What effect does changing ADC0 Reference have on ADC measurement resolution?

[RRdae]

I have a few questions about the ADC reference voltage as it pertains to use on the K66 (Teensy 3.6). Specifically, I am trying to read the amplified output of a 50 amp current sense resistor and would like to increase low end resolution without sacrificing the range.

1. Does changing the reference voltage to 1.2v from 3.3v increase the resolution of the ADC measurement at the expense of the measurement range (16bit over 0-1.2v vs 0-3v)?

2. If 1 is correct, can the reference voltage be selectively changed by the main program to provide two different levels of resolution depending on the current ADC reading?
For example (ADC @ 16bit):
Range 1: 65536 steps from 0 to 1.2v
Range 2: 41705 steps from 1.2 to 3.3v

3. Is it as simple as changing REFSEL on ADCx_SC2, or does the associated ADC need to be disabled/enabled when the Reference is changed?

4. If the reference is set at 1.2v and a stray signal is encountered >1.2v (but less than 3.3v) before the reference has changed, could the Teensy be damaged?

Thank you

 

[defragster]

Without testing or looking expectations ::

Not sure but seems that after ref change it could require the recalibration step to be accurate, that would entail some delay in the reading.

On T_3.2 and T_3.5 that can tolerate up to 5V on input - anything 3.3V or above is seen as MAX value. Given the T_3.6 is designed for 3.3V - with 1.2V Ref it would seem anything over that would likewise be MAX value without harm.

For a given resolution it should scale full value up to the Ref voltage in use.

IIRC ... prior notes suggest 13 bit stable resolution at best with really clean setup.