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 (R1) 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.
