Electricity + Control March 2021

MEASUREMENT + INSTRUMENTATION

device to the internet server. The data can be transferred directly to the processing goods management system.

At a glance 

In mobile silos used to transport raw materials from manufacturer to consumer, regular updates on the location and fill level of the silos is key in optimising a stable supply chain.  In such circulation systems, the smart level sensor becomes the intelligent control unit of the silo tank.  LPWAN technologies ensure low energy consumption in battery-powered sensors and a long detection range for radio signals.

LoRaWAN in fill-level sensors The advantages offered by LoRaWAN convinced Pepperl+Fuchs to integrate this technology into the WILSEN.sonic.level battery-operated wireless fill-level sensor. The sensor measures the distance to the filling material using ultrasound and calculates a fill level for the container. The payload to the network server contains not only the distance and fill level, but also the GPS coordinates as well as the temperature and condition of the battery. In the sensor, the times for data transmission can be set within certain limits. These limits range from once a minute to once a day. More frequent transmissions affect the battery life, but enable the exact movement profile of a mobile container to be determined. Longer transmission intervals with just a few transmissions per day extend battery life by several years. Optimising the logistics process With the current fill level and geo-position, WILSEN.sonic. level operates as an intelligent component to offer a silo tank important information for replenishment logistics. After the filling process at the site of the granule manufacturer, the silo can confirm the exact filling quantity in the purchase order and authorise its collection at the site of the logistics company. The driver will be notified of the exact pick-up location. The movement profile along the transport route enables the injection-moulding company to calculate the exact time of delivery. Once the silo has been unloaded by the logistics service provider, the silo will automatically inform the injection-moulding company’s intralogistics system which ramp it is on. From this point on, the intralogistics system always knows the exact location of the silo on the site, even if it has been put into and removed from storage several times. Each time product is removed from the silo, the silo provides data on the remaining quantity and can independently issue a command to be refilled when a minimum quantity is reached. Once the silo is completely empty, it informs the logistics provider of its pick-up location. Optimising intelligent logistics beyond the borders of a company in such a way requires a comprehensive wireless network. For LoRaWAN, this is already the case in some European countries, with others expected to follow. □

Operating as an intelligent component the sonic level sensor provides key information to support efficient replenishment logistics. LoRa signals can be transmitted easily from the basement of a building. In open spaces, they bridge distances of 15 to 40 km and are therefore equally suitable for indoor and outdoor applications. The LoRa field device sends its signals to a LoRa gateway, which in turn forwards them to a network server. A particular advantage of LoRaWAN technology is that the field devices do not log on to the gateway but only to the network server behind it. Therefore, gateways operate only as converters between the wireless and the wired world. This system architecture makes the wireless system more rugged, as the data of a field device is simultaneously received via several gateways or channels and forwarded to the network server. Only the server decides on which specific data path it will use for signal evaluation. This procedure ensures valuable redundancy in signal transmission, and facilitates network setup. It means that if the reception quality is insufficient, the network can easily be compressed via other gateways without having to create a new network plan to check the radio coverage. Furthermore, the wireless system requires only a few gateways, as a gateway can communicate with around 2 000 field devices at the same time and provide visibility over an area of five to seven square kilometres. Regarding data security, LoRaWAN offers end-to-end encryption of the sensor data as it travels from the field

For more information visit: www.pepperl-fuchs.com/southafrica

20 Electricity + Control MARCH 2021