An integrated fluid management module for use in a magnetorheological finishing system having a carrier wheel, comprising: (a) a housing having a magnetically-shielded chamber therein, said chamber having an opening configured to be disposed to a surface of said carrier wheel; (b) apparatus for receiving and replenishing spent magnetorheological fluid within said chamber; and (c) a ribbon extruder mounted to said housing for extruding a ribbon of replenished magnetorheological fluid from said chamber onto said wheel surface, wherein said replenishing apparatus comprises a sensor system for sensing concentration of magnetic particles in magnetorheological fluid comprising: (a) a sensor disposed in a wall of chamber in contact with mixed and replenished magnetorheological fluid; (b) a first wire coil; (c) an AC voltage generator attached to said first wire coil in an electrical circuit, such that when said generator is energized a magnetic flux field is created in and around said first wire coil, wherein said magnetic flux field includes fringing fields extending beyond the opposite ends of said first wire coil and, such that in use either but not both of said fringing fields extends beyond the opposite ends of said first wire coil and also extends through said magnetorheological fluid; (d) a second wire coil connected to said generator and identical to said first wire coil and having fringing fields outside of said magnetorheological fluid, wherein said first wire coil is a sensing coil and said second wire coil is a reference coil; (e) a demodulator connected to said sensing coil and said reference coil and configured to provide a signal that is proportional to the concentration of magnetic particles; (f) a controllable dispensing apparatus for adding a calculated amount of replenishing fluid to said magnetorheological fluid; and (g) a feedback controller connected to said demodulator for sending signals to said controllable dispensing apparatus. (a) a housing having a magnetically-shielded chamber therein, said chamber having an opening configured to be disposed to a surface of said carrier wheel; (b) apparatus for receiving and replenishing spent magnetorheological fluid within said chamber; and (c) a ribbon extruder mounted to said housing for extruding a ribbon of replenished magnetorheological fluid from said chamber onto said wheel surface, wherein said replenishing apparatus comprises a sensor system for sensing concentration of magnetic particles in magnetorheological fluid comprising: (a) a sensor disposed in a wall of chamber in contact with mixed and replenished magnetorheological fluid; (b) a first wire coil; (c) an AC voltage generator attached to said first wire coil in an electrical circuit, such that when said generator is energized a magnetic flux field is created in and around said first wire coil, wherein said magnetic flux field includes fringing fields extending beyond the opposite ends of said first wire coil and, such that in use either but not both of said fringing fields extends beyond the opposite ends of said first wire coil and also extends through said magnetorheological fluid; (d) a second wire coil connected to said generator and identical to said first wire coil and having fringing fields outside of said magnetorheological fluid, wherein said first wire coil is a sensing coil and said second wire coil is a reference coil; (e) a demodulator connected to said sensing coil and said reference coil and configured to provide a signal that is proportional to the concentration of magnetic particles; (f) a controllable dispensing apparatus for adding a calculated amount of replenishing fluid to said magnetorheological fluid; and (g) a feedback controller connected to said demodulator for sending signals to said controllable dispensing apparatus. (a) a sensor disposed in a wall of chamber in contact with mixed and replenished magnetorheological fluid; (b) a first wire coil; (c) an AC voltage generator attached to said first wire coil in an electrical circuit, such that when said generator is energized a magnetic flux field is created in and around said first wire coil, wherein said magnetic flux field includes fringing fields extending beyond the opposite ends of said first wire coil and, such that in use either but not both of said fringing fields extends beyond the opposite ends of said first wire coil and also extends through said magnetorheological fluid; (d) a second wire coil connected to said generator and identical to said first wire coil and having fringing fields outside of said magnetorheological fluid, wherein said first wire coil is a sensing coil and said second wire coil is a reference coil; (e) a demodulator connected to said sensing coil and said reference coil and configured to provide a signal that is proportional to the concentration of magnetic particles; (f) a controllable dispensing apparatus for adding a calculated amount of replenishing fluid to said magnetorheological fluid; and (g) a feedback controller connected to said demodulator for sending signals to said controllable dispensing apparatus.