Could MagicDAQ's isolation be inside the can? (like motherboards with built-in Ethernet phy components)
Go to magic DAC website. It's Data Sheet does not specify a Hipot isolation voltage. It only states that the USB cable FG (Frame Ground) has a 1 megaohm series resistor to the MagicDAQ DGND / AGND.
See Quote 1:
The USB cable GND is not electrically connected to the MagicDAQ DGND / AGND. This ensures that measurements are not affected by the computer the MagicDAQ is connected to.
See Quote 2:
1M Ohm resistance between USB Cable GND and DGND/AGND
They do not understand the wording about USB isolation and what this supposed to mean in our field of test equipment.
Take their words at face value and you will get nailed...
All Dave has to do is continuity measure the USB GND pin, (not the usb connector GND, but the GND power out pin.) and any GND on the IO connectors. If it is anything less than 1 megaohm, then you know the USB is not isolated at all and 'Magic DAQ' might end up with some very displeased customers and potential fires or damage to your valuable PC if you take their word at face value.
I did not see true Optocouplers and proper HV clearance spacing on that PCB in Dave's video. In fact, the clearly visible 1M resistor next to the USB connector with a small parallel cap looked like an 0603. Clearly not designed to isolate any high voltage.