Computer/Embedded Technology


Tech update: no minimum length for Cat 5

29 November 2006 Computer/Embedded Technology

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.

More topics on Industrial Ethernet can be found at www.ctrlink.com/blog.htm.



Credit(s)



Share this article:
Share via emailShare via LinkedInPrint this page

Further reading:

First NVMe SSD Built with 8th-gen BiCS FLASH
EBV Electrolink Computer/Embedded Technology
KIOXIA recently announced the development and prototype demonstration of its new KIOXIA CM9 Series PCIe 5.0 NVMe SSDs, which incorporates CMOS directly Bonded to Array technology.

Read more...
QuecPi smart development board
iCorp Technologies Computer/Embedded Technology
The QuecPi Alpha smart MOB development board is Quectel’s smart development board based on Qualcomm’s QCS6490 high-performance 64-bit octa-core processor.

Read more...
Eskom announces PV registration extension
Computer/Embedded Technology
The South African Photovoltaic Industry Association has welcomed Eskom’s decision to extend its zero-registration fee policy and free smart meter installation for residential Small-Scale Embedded Generation customers until March 2026.

Read more...
Unlock enhanced wireless performance
Computer/Embedded Technology
Duxbury Networking has introduced Cambium Networks’ Deep Virtual Circuit (Deep VC) technology, a free upgrade for the PMP 450 platform that will transform wireless broadband performance across the country.

Read more...
Computing in industrial environments
Vepac Electronics Computer/Embedded Technology
The Panasonic Toughbook CF-33/CF33 Tablet is a 12,0-inch fully rugged device with hot-swappable twin batteries and highly configurable capabilities.

Read more...
DDR5 DRAM series
Vepac Electronics Computer/Embedded Technology
Innodisk has announced its DDR5 6400 DRAM series featuring the industry’s largest 64GB single-module capacity.

Read more...
Generate waveforms at 10 GS/s
Vepac Electronics Computer/Embedded Technology
New flagship arbitrary waveform generator cards from Spectrum Instrumentation generate waveforms with 2,5 GHz bandwidth and 16-bit vertical resolution.

Read more...
Quad-port 10GBASE-T controller
Rugged Interconnect Technologies Computer/Embedded Technology
he SN4-DJEMBE, available from Rugged Interconnect, is a networking adaptor card for CompactPCI Serial systems, equipped with four individual controllers for 10GBASE-T.

Read more...
HPE policy management platform
Computer/Embedded Technology
Duxbury Networking has announced the availability of the HPE Aruba ClearPass policy management platform, that enables business and personal devices to connect to an organisational level, in compliance with corporate security policies.

Read more...
IoT gateways
Brandwagon Distribution Computer/Embedded Technology
IoT Gateways are hardware and software devices that are responsible for collecting data from connected devices, managing communication between devices and the cloud, and processing and analysing the data before sending it to the cloud for further analysis.

Read more...









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.




© Technews Publishing (Pty) Ltd | All Rights Reserved