Editing Relative permittivity (section)

=== Environment ===
The relative permittivity of air changes with temperature, humidity, and barometric pressure.<ref>5×10<sup>−6</sup>/°C, 1.4×10<sup>−6</sup>/%RH and 100×10<sup>−6</sup>/atm respectively. See [http://repository.tudelft.nl/islandora/object/uuid:e2234250-950d-4eb5-9f2e-b5b8e67af2e5/datastream/OBJ/download A Low Cost Integrated Interface for Capacitive Sensors], Ali Heidary, 2010, Thesis, p. 12. {{ISBN|9789461130136}}.</ref> Sensors can be constructed to detect changes in capacitance caused by changes in the relative permittivity. Most of this change is due to effects of temperature and humidity as the barometric pressure is fairly stable. Using the capacitance change, along with the measured temperature, the relative humidity can be obtained using engineering formulas.