1. A contact detection apparatus for a wire electrical discharge machine, said apparatus comprising:
a voltage application unit configured to apply a detection voltage to detect contact between a wire electrode and a workpiece
during non-machining periods;
a contact determination unit configured to determine contact or non-contact between the wire electrode and the workpiece based
on changes in the detection voltage applied by the voltage application unit; and
a controller configured to change, during the non-machining periods, a voltage value of the detection voltage applied by the
voltage application unit according to a property of the workpiece.