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EEVblog 1391 - Mailbag

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More mailbag!

00:00 - Panasonic S-VHS DP200 camcorder
08:23 - Home lab: Andrew Tayman
12:25 - Casio G-SHOCK Mudmaster watch teardown
24:44 - Modul Bus LCR substitution box and RT100 valve prototyping breadboard!0,746296692357891,RLC-Box2!0,746296692357891,KITRT100
KainkaLabs Youtube channel:
32:16 - eDesign Miniware MHP30 Mini BGA pre-heater
40:16 - The Snapistor!
46:53 - EPM3081 landscape format $10 pocket multimeter
50:12 - Ceramic hybrid mystery PCB
53:50 - MagicDAQ data aquisition system suitable for production testing

I don't use Odysee, so what was the magic thing Dave supposedly said?

Cliff Matthews:
Could MagicDAQ's isolation be inside the can? (like motherboards with built-in Ethernet phy components)


--- Quote from: Cliff Matthews on May 10, 2021, 12:25:39 am ---Could MagicDAQ's isolation be inside the can? (like motherboards with built-in Ethernet phy components)

--- End quote ---

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:

--- Quote ---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.
--- End quote ---

See Quote 2:

--- Quote ---1M Ohm resistance between USB Cable GND and DGND/AGND
--- End quote ---

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.

Wouldn't this do?

1500v usb isolation.


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