The purpose of this paper is to show that the charge induced by radiation in a dielectric on which a sigma–delta control of dielectric charge is implemented, can be seen as a disturbance in a sliding mode controller. Preliminary experimental results are presented in which a MEMS device is irradiated with X-rays, while the dielectric charge control is continuously being monitored. The charge induced by radiation generates a change in the control bitstream, which is associated with the presence of an external disturbance on the governing control equations.