Probe tubes may be clad, plated, or left unplated, depending on the intended application. The following is a summary of the various options and their applications:
"N" Style Probe Tube: This nickel silver tube with no cladding or plating is suitable for most bare board test applications where probe resistance below one ohm is acceptable, or when cost is an issue. Oxides which form on the inside surface of the tube can impede current flow between the tube and plunger.
"G" Style Probe Tube: This tube is a nickel silver tube with a layer of gold plating on the outside surface of the tube. On larger center probes, the plating also
covers the inside of the probe tube and improves performance
considerably compared to the “N” tube.
"P" Style Probe Tube: This tube is deep-drawn from nickel silver alloy with precious metal
clad on the inside surface, and is used for in-circuit testing where low and
consistent electrical resistance is necessary. The deep-drawing process
hardens the gold, improving wear characteristics and results in a gold
layer of extremely uniform thickness along the entire inside surface of
"H" Style Probe Tube: This tube is made from a proprietary, high conductivity alloy, gold plated. These tubes are used in high current applications, very humid
environments, or where extremely low electrical resistance is required.