Pressure signal processing

A method that receives force values corresponding to a plurality of piezoelectric sensors that correspond to a physical location on a touch panel S1. Receiving an identification of which of the force values have been influenced by being coupled to an external electric field S2. If any of the force values have been identified as being influenced by being coupled to external fields, setting the corresponding values as excluded and the remaining values as valid S5. Interpolating or extrapolating, based on the valid values, one or more reconstructed force values that correspond to the physical locations of the respective excluded values S6. The method then may output the valid and reconstructed force values S7. It then may decide to continue the method and repeat the process from the start S8. The method may use polynomial interpolation to reconstruct the valid force values. It may also use linear interpolation, or spatial gradients.