Method for operating a metal detector that comprises a balanced coil system with a drive coil that is connected to a transmitter unit , which provides a transmitter signal (s1) with at least one operating frequency (f TX ), and with a first and a second detection coil that provide an output signal (s2) to a receiver unit , that processes a related receiver signal (s3), which comprises an imbalance signal and other signals relating to products and/or metal contaminants, and that provides demodulated digital in-phase and quadrature components (d I , d Q ) which are analysed in a control unit in order to detect metal contaminants in products that are examined by the metal detector, characterized by the steps of □ using at least one low pass filter (40I; 40Q) for separating the demodulated digital in-phase and quadrature components (d I , d Q ) of the imbalance signal in a signal controller from the demodulated digital in-phase and quadrature components (d I , d Q ) of the related receiver signal (s3); □ processing the digital in-phase and digital quadrature components (d I , d Q ) of the imbalance signal in a signal controller for separating the imbalance signal from signals relating to products and contaminants and providing control data to a compensation unit that is used for compensating the imbalance signal, wherein said step of processing comprises: applying the digital in-phase components (d I ) of the imbalance signal to a first control unit , which provides an in-phase control component (d CI ) for the imbalance signal and applying the digital quadrature components (d Q ) of the imbalance signal to a second control unit , which provides a quadrature control component (d CQ ) for the imbalance signal; □ in the compensation unit , synthesizing a digital compensation signal (d COMP ) with the frequency of the imbalance signal, which corresponds to the at least one operating frequency (f TX ), and with a phase and magnitude according to the in-phase and quadrature control components (d CI , d CQ ) provided for the imbalance signal; □ converting the digital compensation signal (d COMP ) into an analogue compensation signal (a COMP ), and □ applying the analogue compensation signal (a COMP ) to the balanced coil system or to the receiver signal (s2, s3) for compensating the imbalance signal. □ using at least one low pass filter (40I; 40Q) for separating the demodulated digital in-phase and quadrature components (d I , d Q ) of the imbalance signal in a signal controller from the demodulated digital in-phase and quadrature components (d I , d Q ) of the related receiver signal (s3); □ processing the digital in-phase and digital quadrature components (d I , d Q ) of the imbalance signal in a signal controller for separating the imbalance signal from signals relating to products and contaminants and providing control data to a compensation unit that is used for compensating the imbalance signal, wherein said step of processing comprises: applying the digital in-phase components (d I ) of the imbalance signal to a first control unit , which provides an in-phase control component (d CI ) for the imbalance signal and applying the digital quadrature components (d Q ) of the imbalance signal to a second control unit , which provides a quadrature control component (d CQ ) for the imbalance signal; □ in the compensation unit , synthesizing a digital compensation signal (d COMP ) with the frequency of the imbalance signal, which corresponds to the at least one operating frequency (f TX ), and with a phase and magnitude according to the in-phase and quadrature control components (d CI , d CQ ) provided for the imbalance signal; □ converting the digital compensation signal (d COMP ) into an analogue compensation signal (a COMP ), and □ applying the analogue compensation signal (a COMP ) to the balanced coil system or to the receiver signal (s2, s3) for compensating the imbalance signal. <EOS>