Analog circuits component diagnosis is a challenging task requiring expensive resources. This paper presents a low cost method to identify deviations in multiple component values using a precharacterisation of the impact of the deviations on the digital signatures for a set of input excitations. The method predicts several circuit under diagnosis (CUD) deviations by mapping them to a scalar value that indicates the discrepancy of the defective and golden digital signatures. Input excitation consists of a small set of sinusoidal signals with different frequencies. A digital signature is generated for every excitation set and compared to the golden response. The scalar discrepancy values are used to obtain the component deviations of the CUD. In order to generate the signatures, a CMOS monitor circuit has been designed and fabricated. The method is applied to the identification of capacitance deviations in a Biquad filter. Simulated results show the possibilities of the proposal