The disclosure is directed to a capacitive sensor for measuring a small biomedical electrical charge originating from an object under test comprising input circuit elements having an electrode for sensing the charge to provide an output signal that is a function of the charge being measured, wherein the electrode has no electrical contact with the object amplification circuit elements (A) connected to the input circuit elements processing circuit elements configured for receiving and processing the amplified output signal and to provide the measurement and conditioning and monitoring circuit elements coupled to at least the input circuit elements comprising monitoring circuit elements and conditioning circuit elements (Rl) wherein the monitoring circuit elements are configured for monitoring the amplified output signal to detect an error in a measurement that is greater than a preset value caused by charge buildup on the electrode and wherein the conditioning circuit elements are configured to be activated for. discharging the electrode when the error in the measurement is detected by the monitoring circuit elements and the conditioning circuit elements are configured to be deactivated, when the error in the measurement is no longer detected.Linvention concerne un capteur capacitif servant à mesurer une petite charge électrique biomédicale provenant dun objet testé, qui comprend des éléments de circuit dentrée comportant une électrode pour détecter la charge et qui produisent un signal de sortie en fonction de la charge mesurée, lélectrode nétant pas en contact électrique avec lobjet des éléments de circuit damplification connectés aux éléments de circuit dentrée des éléments de circuit de traitement conçus pour recevoir et traiter le signal de sortie amplifié et effectuer la mesure et des éléments de conditionnement et de surveillance couplés au moins aux éléments de circuit dentrée et qui comprennent des éléments de circuit de surveillance et des éléments de circu
