A sensor signal on a knob
Create a 0–2.5 V adjustable signal without a microcontroller.
Difficulty: Breadboard. Estimated build time: about 20 minutes. 4-line bill of materials. Compare supplier offers when available. A potentiometer is a movable divider.
Prepare the bench
Use an isolated, regulated 5 V source with a 20 mA current limit and a digital voltmeter with approximately 10 MΩ input resistance. These are bench tools, not included in the shopping list. Disconnect power before changing connections. Confirm breadboard rail continuity and check for supply shorts before powering up.
Identify the wiper first
With power disconnected, use resistance mode to find the two end terminals of a 10 kΩ linear potentiometer: resistance between them stays about 10 kΩ while you turn the shaft. The remaining terminal is the wiper. Do not assume a terminal order from appearance.
Limit the adjustment range
Connect +5 V through a fixed 10 kΩ resistor to one pot end. Connect the other end to ground. The pot end-to-end voltage is approximately 2.5 V. Measure wiper to ground with the meter in DC volts; turning the knob sweeps approximately 0 to 2.5 V.
Try loading the signal
Power off and add 10 kΩ from the wiper to ground. Repeat several knob positions and compare with the unloaded readings. This passive source is not regulated and its output resistance changes with position. Do not connect it to a real ADC until supply, input limits, common ground and acquisition requirements are checked.