Far-seeker:
KeithRB:
That is why they have a thing called a voltage divider.That's possible of course, but precision is potentially going to take a big hit even before the resolution of the ADC is factored in. From the perspective of the signal's information content a voltage divider going from 5 to 15 V down to 0 to 5 V means there will be roughly three times less usable information detectable in the output signal. For some applications that's not a problem, for others it will be. Instead, I would check to see if there is an affordable ADC chip/module that can handle the orignal input voltage and output serial communication of some sort at 5 VDC.
I suspect you will have a very hard time trying to find, if any indeed exist, any ADC chips that allow input signal voltages to be higher then it's Vcc voltage (or lower then Vdd), which in most cases I'm aware of is limited to standard Vcc values of 5 vdc or lower. And any ADC type module that can handle that high of input voltages would just be using some kind of programmable front end attenuator (voltage divider) and still process the ADC conversion at standard Vcc values.
Lefty