I fear I'm just overcomplicating this, but wanted to ask before I let any blue smoke out.
I am using an Arduino Uno as an interpreter in the middle of an automotive test control stand. This stand is normally driven by a piece of custom (read: Closed source, no one knows how it works anymore nor has any documentation on it...) hardware that does all the controls work. One of it's current outputs is a position command mapped to 0-5v on a 2 wire BNC. This was normally fed into an Oscilloscope to provide the baseline signal to compare another "actual position" signal to in data logging.
My goal is to take a parallel "copy" of that 0-5v signal and read it into an analog pin of my Uno, do some calcs, and control a stepper motor. I already have the stepper motor control and analogRead() coded, works great with a normal voltage divider/3 wire analog sensor concept. My problem is I have a 0-5v 2 wire signal.
My basic knowledge of Oscilloscopes tells me the two wires of the BNC connector would be connected through a large resistor and the "sense" lead tapped off the + lead (all internally in the Oscope). My assumption in using the arduino is that I need to connect the + lead to A0, and connect the + lead back to the - lead of the BNC cable via a large resistor, thus creating a voltage divider similarly to how the Oscope is setup internally. Is this making any sense? Can I somehow use an internal pullup resistor or something to achieve this? If the 0-5v signal is low enough current, would it be safe to forego the divider and just directly hook the + to A0 and the - side of the BNC cable to GND?
Thanks in advance for any guidance.