Probe responsive to conditions of material

Claim 1

A probe system responsive to the condition of materials comprising: conductive means having materials juxtaposed thereto; and a probe apparatuss comprising: a conductive probe electrode; solid insulation means; a hollow conductive guard shield having outer walls forming an interior cavity receiving said probe electrode, said guard shield being electrically insulated from said probe electrode and said conductive means by said solid insulation means; and said solid insulation means contacting said guard shield, one portion of said insulation means supporting said probe electrode on said guard shield and another portion of said insulation means extending outwardly beyond said outer walls, said guard shield being interposed between said one portion and said other portion so as to substantially eliminate any current leakage path through said solid insulation means from said probe electrode through said other portion; said outer walls having a surface not covered by said insulation means so as to be exposed to direct contact with the materials, said exposed surface having an overall length measured in a direction from said probe electrode to said insulation means along a surface of said probe apparatus exposed to direct contact with the materials, said overall length being substantially greater than the minimum thickness of said outer walls of said guard shield.