Bill Greer, senior product specialist, Contemporary Controls
Various networking technologies specify that stations must be separated by some minimum distance. Occasionally a customer is surprised about the lack of a minimum length requirement for their Cat 5 cable that connects one Industrial Ethernet device to another.
Network cable minimum length specifications arise because of an impedance mismatch between elements in the signal path. When electrical energy is transmitted through a cable, some of it is not absorbed by the receiving station and is instead 'reflected' back to the source. This reflected energy disturbs the purity of the signal - and if the effect is of sufficient magnitude, the signal can be degraded to the extent that its information is corrupted or even useless. If source and destination transceiver impedances match the impedance of the cable itself, there is no reflected energy and signal energy is delivered completely.
Reflected signal is always an issue in a bus topology because only the end devices have transceiver impedance values that match the impedance of the cable. Mid-bus device transceivers must have higher impedance values to avoid 'loading' the cable (preventing proper signal delivery to devices further along the bus). Thus, a mid-bus device transceiver presents an impedance mismatch to the cable and inevitably creates some degree of reflected energy. To keep the reflected energy to acceptable levels, a bus protocol will specify a minimum length of cable that separates two bus devices.
Industrial Ethernet uses a star topology in which devices exist only at each end of a cable. With this topology, both transceiver impedances match the cable impedance and no appreciable signal reflection occurs. This lack of signal reflection is true whether the devices are separated by 100 m or 100 mm. Therefore, there is no need to specify a minimum cable length.
From idea to intelligent product TRX Electronics
Computer/Embedded Technology
Mouser Electronics has announced a new eBook in collaboration with Arduino – From Blink to Think: How Arduino UNO Q Helps Designers Go from Idea to Intelligent Product.
Read more...Think Diamond Long-life COM-based SBCs Electronic Products Design
Computer/Embedded Technology
A COM-based SBC combines the flexibility of a standard computer-on-module (COM) with a baseboard offering additional I/O, expansion sockets, power supplies, and I/O connectors. The result is a highly flexible, highly expandable, feature-dense product that can be adapted to the widest range of applications, offering maximum product lifetime.
Read more...Next-Gen Min-ITX motherboard Vepac Electronics
Computer/Embedded Technology
Adding to AAEON’s extensive industrial motherboard portfolio, the Next-Gen MIX-Q870A1 is the company’s most advanced Mini-ITX board to date.
Read more...Rev 2.0 PolarFire FPGA ethernet sensor bridge Altron Arrow
Computer/Embedded Technology
Smaller, multi-camera platform enables scalable Ethernet architectures for NVIDIA Edge AI systems, while lowering power, cost and integration complexity.
Read more...Intelligent video processing Rugged Interconnect Technologies
Computer/Embedded Technology
The CHARM150AGX is based on a NVIDIA AGX Orin embedded processor, which incorporates a multicore ARM processor and powerful AI/ML accelerator.
Read more...Nordic expands nRF Cloud with firmware vulnerability scanning RF Design
Computer/Embedded Technology
nRF Cloud identifies vulnerabilities in firmware and shows exactly which deployed devices are affected, empowering device manufacturers to address EU Cyber Resilience Act requirements.
Read more...Arrival of the Epic-PTH9 Vepac Electronics
Computer/Embedded Technology
AAEON introduces the EPIC-PTH9, a compact 4-inch industrial single-board computer powered by Intel Core Ultra Series 3 (formerly Panther Lake) processors.
While every effort has been made to ensure the accuracy of the information contained herein, the publisher and its agents cannot be held responsible for any errors contained, or any loss incurred as a result. Articles published do not necessarily reflect the views of the publishers. The editor reserves the right to alter or cut copy. Articles submitted are deemed to have been cleared for publication. Advertisements and company contact details are published as provided by the advertiser. Technews Publishing (Pty) Ltd cannot be held responsible for the accuracy or veracity of supplied material.
printer friendly version