Silos are Going Digital – Sensors to Provide Accurate Level Measurement
Monitoring Bulk Materials is Challenging
Checking the stock levels of such large containers often involves climbing the side of the container and measuring the stock level from the top, which puts workers at risk of falling. It is of high priority to make routine processes like level measurement as safe as possible, particularly in the agriculture industry, which has one of the highest rates of work-based fatalities. Furthermore, manual stock checks are not only time-consuming but also inaccurate.2
Accurate Level Measurement is Essential for Safe and Efficient Operation
Accurate level measurement sensors are used in digital systems to detect how much stock is remaining in a silo. However, automatic measurements are challenging in silos, as levels are often uneven with irregular build-up and lots of dust.
A Range of Sensors are Available for Accurate Level Measurements
Traditional mechanical stock measurements are cheap and straightforward, yet they have several drawbacks. Frequent maintenance is required for moving parts and they can quickly wear out, particularly in dusty silo environments. Contamination is also a concern in many industries, particularly the food industry, meaning that contact between the probe and the material is undesirable. 5
Ultrasound sensors are used in many newer stock monitoring solutions. The sensors send ultrasound waves at the material in the silos and detect the reflected signal. It is then possible to calculate the distance between the material and the sensor. Optical and radar sensors work similarly, and both provide alternative solutions. If the stock levels are distributed unevenly, then multiple sensors can be used to give a 3D surface mesh of the material. 5,6
Continuous level monitoring can be achieved with ultrasound sensors and these do not have the drawbacks of contact and maintenance of moving parts. However, the signal can bounce around, causing less accurate readings of content volume.
Most affordable ultrasound sensors below the 100 EUR price tag are unsuitable for large storage units as they only provide a limited range of approximately 7-8 m. Alternative sensors are available such as those using lasers, but these are expensive and have high power consumption, limiting their compatibility with battery-powered systems. 5,6,7
Time-of-Flight (ToF) Level Measurement Sensors Provide Unrivaled Accuracy
ToF sensors work by sending pulsed infrared light at the material surface and detecting the reflected light. The sensor measures the time taken for light to travel to and from the material. The distances to the surface of the material can be calculated from these measurements.8,9
At a competitive market price, ToF sensors can optimize stock delivery and storage, increase automation, improve efficiency, and reduce operating costs.
Terabee are the ToF experts
Sensor modules provided by Terabee can integrate with existing frameworks. Rapid prototyping projects and integration work for volume production are enabled with the available interfaces, which include USB, UART, and I2C. Fast connectivity to manufacturing systems is possible with industrial interfaces like RS-485.
Terabee level measurement sensors can be used in battery-powered devices and other low-energy solutions as they have low power requirements compared to laser ToF sensors. Terabee is committed to working together with customers to optimize solutions to meet their needs. As such, Terabee ToF technology can be deployed in a plug and play manner and easily customized.
Terabee can also build complete solutions on top of raw sensor data for customers who require the development of new level measurement applications.
References and Further Reading
2. ‘Global Estimates of Occupational Accidents and Work-related Illnesses 2017’ — Hämäläinen P, Takala J, Kiat TB, Workplace Safety and Health Institute, 2017.
3. ‘Smart feeding in farming through IoT in silos’ — Agrawal H, Prieto J, Ramos C, Corchado JM, Intelligent Systems Technologies and Applications, 2016.
4. ‘What’s new in smart weight-and-cable bin level sensors’ — Lewis J, Powder and Bulk Engineering, 2006.
5. ‘Sensor Technology Handbook’ — Wilson JS, Elsevier, 2005.
6. ‘Level sensing of liquids and solids ‐ a review of the technologies’ — Hunt JA, Sensor Review, 2007.
7. ‘Time-of-flight level monitoring for silos, water and more’ https://www.terabee.com/time-of-flight-level-monitoring-for-silos-waste-and-more/
8. ‘An Overview of Depth Cameras and Range Scanners Based on Time-of-Flight Technologies’ — Horaud R, Hansard M, Evangelidis G, Ménier C, Machine Vision and Applications, 2016.
9. ‘Time of Flight Principle’ https://www.terabee.com/time-of-flight-principle/
10. ‘TeraRanger Evo 60m’ https://www.terabee.com/shop/lidar-tof-range-finders/teraranger-evo-60m/
11. ‘TeraRanger Evo 3m’ https://www.terabee.com/shop/lidar-tof-range-finders/teraranger-evo-3m/