I've been following this flex-sensor-arduino tutorial on setting up a simple flex sensor with Arduino, and I got confused on this part:
The flex sensor changes its resistance when flexed so we can measure that change using one of the Arduino’s analog pins. But to do that we need a fixed resistor (not changing) that we can use for that comparison (We are using a 22K resistor). This is called a voltage divider and divides the 5v between the flex sensor and the resistor.
Why exactly did I need to add the second resistor? Couldn't the Arduino just get the voltage change from a single variable resistor that is the flex sensor? I'm very new to electronics, so an explanation in simple terms would be great.