  The Arduino platform is widely used in education of physics to perform a
number of different measurements. Teachers and students can build their own
instruments using various sensors, the analogue-to-digital converter of the
Arduino board and code to calculate and display the result. In several cases
this can mean incautious reproduction of what can be found on the Internet and
an in-depth understanding can be missing. Here we thoroughly analyse a
frequently used resistance measurement method and show demonstration
experiments as well to make it clear.
