COVER STORY
Table 1: Overview of the OSI model with its protocols and bus systems
Table 2: Overview of the different communication technologies in process automation
required with 10BASE-T1L. Through the elimination of the gateways, the costs and the complexity of these old installations are greatly reduced, and the data islands created by them are swept away. In addition, higher powers can be transmitted over the data line. For example, 500mW in intrinsically safe areas (hazardous areas) and even up to 60W in non-intrinsically safe areas can be transmitted.
Ethernet standards such as PROFINET, EtherNet/IP, HART-IP, OPC UA, or Modbus-TCP, and IoT protocols such as MQTT, can enable the easy and powerful connection of fi eld devices to the cloud. As with standard Ethernet, with 10BASE-T1L there are bridges that enable coupling of various network segments and devices. Diff erent network topologies can be realised and used to supply power to the connected devices. In process automation, switches are often connected to controllers, HMIs and the cloud. Switches allow media redundancy in the form of ring topologies for increased availability. In process automation, the connections to the devices, sensors and actuators are also called spurs, whereas connections
10 November 2022 | Automation
Table 3: Overview of power transmission levels at different cable lengths (Type 18 AWG)
between the switches and running up to the control system fall under the name trunk.
Further possibilities arise from the constantly increasing integration density of devices. For example, a 10BASE-T1L switch can be integrated into a sensor connected directly to additional sensors that can also be supplied by it. Figure 2 shows an example interconnection of diff erent switches.
Communication with a 10BASE-T1L- capable device takes place via the host processor. It usually requires an integrated MAC function, a passive media converter, or a switch with 10BASE-T1L ports.
“Two-wire” implementation The 10BASE-T1L standard not only off ers communication of data from sensors
and actuators, but also provides the possibility of supplying them with power via the signal lines. Specifi cally, 10BASE- T1L can deliver up to 60W of power in non-intrinsically safe areas. In explosion- protected (intrinsically safe) areas, the power is limited to 500mW; in this case, the signal amplitude is also reduced from that of standard applications from 2.4V to 1V, to comply with the strict requirements for maximum energy applicable there. However, as a result, only reduced transmission distances are possible in intrinsically safe areas. Table 3 provides an overview of the possible power transmission levels for the various line lengths and areas for a Type 18 AWG cable. 10BASE-T1L provides a relatively robust communication standard for
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