1) The zener impedance is derived from the 60Hz AC voltage which results when an AC current having an RMS value equal to 10% of the Zener current (IZT or IZK) is
superimposed on IZT or IZK Zener impedance is measured at two points to insure a sharp knee on the breakdown curve and to elimunate unstable units.
2) Valid provided that leads at a distance of 8mm from case are kept at ambient temperature.
3) Measured under thermal equilibrium and DC test conditions.