Different measurement between PPK2 Ampere meter and Source meter mode

[Md Mazedul Islam Khan]

I have already seen some topics about this, but still struggling to understand the correct measurement and difference between the PPK2 Ampere meter and Source meter mode. I used nRF 52840_DK with Thread: CoAP Server to measure the power using PPK2 in both modes, and I saw different numbers. The differences aren't even close to each other, and that's where I am struggling.

Source meter mode

Ampeter meter mode

As you can see, the average number of 26.24 nA for the Ampeter meter mode and 9.73 mA for the Source meter mode.

Why the huge difference? What am I missing?

Note: I am powering both of the devices through USB.

[Achim Kraus]

> I am powering both of the devices through USB.

That makes only sense with the "Amper meter mode", with the "Source meter", the device will have two sources. For that "Source meter" mode, please disconnect the device from USB.

[Md Mazedul Islam Khan]

Yes, in source meter mode, I never connect the device through USB as power comes from PPK itself

[Achim Kraus]

Then I misunderstood "I am powering both of the devices through USB.".

I guess, that there is a second "power path" for the "Amper meter" case. At least, using a nRF9160-DK or a nRF9160-Feather I never recognized a that large difference in measured values using the "Meter" or "Source" mode, both worked fine and the values are quite the same.

[Md Mazedul Islam Khan]

I kept the 'Enable power mode' turned on for both Ampere mode and Source meter mode. When I disabled the option 'Enable power mode' in Ampere meter mode, I see a different average number, which is 8.58 pA. But that's still a huge difference from Source meter mode where the number was 9.73 mA

[Achim Kraus]

> I kept the 'Enable power mode' turned on for both Ampere mode and Source meter mode.

That's well, otherwise it would not work.

> When I disabled the option 'Enable power mode' in Ampere meter mode

Does your target device run with that setting? If so, you have that second "power path".

Again, I use the PPK II a lot, I haven't observed a significant difference between source and meter mode. With that, I guess you have just a failure in your setup, e.g. a second "power path".

[Achim Kraus]

My UI shows "Enable power output", I guess, that's what you refer to.