A probe needle apparatus and method provides a drive guard having the same
potential as a probe needle for reducing signal noise in low current
measurements. The probe needle apparatus includes a conductive central
core covered with alternating layers of dielectric and conductive
materials, a first layer of dielectric material applied to maintain
electrical access to the conductive central core while providing
continuous isolation of the conductive central core elsewhere, and a
conductive driven guard layer applied around the first layer of
dielectric material in electrical isolation from the conductive central
core.