A simple recording head write field rise time measurement

A very simple technique for measuring the rise time constant of a recording head field is described. More generally the technique measures the time constant for the recording process including the write driver circuit, the head (including micromagnetic effects),and the recording medium dynamics. Unlike other attempts to measure head field rise times, the essence of this approach is the use of the recording medium itself as the sensor. The magnitude of the write current required to produce a readback signal of a given amplitude is measured versus frequency of a square-wave write current. The requisite write current vs. frequency allows the determination of the recording time constant