A circuit is described which permits a hysteretic ratio to be graphed versus another experimental parameter. The hysteretic ratio can be defined either: (a) by the two discontinuities of theI–Vresponse (or more exactly the two discontinuities in (dV/dt) or (b) by the two polarity changes (as in ferromagneticBvsHcurves). The circuit features a large dynamic range (≳40 dB with no adjustments) and works well for modulation frequencies between 10−3and 300 Hz.