IEVref: 103-05-26 ID: Language: en Status: Standard Term: time constant Synonym1: Synonym2: Synonym3: Symbol: τ Definition: time τ in the expression $F\left(t\right)=A+B{\mathrm{e}}^{-t/\tau }$ of a quantity F growing or decaying exponentially towards a constant value A with increasing time t, or in the expression $F\left(t\right)=A+f\left(t\right){\mathrm{e}}^{-t/\tau }$ of an exponentially damped oscillation, where f is a periodic function of timeNote 1 to entry: The time constant of an exponentially varying quantity is the duration of a time interval at the end of which the absolute value of the difference between the quantity and the limit has decreased to 1/e of the absolute value of this difference at the beginning of the time interval, where e is the base of natural logarithms. Note 2 to entry: The time constant of a damped oscillation is the inverse of the damping coefficient. Publication date: 2009-12 Source: Replaces: Internal notes: 2017-02-20: Editorial revisions in accordance with the information provided in C00020 (IEV 103) - evaluation. JGO CO remarks: TC/SC remarks: VT remarks: Domain1: Domain2: Domain3: Domain4: Domain5: