Three considerations for selecting Ethernet for harsh industrial environments
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Since its introduction, Ethernet has grown by leaps and bounds and is now widely used in the commercial and enterprise markets. With its well-defined standards and ease of deployment, it is only natural that Ethernet has spread widely in the industrial world. However, meeting the requirements of Ethernet in harsh industrial environments still requires a lot of insight and effort.
As shown in Figure 1, industrial environments are completely different from commercial environments and present their own set of challenges. Industrial environments often include many harsh conditions, such as higher temperature ranges and voltages, greater noise, mechanical stress, etc. The industrial-grade Ethernet physical layer (PHY) must meet the requirements of the Ethernet protocol. In this article, I will briefly describe the three most important factors to consider when selecting an Ethernet physical layer for your system.
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Figure 1: Modern industrial setup with wireless and wired connections including Ethernet
1. Low latency . Latency is the time it takes for a packet to travel from source to destination. Different parts of the network will contribute to the total network latency. Communication in industrial networks is time-critical, which means using the lowest latency and highest determinism. Higher latency and different packet arrival times will degrade system performance.
Standard Ethernet is nondeterministic. The IEEE 802.3 standard does not specify a maximum latency number for the Ethernet physical layer. However, for Ethernet transceivers in industrial environments, it becomes very important to have low and deterministic latency. Low and deterministic latency enables faster response times and more predictability. Low latency allows applications to run faster because there is less waiting time for information to propagate through the network, while high deterministic latency improves synchronization of different networks by keeping the latency constant.
2. EMI/EMC reduction. Electromagnetic interference (EMI) is electromagnetic energy generated unintentionally by a system. Electromagnetic compatibility (EMC), on the other hand, refers to the ability of a system to operate in an environment where other systems generate electromagnetic energy. Electromagnetic interference (EMI) and electromagnetic compatibility (EMC) are important parameters in industrial environments because they may have multiple sources of electromagnetic energy. Systems with poor EMI resistance will radiate a lot of energy, which will disrupt nearby sensitive devices and reduce efficiency because energy is wasted in radiation. Designs with poor EMC can make the system highly sensitive and cause performance issues. The performance of systems with poor EMC design will be affected by other typical radiation sources, such as Wi-Fi, mobile phones, etc.
There are different EMI/EMC standards, such as the European Committee for Standardization (EN), the International Special Committee on Radio Interference (CISPR), the Federal Communications Commission (FCC), etc., which vary by region and intended market. Equipment must meet the requirements specified in these standards before it can be certified for use. These standards vary depending on the final application of the equipment. EMI/EMC standards for the industrial market are more stringent than those for the commercial market.
3.ESD protection. Electrostatic discharge (ESD) is an electrical current that suddenly enters a system through contact with a charged body. ESD events are short, but they can inject a lot of energy into the system. If the device is not designed to withstand such events, the results are likely to be devastating to the device, often resulting in the destruction of the device. Since electrostatic discharge does not always leave obvious signs of damage, it can be difficult to find damaged devices in complex systems. As such an important parameter, ESD standards have been developed so that devices must meet their minimum requirements according to their final application, such as the International Electrotechnical Commission (IEC) 61000-4-2. Similar to EMI/EMC, ESD requirements for the industrial market are more stringent than those for the commercial market.
Industrial-grade Ethernet physical layers should have low deterministic latency, comply with stringent EMI/EMC standards, and be immune to ESD events. TI's Ethernet portfolio is designed to meet these requirements and has been put into use in many harsh industrial environments around the world, including devices such as the DP83867 Gigabit Ethernet PHY customized for harsh industrial environments and the DP83826E low-latency 10/100Mbps Ethernet physical layer.
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