. Sampling was carried out with the created device for twelve months at the test site, and automatic observations were realized, where an aspect sensor was used to monitor the sand amounts arising from each direction. The data acquisition system had a high storage capacity (2 GB) and high frequency (≥1 Hz), which allowed us to dynamically and comprehensively record the processes and dynamic variations of dust emission arising from wind erosion in real time and weigh the collected dust with high precision over a wide range.

During the tests, the empennage kept the sand intake rate consistent with the wind direction according to the wind force in the wind direction. At this point, the surface sands entered the hollow shaft through the sand intake valve. Sand-carrying gas flows could be discharged from the first air and second air leakage networks. Sands then automatically sank to the small-capacity container via gravity, and the sand weighting sensor began to sense (accuracy: 20 mg). The weight data were subsequently uploaded to the data acquisition system. Then, the aspect sensor uploaded the aspect data of the acquired sand to the data acquisition system to obtain the instantaneous sand amount in the corresponding direction. If the collected sands were over 240 g, the tipping bucket rotated automatically to pour the sands into the large-capacity container for weighing (weight range: 0–10 kg). Not only was the total sand amount in the whole process recorded, but also the data measured by the small capacity sensor were calibrated, realizing long-term automatic monitoring, and reducing the manual workload. The data acquisition system was connected to a GPRS/CDMA communication module and power supply system, and the GPRS/CDMA communication module was wirelessly connected with the computer, with which real-time online observations were achieved offsite or onsite. The observation frequency was up to 10 Hz. All the data measured during an experiment, including wind speed, wind direction, sand transport aspect, instantaneous aspect sand flux, profile sand flux, and cumulative total sand flux, were uploaded to the data acquisition system. Through the wireless transmission network, the backstage carried out real-time remote automatic monitoring of the acquired data.