Exponential with Offset
Exponential growth or decay toward a constant level. Use it for cooling curves, capacitor charging and discharging, and decays measured on a background.
Parameters
- Value of y − C at x = 0.
- Rate constant, in inverse units of x: positive for growth, negative for decay. For a decay, the time constant is −1/b.
- Constant offset: the level a decay approaches.
Tips
- For a decay, the half-life is ln 2/|b|. Exponential Decay (Half-life) fits the half-life directly.
- Automatic starting values come from a straight line fitted to ln y, so they need positive y and leave out C. If the fit fails, enter guesses: C near the level the data approach, A near the first y minus C, and, for a decay, b ≈ −1 divided by the time the data take to fall about two thirds of the way to C.
- If the data have no offset, enter 0 as the Guess for C and check Fix.