Would it then make more sense to utilize two separate arduous
i still seem to get rather large jumps in the serial output associated with the led turning on or off. This occurs only for the few ms surrounding the led turning on or off.
That is probably a hardware problem, most likely caused by bad layout. The current path for the LED, that is pin -> LED -> resistor -> ground looks like it is causing some sort of ground bounce. ( you have got a resistor in line haven't you if not that is what is causing the problem ) This ground bounce is when the current path for LED and the voltage you are trying to measure is the same piece of wire. The current through the wire causes a temporary voltage drop to occur and gets added to the voltage you are trying to measure.
What is the nature of this analogue input? Is it high impedance? Is it changing rapidly?
Learning new things every day!
Me too, and I have been at it over 40 years.