Raspberry Pi 3 Cookbook for Python Programmers - Third Edition

Scaling and calibrating data

You may have noticed that it can sometimes be difficult to interpret data read from an ADC, since the value is just a number. A number isn't much help on its own; all it can tell you is that the environment is slightly hotter or slightly darker than the previous sample. However, if you can use another device to provide comparable values (such as the current room temperature), you can then calibrate your sensor data to provide more useful real-world information.

To obtain a rough calibration, we shall use two samples to create a linear fit model that can then be used to estimate real-world values for other ADC readings (this assumes the sensor itself is mostly linear in its response). The following diagram shows ...