I want to measure deep sleep currents of a microcontroller (and a module) and the best way to do it seems to be the tinyCurrent, which has a convenient BNC connector for output directly to an oscilloscope (unfortunately the µCurrent Gold is not in stock anywhere). The microcontroller sometimes has a USBasp programmer attached, which is mains-grounded through the computer, and the oscilloscope is mains-grounded too.
My reading and watching has left me with the impression that it's best to avoid probing a mains-grounded DUT with a mains-grounded oscilloscope because it can create a potentially dangerous ground loop. I could detach the USBasp and use my bench power supply every time I measure sleep currents, but I would prefer to solve it with a USB isolator so that I have less replugging to do and also avoid accidentally damaging something.
The
documentation of the competing Current Ranger has a page on proper usage. Here USB isolators and ground loops are also mentioned:
But it’s not OK:
to measure a DUT that is mains/earth powered/connected, with an oscilloscope/DMM that is also mains/earth connectedAdditionally, I watched a
YouTube video comparing the µCurrent and Current Ranger, and the author also recommends using an isolator for his ESP32.
I see a huge range of prices from
6,87 € on Aliexpress to
62,10 € on Reichelt. Many of them are based on the ADUM3160. Also, the ones that I keep seeing recommended (in the video and the documentation above for example) look exactly like the cheap one on Aliexpress. Will the cheap one do or should I invest more?
Thanks for your input!