Hello,
A quick and easy question.
Are Salae probes differential probes?
I mean, are the 8 or 16 GND pins independent or are they connected together?
Thank you.
The inputs are single ended and share a common ground which is also the USB ground and thus the host computer’s ground!
Be very careful that the ground for the DUT can be safeley connected to the computer ground without causing issues with the DUT or excessive ground current through the Saleae Logic device to the host computer ground!
Indeed! This is the same as oscilloscopes. Sometimes people get to thinking that because their multimeter is isolated that means everything is. NO! The Saleae Logic and almost all oscilloscopes with their passive probes are not isolated from the circuit. All grounds are technically shared. That doesn’t necessarily mean you shouldn’t still connect to grounds as close to your pins under test as you can. More grounding is better. But, all grounds must be at the same potential or you will create a short circuit that you won’t like.
However, it should be said that you can still get some isolation if you use a laptop. Plug the Logic into the laptop and DO NOT PLUG THE LAPTOP INTO AC POWER. Now, it’s all floating. The laptop, the Logic, and your DUT are all sharing a ground. But, this ground could be considered floating, at least insomuch as the laptop and Logic are now floating at the same ground potential as the DUT. If it is also floating then you have a fully isolated system. If it is grounded via some means then at least you have only one ground point which is for the best.
Bottom line, unless you have a good reason not to, I’d recommend using a portable logic analyzer floating with a laptop that is not plugged in.
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Unless the DUT is “floating” at 500V!