Wire-dot impact printer

A wire-dot impact printer comprising:

• a wire-dot print head composed of:
• armatures each of which carries a print wire fixed on a free end thereof;
• leaf springs supporting thereon the armatures, respectively;
• cores arranged opposite the respective armatures;
• a permanent magnet arranged to produce a magnetic flux, each armature being attracted by the magnet toward the associated core against a resilient force provided by the corresponding leaf spring;
• coils wound around the cores, respectively, each coil producing upon energization a magnetic flux to cancel out the magnetic flux of the permanent magnet so that the corresponding armature is released from the associated core;
• sensor electrodes formed on a printed circuit board located opposite the armatures, said sensor electrodes being disposed with intervals between the sensor electrodes and the corresponding armatures, each sensor electrode forming a portion of a first variable capacitor;
• and
• noise-canceling electrodes, one noise-cancelling electrode arranged around each respective sensor electrode, each noise-cancelling electrode forming a portion of a second variable capacitor;
• a first capacitance detector arranged to detect a displacement of each armature by the corresponding sensor electrode located opposite the armature;
• and
• a second capacitance detector arranged to detect a noise potential on the armature by the corresponding noise-cancelling electrode.