Editing Crystal oscillator (section)

===Temperature effects===
A crystal's frequency characteristic depends on the shape or "cut" of the crystal. A tuning-fork crystal is usually cut such that its frequency dependence on temperature is quadratic with the maximum around 25&nbsp;°C.{{Citation needed|date=November 2016}} This means that a tuning-fork crystal oscillator resonates close to its target frequency at room temperature, but slows when the temperature either increases or decreases from room temperature. A common parabolic coefficient for a 32&nbsp;kHz tuning-fork crystal is −0.04 ppm/°C<sup>2</sup>:{{Citation needed|date=November 2016}}

: <math>f = f_0\left[1 - 0.04~\text{ppm}/^\circ\text{C}^2 \cdot (T - T_0)^2\right].</math>

In a real application, this means that a clock built using a regular 32&nbsp;kHz tuning-fork crystal keeps good time at room temperature, but loses 2 minutes per year at 10&nbsp;°C above or below room temperature and loses 8 minutes per year at 20&nbsp;°C above or below room temperature due to the quartz crystal.