A magnetoplated wire (MPW) is a copper wire whose circumference is plated with a magnetic thin film. The effects of using an MPW are a decrease in the proximity effect, an increase in inductance, and generation of more flux than when copper wire is used. The ratio of the linearity range Lo to the outer coil diameter D of the eddy current displacement sensor is extended by using MPW for the coil. However, the relationship between the Fe film thickness of MPWs and the linearity range characteristic has not been clarified. We measured the output voltage characteristics of MPW coils with Fe film thicknesses of 0.7 μm, 1 μm, and 1.1 μm, and calculated Lo/D ratios. As a result, we found that the Lo/D ratio of an MPW coil with a 1-μm-thick Fe film had a maximum value of 0.66.
