A computer implemented method of calibrating a device comprising the steps of: deriving an analytic expression for a variable to be optimised of the device in terms of at least one parameter of the device, transforming the analytic expression into polynomial form of the at least one parameter of the device, the polynomial form comprising N coefficients, capturing at least N samples of a value of the variable from the device under calibration, each sample being a result of a different independent pre-determined value of the at least one parameter, applying the captured variable values and the corresponding at least one parameter values to the polynomial form, obtaining optimal values of the at least one parameter from the applying step to calibrate the device.