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Old July 30th, 2020, 08:27 AM   #1
Gadelric
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EMF Shielding

Team,

I've got an older piece of equipment that is using serial and usb connections.
We have started to get garbage data, and I am starting to lean on EMF issues.
Do you guys have any recommendations as to where I should get some shielded serial and usb cables from?
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Old July 30th, 2020, 07:56 PM   #2
Bit_Bucket_07
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Quote:
Originally Posted by Gadelric View Post
Team,

I've got an older piece of equipment that is using serial and usb connections.
We have started to get garbage data, and I am starting to lean on EMF issues.
Do you guys have any recommendations as to where I should get some shielded serial and usb cables from?
It's been my experience that shields will only get you so far in relieving EMF issues. Steel conduit will usually stop it though. If it passes through an enclosure, then you can use sealtite to get from conduit to conduit inside the panel.
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Old July 31st, 2020, 06:25 AM   #3
drforsythe
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I agree with Bit_Bucket_07's advice. Shielding works to some extent, but not perfect, especially if you cannot ground one end (and only one end) of the shield. Metallic conduit / greenfield/ seal-tite is more effective, but not all serial and USB connections leave the enclosure. I have had good luck reducing the effects of noise by using split ferrite cores that can be snapped onto cables with connectors. Good luck.
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Old July 31st, 2020, 07:20 AM   #4
JesperMP
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For serial, do you mean RS232 or RS422/RS485 ?
If RS232, definitely consider changing over to RS422 or RS485. More important than shielding, even though shielding is important.
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Old July 31st, 2020, 10:51 AM   #5
Gadelric
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Thank you guys for the advice.
The cabling is all contained within the panel.
I have some clamp on ferrite cores coming in, and will try them.
I only need to keep this thing running for about a year and then it goes to the barn.
Although I hate the idea of just pulling the cables out of the wire tray and zipping them up, but in the end if that is what corrects the noise issue, that's what we will do.

When I researched ferrite cores and proper implementation, it was stated that there are 2 ways to install the cores, Hi-speed = single pass through, low speed requires a double pass through the core.

This is CAN communication, would anyone know if this is hi or low speed coms?
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Old July 31st, 2020, 10:08 PM   #6
AlfredoQuintero
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Depending on the CAN flavour, this network supports up to 1 Mbaud. By the way, CAN requires two 120 OHM terminator resistors between the CAN_L and CAN_H signals.
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