Carbon　steel　has　proven　to　be　an　important　structural　and　functional　material　that　plays　an　irreplaceable　role　in　the　worldwide　economy.　The　influence　of　carbon　on　the　mechanical　and　magnetic　properties　of　the　steel　is　well　understood.　Thus,　the　precise　knowledge　of　the　amount　of　carbon　content　in　steel　is　crucial.　Magnetic　Barkhausen　noise　(MBN),　magnetic　hysteresis　loop　(MHL),　and　impedance　measurements　are　reliable　tools　to　assess　carbon　content.　In　this　work,　a　multifunctional　induction　coil　sensor　used　for　MBN,　MHL,　and　impedance　measurements　is　designed　and　optimized.　A　multifunctional　measurement　system　using　the　optimized　induction　coil　is　employed　to　measure　MBN,　MHL,　and　impedance　signals.　The　parabolic　dependence　of　the　maximum　value　of　MBN　envelope　on　carbon　content　in　steel　is　theoretically　analyzed　and　experimentally　verified.　Coercive　field　and　remanence　from　MHL　measurements　as　well　as　the　maximum　impedance　value　are　found　to　be　proportional　to　carbon　content　and　their　dependence　is　explained　with　analytical　simulations.　　©　1965-2012　IEEE.