One day I came across a device called “Ethernet Network Isolator” and started to wonder why we would need such device as standard Ethernet system that uses twisted pair cable and RJ-45 connectors is already isolated from both ends of the cable (isolation transformers that can withstand 1500V). When the network connections made with unshielded twisted pair cables, those transformers provide galvanic isolation. The only cases that come to mind where twisted pair Ethernet can form ground loop problems are when shielded cables are used (shield can connect two end device grounds together) and some improperly implemented PoE systems (PoE should have the power isolated at same level as data but unfortunately not all product follow this standard requirement). When you stick with unshielded cables, you don’t typically hit any ground loop issues with Ethernet. If the standard isolation level is not enough, then switching to fiber optic will help – or maybe Ethernet isolator.
After some research on some product information pages and Wikipedia Network Isolator page I found out that there are some special cases where there are sensible reasons to use such extra isolation device on Ethernet network. After some more searching, I also found products designed for industrial applications and audio applications.
PATIENT PROTECTION
Galvanic isolation of the Ethernet interfaces on medical electrical equipment or systems
for which patients must be protected from harmful leakage currents in line with standards.
APPLIANCE PROTECTION
Protection of particularly valuable devices from ripple voltages and surges from the edge of the network.
MEASUREMENT TECHNOLOGY
Protection of electrical measurement and monitoring equipment from external voltages and interference voltages from the
Ethernet cabling.
POTENTIAL DIFFERENCES (BUILDING TECHNOLOGY)
Potential equalisation currents are prevented in computer systems connected via an Ethernet
cabling over greater distances.
AUDIO
Reduction of low-frequency AC voltages (mains ripples), which are caused by the network connection, to an imperceptible level.
Medical applications
Network isolators are used in the medical industry to protect patients against leakage currents. IEC standard IEC 60601-1 (3rd edition) specifically deals with medical electronic and electrical equipment and systems, and classifies non-medical devices as potential hazard sources. Network isolators work to remove this hazard, by electrically disconnecting medical devices from a network. They are often installed in the medical field in conjunction with isolation transformers, which serve to protect the patient from electrical faults. The international standard IEC 60601-1 Medical Electrical Equipment (3rd edition) specifies stringent criteria on the safety and isolation of medical devices. Very many medical institutions use Ethernet isolators for electrical safety and to keep equipment interference free. Medical-grade Ethernet isolators must follow strict regulations concerning the isolation level that an Ethernet isolator provides. Isolators marketed to meet European Medical Device Directive (EN6060-1) typically have isolation level of 4kV or higher.
Industrial applications
Network isolators have industrial applications in overcoming the problems of differing ground potentials across networks, or between network components for example to stop shield currents on shielded Ethernet cable (ground loop currents) and on electrical testing facilities where higher that normal office environment electrical disturbances are present. There are also uses in electronics testing systems where dangerous voltages are present.
Ethernet Isolator combines intrinsically safe energy limitation and galvanic isolation page tells that the FieldConnex® Ethernet Isolator combines intrinsically safe energy limitation and galvanic isolation into one product. Now Ethernet connections are plug and play in Ex-Zone 1. Intrinsically safe Ethernet Isolator EI-0D2-10Y-10B product provides galvanic isolation according to EN50020 for 10 BASE-T/100 BASE-TX. It contains active electronics and needs a power source to operate.
Audio applications
Ground loops and high frequency noise have known to cause all kinds of issues with sensitive audio systems. Especially people tuning their HiFi systems are interested could Ethernet connection be improved in some way. Because almost all the audiophiles would have experienced of tuning their own audio system with variety of cables or accessories in order to enhance the music sound from their treasured audio systems, some special HiFi equipment manufacturers have seen market for expensive Ethernet isolators for HiFi applications. So called ‘audiophile’ grade ethernet cables have made inroads into specialist audio dealers.
Audio Stream Ethernet Accessories and Cables page has information on several special (expensive) accessories that are claimed to provide improvement when used with HiFi equipment. In Ethernet isolation sector the page lists SOtM iSO-CAT6 Ethernet isolator. SOtM iSO-CAT6 Ethernet isolator product page claims that noise interference created by LAN port has enormous effect to system sound and SOtM iSO-CAT6 may offer certain varying sound improvement (for other views check reviews at 6moons and avrev). SOtM iSO-CAT6 manual says that this product provides isolation 1500Vrms, 0.5mA, 60sec (same level as normal Ethernet cards).
Are the isolators really needed in audio system? Maybe not in most cases (but there can be some special cases where extra isolation can have some effect). By default the ethernet ports are isolated with transformers. However – ground loops from shielding still can exist if you use shielded cables. If you are worried on ground loops on audio system, I recommend to use unshielded Ethernet cables, so you get no ground loop. If you are really paranoid on isolation, isolate the audio with a fiber optic cable. Some people who have written on their experiences have found out no difference on copper, isolated copper or fiber on sound quality. This no difference will also apply to special Ethernet cables: The use of solid core verses stranded or gold verses silver for the conductors for this link in particular is just putting lipstick on a pig. Again, this is digital side… The likelihood of there being a genuine difference rather than a psychoacoustic cause for the described difference is much, much lower given known physics.
