Mastering Internet of Things

Converting to a physical quantity

It is not sufficient for a sensor to have a numerical raw value of the measured quantity. It only tells us something if we know something more about the raw value. We must therefore convert it to a known physical unit. We must also provide an estimate of the precision (or error) the value has.

A sensor measuring a physical quantity should report a numerical value, its physical unit, and the corresponding precision, or error of the estimate.

To avoid creating a complex mathematical model that converts our measured light intensity into a known physical unit, which would go beyond the scope of this book, we convert it to a percentage value. Since we've gained a factor of five of precision using our averaging ...