Silos are Going Digital - Sensors to Provide Accurate Stock Monitoring

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Maintaining stock levels is a critical part of most business models. When ‘stock’ consists of large volumes of solids, powders, or liquids in large containers like silos, estimating stock levels can be challenging. Digital stock monitoring provides a cost-effective, fast, and safe alternative to manual monitoring. This article outlines the latest technologies enabling automated stock monitoring.

There is nothing more frustrating than suddenly realizing you don’t have enough stock for the coming weeks, and you need to scrabble around for emergency supplies. However, it can be equally problematic when a delivery turns up, and you have nowhere to store it because all your storage containers are full! Businesses must maintain their stock reserves at a level that ensures smooth operation but doesn’t require unnecessary additional storage. Digital monitoring and automation are quickly becoming essential to maintaining appropriate stock levels in a range of industries.1

Monitoring Bulk Materials is Challenging

In the agricultural sector, solids including grains, animal feed, corn, pellets, seeds, and oats are commonly stored in large containers such as silos, bins, or hoppers until they are ready to be used or supplied. Food, construction materials, mining products, municipal waste, recycling, plastic ingredients, and fuels are also stored in bulk using similar storage methods.

Checking the stock levels in massive storage containers like silos is not easy. It can involve climbing up huge constructions and measuring the stock level from the top, leaving workers at risk of falling. The agriculture industry has one of the highest rates of work-based fatalities, so making routine processes such as stock monitoring as safe as possible is a top priority. What’s more, manual stock checks are time-consuming and often result in data that is not quite accurate.2

Silos

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Digital Stock Monitoring is Essential for Safe and Efficient Operation

Digital stock monitoring provides reliable data so you can optimize your stock levels and deliveries, ultimately reducing storage and transport costs. Digital systems can also alert you to sudden drops in stock levels so you can identify leaks quickly and rectify the situation.3

Digital systems rely on sensors to tell them how much stock is present in a silo or container. However, levels in silos are often uneven with irregular build-up and lots of dust, making automatic measurements surprisingly challenging.

A Range of Sensors are Available for Digital Stock Monitoring

The simplest stock sensors use mechanical techniques. For example, weight and cable systems measure stock levels by dropping a probe on a cable until it touches the material in the container. It then measures the distance to the material, providing a stock level measurement.4,5

While cheap and straightforward, traditional mechanical stock measurement techniques have several drawbacks. Moving parts require frequent maintenance and can wear out quickly, particularly in dusty silo environments. Furthermore, contact between the probe and the material can be undesirable, especially in the food industry where contamination is a constant concern.5

Many new stock monitoring solutions utilize ultrasound waves. Ultrasound sensors measure stock levels by sending ultrasound waves at the material in the container and detecting the reflected signal , which allows the distance between the material and the sensor to be calculated. Other options include optical and radar sensors, which work similarly. Multiple sensors can be used to give a 3D surface mesh of stock levels when the material distribution is uneven.5,6

Ultrasound sensors provide continuous monitoring and remove some of the drawbacks of mechanical solutions, such as contact and maintenance of moving parts. However, their accuracy can be limited as the signal tends to bounce around and provide less accurate readings of  content volume. What’s more, most ultrasound sensors (below 100 EUR price tag) provide a limited range of approximately 7m, 8m so are unsuitable for large storage units. Many of the alternative sensors, such as those using lasers, are expensive and have high power consumption, limiting their compatibility with battery-powered systems, for instance. 5,6,7

Time-of-Flight (ToF) Sensors Provide Unrivaled Accuracy

Optical Time-of-Flight (ToF) sensors provide continuous, accurate stock levels, in a compact, low-cost system with no contact between the sensor and the material. ToF sensors provide long-range measurements to cover even large silos and almost do not suffer from the effects of signal bouncing or absorption. If you are looking for the latest, most accurate technology to monitor stock, look no further, optical ToF is the answer!7,8

How do ToF sensors work? They send pulsed infrared light at the material surface and detect the reflected light. The sensor measures the time taken for light to travel from the source to the material and then back to the detector. From these measurements, the distance to the surface of the material can be determined.8,9

With leading price-performance ratio in the market, ToF sensors can help you optimize your stock delivery and storage, increase your automation, improve your efficiency, and reduce your operating costs.

Terabee are the ToF experts

Terabee provides a range of ToF sensors, so no matter your requirements, they have a solution for you. For tall containers, the TeraRanger Evo 60m provides reliable long-range measurements. For smaller storage tanks, the Evo 3m sensor is the ideal solution.10,11

TeraRanger Evo 60m (left) and Evo 3m (right).TeraRanger Evo 60m (left) and Evo 3m (right).

Figure 1. TeraRanger Evo 60m (left) and Evo 3m (right).

For solution providers, consultants and system integrators with existing stock automation platforms, Terabee provides sensor modules that are ready to be integrated into existing frameworks. Available interfaces include USB, UART, and I2C, enabling both: rapid prototyping projects and integration works for volume production. Industrial interfaces like RS-485, for instance, are also available, allowing quick connectivity to manufacturing systems. What’s more, Terabee sensors have low power requirements, so you can use them in battery-powered devices and other low energy solutions. Terabee’s ToF technology bricks can be quickly customized, as the company is  committed to working together with customers to develop a solution that meets their needs and provides the data they require to keep their business running smoothly.

For customers that require a full system which is ready to manage their stock levels, Terabee can also build on top of sensor data to provide a complete customer-ready solution. Hardware and software are combined with an easy to use interface ready for controlling your sensors and analyzing stock data.

References and Further Reading

  1. ‘The Internet of Things in the Industrial Sector’ — Mahmood Z, Springer, 2019.
  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/

This information has been sourced, reviewed and adapted from materials provided by Terabee.

For more information on this source, please visit Terabee.

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