How Ethernet Isolators Work
An Ethernet isolator separates the electrical currents of multiple devices: it allows the Ethernet data signals to pass without allowing the two circuits to physically contact each other. The Ethernet isolator is basically just several 1:1 Ethernet transformers put between the RJ-45 connections (two needed for 10/100 Mbit/s Ethernet, four needed for 1 Gbit/s Ethernet). Typically all those transformers are built into one transformer module similar to ones used in Ethernet cards and switches. Such isolator consists of a small PCB at the back panel with two RJ45 connectors and a LAN transformer in between. This would provide an additional 1500V to 4000V of isolation depending on the transformer chosen.
Network isolators are commercially available in various designs. Medical-grade Ethernet isolators must follow much stricter regulations concerning the isolation level that Ethernet isolators for industrial uses.
Ethernet isolators are typically constructed using the same technique as normal Ethernet port. Ethernet specification needs magnetic transformer coupling between RJ45 connector and electronics. Most modern Ethernet ports with MDIX functionality (auto-detect direct or cross-connect) use 1:1 transformers optimized for Ethernet frequencies (frequency range depends on line speed) and impedance (100 ohms) for all used signal pairs.
Transformers offer a very good common mode rejection: A transformer only “sees” the voltage accross its windings, not the common voltage both ends of the winding are driven to simultaneously. You get a differential front end without a deliberate circuit, just basic physics.
An Ethernet isolator could be basically built using one such transformer module (contains 2 or 4 transformers in one case) that is just wired between two RJ45 connectors. Standard Ethernet transformers provide typically 1500Vrms isolation. If higher isolation level is needed, a suitable special transformer with improved isolation specification needs to be manufactured. For example medical isolator can isolate the data AND the shield up to 5.000V. The nic transformers only isolate the data up to 1.500V. Here is picture of MI 1005 E Medical Built In Isolator showing that there is just transformers (inside black box in the center) and two RJ45 connectors.
Isolation is a very good idea on communications systems that are linking lots of different hardware over a wide area: You don’t want fault current/voltages in the mains wiring or devices to spread onto your communications wiring.
Ethernet transformer links:
http://www.haloelectronics.com/products/lan/ethernet/
http://www.mouser.fi/new/molex/molexRJ45jacks/
http://www.mouser.fi/new/halo-electronics/halo-ethernet-transformers/
https://www.eeweb.com/company-blog/microchip/migrating-from-the-lan9115-to-the-lan9210/
Links to more information:
http://www.diyaudio.com/forums/pc-based/154048-ethernet-galvanic-isolation.html
http://www.bb-elec.com/Learning-Center/All-White-Papers/Ethernet/Power-over-Ethernet-PoE.aspx
http://hackaday.com/2010/10/26/ethernet-connection-using-capacitive-coupling/
http://www.youritronics.com/magnetic-less-ethernet/
Some product links:
I have found those with Google search. I have not used any of those or recommend them.
http://industrialcomponent.com/baaske/2006633.html
http://industrialcomponent.com/baaske/ethernet-isolation.html
Ethernet Data Isolator – 10BASE-T/100BASE-TX
http://industrialcomponent.com/baaske/2006633.html
L-com 10/100/1000 Ethernet Data Isolator (EN60601-1 Compliant) provides isolation up to 4 kV
Bourns 360 V dc 3kA 1500 Isolated Ethernet Protector, Wall Mount Mounting is an Ethernet surge protector product that also promises to provide 5 kV isolation for 10/100/1000 Mbit/s Ethernet.
EMO EN-100C :: Network isolator for PCB mounting is intended for integration on the PCB of the device being protected. The devices in the EN-100-series meet the requirements of IEC 60601-1 (3rd edition) and IEC 60601-1-2 for medical settings
Phoenix Contact Network isolator – FL ISOLATOR 100-RJ/RJ – 2313931 is a passive passive network isolator for electrical isolation in Ethernet networks up to 4 kV and speeds of up to 100 Mbps.
https://www.mtl-inst.com/images/uploads/datasheets/is_ethernet/9468-ET.pdf
http://www.mmcchina.com/Upload/whitepaper/MMC_Whitepaper12EN.pdf
http://industrialcomponent.com/baaske/ethernet-isolation.html
http://industrialcomponent.com/baaske/2006633.html
http://www.baaske-medical.de/media/content/Datasheet_MI1005_MI1005E.pdf
http://industrialcomponent.com/baaske/2006633.html
https://www.dustinhome.fi/product/5011222413/rj45-network-isolator-6kv
https://www.dxengineering.com/parts/dxe-iso-plus-2
https://www.phoenixcontact.com/en-pc/products/network-isolator-fl-isolator-1000-rj-rj-2313915
Sources:
http://www.tech-faq.com/ethernet-isolator.html
http://electronics.stackexchange.com/questions/180415/ethernet-3000v-isolation
http://www.mouser.fi/new/halo-electronics/halo-ethernet-transformers/
http://www.diyaudio.com/forums/pc-based/154048-ethernet-galvanic-isolation.html
http://www.6moons.com/audioreviews2/sotm2/1.html
http://www.avrev.com/home-theater-accessories/acoustics-eq-room-tuning/sotm-iso-cat6-lan-filter-and-tx-usbhub-review-3.html
http://www.computeraudiophile.com/f22-networking-networked-audio-and-streaming/audiophile-ethernet-cables-13798/
http://www.computeraudiophile.com/f22-networking-networked-audio-and-streaming/ethernet-cables-audiostream-test-17713/
http://electronics.stackexchange.com/questions/27756/why-are-ethernet-rj45-sockets-magnetically-coupled/27762
http://www.diyaudio.com/forums/pc-based/154048-ethernet-galvanic-isolation.html
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