Level monitoring is an Internet of Things application for multiple industries, often with many different applications in a given location. It’s a powerful tool for improving performance, lowering costs, and increasing safety. However, making the right choices for solution components takes some research and expertise.
Virtually any substance is a candidate, including liquids, pastes, grains, chemicals, and powders. Closed containers such as silos, vessels, and tanks, as well as open environments like ponds or stock tanks, can be monitored. Many environments also have good potential opportunities for automation, triggering things like shutoff or replenishment.
The most common requirement is continuous level monitoring, capturing and transmitting data regularly to provide real-time measurement for analysis and action. Some implementations, however, only require a “report-by-exception” approach notifying when a sensor detects attainment of a predefined level (typically when a container is full, needs filling, or is in danger of overflowing).
Level monitoring is important to multiple industries, including:
- Agriculture
- Oil & Gas
- Water Management
- Wastewater Management
- Waste Management
- Manufacturing
- Mining
- Construction
- Food & beverage
There is more than one option for the sensing technology, including:
- Radar
- Laser
- Ultrasonic
- Hydrostatic Pressure
- Capacitive
- Radiometric
For some of these, like radar, laser, and ultrasonic, levels are measured based on a concept known as “time of flight.” A sensor located above the maximum level of the substance takes a reading using a calculation based on the time it takes for a pulse from the sensor to make a round trip to the surface of the substance and back. Others, like hydrostatic pressure, use a sensor immersed in a liquid connected to an external device to determine the result.
There is a long list of critical factors that drive the choice of sensing technology. Certain types are only for liquids, and even only for certain types of liquids. Others perform better for bulk solids than liquids, even though they may be used for either. Extreme temperature or humidity environments can also make a particular type a better option. Containers like silos often have a large amount of dust in the air, where some sensors work better than others at obtaining accurate readings. Corrosive liquids like chemicals, wastewater, and acid may require particular submersible types specifically designed for harsh conditions.
Many monitoring sites are in remote areas, difficult-to-reach spots, or locations with safety concerns where wireless connectivity makes sense. Low-power wide-area network options (LoRaWAN or NB-IoT, for example) work well for these kinds of applications, where small packets of data are transmitted as infrequently as a few times daily. The devices for these technologies are often battery-powered and can last for years on a single charge. Satellite connectivity is also an option, with recent advances making satellite more accessible and cost-effective than it has been in the past.
One device can also be outfitted with multiple sensors, often with minimal impact on battery life. Combining level sensing with other types, such as pressure, temperature, and electrical conductivity, provides even more valuable information. And for “containers that move”, such as trucks, trailers, or pallets, location-reporting sensors like GPS are common.
As with any IoT solution, all components must be carefully selected to meet the requirements, environmental conditions, accuracy needed, etc. Poor visualization, limited alerting capability, the wrong network technology, and a host of other issues can render the application useless, so proper planning is essential.