Please see the UPDATE section below! The question still stands (with new info).
I don't feel the need to open a new one, but let me know if you think otherwise.
Is AmazonCommercial 600A AC/DC Clamp Meter (https://www.amazon.com/dp/B07VX41MPR/) making any sense with clamped current measurements? It shows weird values, and even weirder - it shows current when there is no wire inside the clamp.
I wanted to use it to catch parasitic draw from the automotive 12V battery, but don't know if I can trust the tool.
Kill-a-Watt is displaying AC current in all photos, ClampMeter is set to match current in the wire.
First 2 photos show original incorrect approach: clamp has to go around a single wire!
[I removed other extra photos of incorrect measurements]
As suggested, I wrapped the ClampMeter in aluminum foil, and even grounded that "cage". Ordered a second unit; one shows 1.2, the other -1.28 A DC, with no wires clamped - they don't even agree next to each other (both set with fresh batteries from the same batch):
But at least in AC mode with no wire in the clamp displayed reading is always 0.0A..
DC mode however is totally confusing. Tried to actually clamp around the vehicle's 12V battery feed. I'll spare you for now the many photos (unless asked), but the gist is: while in the air with clamp still closed, no wires inside, ~2ft away from battery it shows -1.7A. Getting closer to the battery raises the value up to -2A. Clamped over negative feed (single wire) shows -0.84A with shut off engine and no accessories.. Oh, I'll take it into the forest and get an ambient reading there!
There is a [Rel] button that should reset the measurement relative to ambient. But if I keep it depressed, while clamping and taking a reading, display will continue showing 0.0A. If the button is pressed momentarily display changes to 0.0A for that short interval, but comes back to weird (ambient?) reading as soon as the button is released.
Yes, I do have concerns about this $80 instrument's accuracy!
How to explain two units displaying very different ambient readings in the same spot at the same time? Which one to trust? How to make sense of it all?
And how [in theory?] should I read accurate DC current with clamp?