Node & Gateway Networks
Node and gateway networks can monitor large numbers of sensors.
Nodes are wireless loggers and sensor interfaces that read sensors, digitize the readings, and send them to the gateway.
Gateways receive readings sent by the nodes, reformat them for the internet, and forward them to an internet server.
Node & Gateway networks are replacing centralized data acquisition systems.
Problems of Centralized Data Acquisition
Traditional systems deploy a centralized datalogger. Cables from all the sensors on site are connected to that logger.
The complexity of wiring and programming increases with the number and type of sensors to be monitored.
Care and expense is required to route sensor cables to the logger and away from construction machinery.
Long runs of cable, common at larger sites, are expensive to install and vulnerable to voltage drops, electrical noise, and damaging voltage transients.
Communication is not built in, so transferring data to the internet requires additional modules and programming.
Advantages of Node & Gateway Networks
Node & Gateway systems are decentralized. Multiple nodes are installed, each monitoring a small number of sensors.
Nodes are matched to sensor types and have fixed capacities, greatly simplifying wiring and programming.
Compact and self-powered, nodes can be installed close to the sensors they monitor, minimizing cable routing issues.
Wireless transmissions eliminate long runs of cable. Nodes can also be installed in locations that are impractical to connect with cables.
Built-in networking provides automatic and secure wireless communication between loggers and an internet gateway.
Types of Wireless Nodes
Wireless Loggers read sensors at specified intervals, digitize and store the readings, and then transmit them to an internet gateway. Single and multi-sensor versions are available. Typical memory capacity is more than 65,000 readings per sensor. Most loggers have a built-in barometer and temperature sensors. Battery life is 2 years or more.
Wireless Sensor Interfaces read sensors at specified intervals, digitize the readings, and then transmit them to a gateway. Single-sensor versions are most common, but multi-sensor versions are available for some sensor types. Designed for read-and-send operations, wireless interfaces can store only a few readings. Battery life is 5 to 10 years.
Wireless Sensors are loggers or interfaces that have a built-in tiltmeter, laser-distance sensor, or both. Battery life varies with reading interval, but can be 2 years or more.
Compatibility: Nodes are available for nearly all geotechnical and structural sensors.
Star and Mesh Networks
Node-and-gateway networks have replaced point-to-point radio connections. Two common configurations are star and mesh.
Star Networks: Each node transmits measurements directly to the gateway, using the industry standard LoRaWAN® protocol and sub-Ghz radio bands. The main advantages are long range, good signal penetration, and an unlimited number nodes per gateway.
Mesh Networks: Measurements are transmitted from node to node until they are received at the gateway. For best performance, each node should have line-of-sight to two other nodes. Advantages are longer battery life and the ability to reroute transmissions if a node goes off line. Gateways can handle 50 to 100 nodes.