Micro-magnetic　testing　technology　is　capable　of　non-destructively　evaluating　the　mechanical　properties　and　residual　stress　in　ferromagnetic　components.　In　the　applications　of　micro-magnetic　testing　technology,　several　types　of　magnetic　signals,　such　as　magnetic　Barkhausen　noise,　incremental　permeability,　tangential　magnetic　field　and　eddy　current,　etc.　are　used　to　characterize　the　target　properties　(mechanical　properties　and　residual　stress).　In　this　paper,　a　unique　framework　for　multifunctional　micro-magnetic　sensor　design　is　proposed.　Accordingly,　a　multifunctional　micro-magnetic　instrument　is　developed.　Intermittently　superimposed　magnetic　fields　of　high　(several　kHz)　and　low　frequencies　(several　Hz)　are　used　for　material　magnetization.　Combined　magnetic　sensors　are　employed　to　measure　a　total　of　five　types　of　signals,　including　the　magnetic　Barkhausen　noise,　incremental　permeability,　eddy　currents,　tangential　magnetic　field　and　main　flux.　Especially,　twisted-pair　wiring　was　used　for　winding　two　identical　sensing　coils.　One　of　the　sensing　coils　is　used　for　eddy　current　or　incremental　permeability　detection　and　the　rest　one　acts　as　a　compensatory　coil　to　suppress　the　strong　mutual　induction　voltage　in　detection　coil.　The　entire　instrument　is　composed　of　a　multi-channel　signal　generator,　a　power　amplifier,　signal　processing　circuits　embedded　into　the　multifunctional　sensor　and　a　four-channel　signal　acquisition　device.　The　multi-channel　signal　generator　is　constructed　based　on　FPGA　and　high　speed　D/A　converters.　The　direct　digital　synthesizer　and　state　machine　are　programed　in　FPGA　to　enable　the　excitation　of　intermittently　superimposed　signals　of　high　and　low　frequencies.　Carefully　experiments　were　performed　to　test　the　performances　of　the　developed　instrument.　The　results　obtained　from　different　types　of　steels　proved　that　the　developed　instrument　can　acquire　five　types　of　magnetic　signals　with　high　SNR.　The　features　of　the　five　types　of　magnetic　signals　can　used　to　distinguish　the　material　and　its　mechanical　properties　such　as　surface　hardness.　©　Published　under　licence　by　IOP　Publishing　Ltd.