In this paper, the dependence of magnetic properties of amorphous ribbons and wires on aging is shown. Aging process is simulated by acid attack and thermal oxidation while coercive H c and remanence B r are measured by a stationary-coil magnetometer. The main conclusion is that H c and B r are stabilized after acid attack of H 2 SO 4 solution with pH 2 for 2h and corresponding oxidation in 350 o C in free air for 2h. Thus, the uncertainty of inductive sensors based on coercivity and remanence of amorphous ribbons and wires can be determined with respect to time.