1.7 Temperature Tolerance

Typical tuning fork crystals are usually cut to center the nominal frequency at 25°C. Above and below 25°C, the frequency will decrease with a parabolic characteristic, as shown in Figure 1-7. The frequency shift is given by Equation 1-5, where f₀ is the target frequency at T₀ (typically 32.768 kHz at 25°C) and B is the temperature coefficient given by the crystal data sheet (typically a negative number).

$f=f_0(1+B{(T-T_0)}^2)$