Overloading and noise question

[noch]

Hello, I am just trying to better understand a couple of things about the CR.

My setup is, the CR powered by its own lipo and my DUT (various dev boards) powered by a separate lipo. 

If I am measuring current on a board that is consuming 40mA and switch the CR to the uA range will that damage it eventually? 
I did this a couple of times already and the OLED says "Overloaded" or similar.  I read in the guide the ranges are 3300ma/ua/na but I also read in a post that overloading the amps should not damage them.  Its not something I plan on doing for any reason other than by accident.

I noticed when I am testing one of my esp32 style boards the OLED values in the ua range jump fairly significantly (8ua-100ua).  I have read how the OLED values are just there for a quick ballpark but since it was ranging so much I just wanted to ask.  My output readings with a DMM are steady and as expected.  My readings with a scope reflect what the OLED shows.  Based on what I have read I assume this is just noise.  I guess because a DMM reads so much slower it just does not reflect that and gives a more steady reading?

Thanks

[Felix]

When you overload a range, it means the opamps are overloaded, driven to rails. That is not a condition you want to do often. The more overloaded the more undesirable this is. Yes it can possibly eventually damage the opamps, less so the shunts.

The CR only reads the ADC and does averaging in the SAMD ADC hardware. The DMM does RMS which is why it will be more accurate but probably slower responding to peaks.
While the OLED is being written to and the ADC is sampling there will be some coupled noise into the raw reading.
If you want the lowest noise turn OFF autoranging and range manually, and also unplug the OLED and use the scope/DMM instead of the OLED.