A non-iterative, polynomial, 2-dimensional calibration method implemented in a microcontroller

Output signal handling of a smart sensor usually involves a calibration facility to correct for input-output nonidealities which comprise offset, gain errors, non-linearity errors and cross-sensitivity. In this paper, a calibration method is presented which features a progressive improvement in the sensor calibrated transfer towards the desired transfer as the user proceeds from one calibration point to the next. The method is based on a set of mathematical formulas whereby a calibration coefficient can be calculated at a selected calibration point and used to calculate a first correction of the sensor transfer curve. Further improvements in the sensor transfer can be obtained by repeating the process far a second calibration point using the transfer resulting from the first calibration, without the need to review the calibration already carried out at the first point. The process can be repeated until the desired error reduction is obtained. The calibration method achieves a polynomial transfer correction. Software implementation of the method using an 8-bit microcontroller is described and simulation results for a number of examples are presented which show the performance of the method.