USB isolation from mani earth for bench scoping?

[Chriss]

Hi!
I'm not sure does I'm in the right section of this forum, but hope yes.

I always worry about when I connect my scope to mine development board for AVR which is connected/powered from my desktop PC USB port.

My scope is a Siglent SDS1052DL+ scope, the PC usb GND is connected to mains GND earth, together with my scope of course.

somehow I always have some strange feeling when I try to connect my scope probe to the dev board to check for signals.

Is there any/cheap way to make the usb port complete isolated from the dev board but still to use it for powering and programming the board?

For now I never experienced any problem but I'm afraid, one day sht will happen... 

Thank you.

[Cosmic Osmo]

It probably isn't really an issue, because the scope ground and the PC's ground are probably both tied to mains earth. That said, an overabundance of caution can't be a bad thing.

USB wall warts are generally isolated, so use one of those to power your project while probing, or a USB battery bank.

For programming, either get a USB isolator ($30 from Adafruit or wherever) or just don't probe while programming.

[coromonadalix]

you have many usb isolators on Ebay under 20$ usd    1.5 k and 3 kv isolation depending on the choosen models

I had no problems with them

[Chriss]

Assume something like this will do the job:
https://www.ebay.com/itm/USB-1500v-Isolator-Isolator-ADUM4160-USB-To-USB-ADUM4160-ADUM3160-Module/263558200420?hash=item3d5d4afc64:g:VVYAAOSwmMNcRWGS

[0culus]

It probably isn't really an issue, because the scope ground and the PC's ground are probably both tied to mains earth. That said, an overabundance of caution can't be a bad thing.

USB wall warts are generally isolated, so use one of those to power your project while probing, or a USB battery bank.

For programming, either get a USB isolator ($30 from Adafruit or wherever) or just don't probe while programming.

I probe circuits connected to USB a lot (FPGA boards mostly), both with o-scope and logic analyzer with no issues. HOWEVER, if you want to take precautions, I'd recommend instead powering your DUT with a quality DC supply that has floating outputs and solid current limiting. If you short something out, a battery bank will probably happily deliver a ton of current.

[Chriss]

Ok, I bought one of these USB isolator from the link above.
I will report here when it arrive.

I hope this little gadget will give me more peace while scoping... 

[Zucca]

I bought it too... since in my german apartment the PE is just the N wire.
Unfortunately it is just not a high speed but only 12Mbps.

[Chriss]

12Mbps should also do the r/w of the uC but it will isolate the gnd prom the pc... I hope ao. :-)

Sent from my SM-J500F using Tapatalk

[David Hess]

I would worry also.

USB isolators are available which also supply isolated power.

[coromonadalix]

If you want a true isolation, use an isolation transformer on the main equipment you need to be connected with

An ADUM4160  normaly is safe for most app,  sure you dont always get the full usb speed

some claiming a full isolated speed  up to 100$ usd ??

https://www.mouser.com/datasheet/2/214/kxusb150ds-179743.pdf
https://www.mouser.ca/new/keterex/keterex-usb-150-isolator/
https://hifimediy.com/high-speed-usb-isolator-480Mbps
https://www.virtins.com/USB2ISO.shtml