The 50 mm diameter test sphere is one of the oldest accessibility checks in IEC 60529, yet it is routinely misapplied. The plain sphere and the sphere fitted with a 50 mm x 50 mm square ring are not the same test, and confusing them produces a result that answers the wrong question.
The rigid 50 mm sphere, usually with a handle, checks that a large object - roughly the size of a child's fist - cannot enter the enclosure and reach hazardous parts. It is a blunt check: if the sphere passes through an opening, that opening is too large for the declared degree of protection.
The same sphere carrying a 50 mm square ring is used to judge whether an opening gives access to a rigid object. The ring stops the sphere from being pushed through a slot or mesh by presenting the full square face. This separates "the sphere fits through the hole" from "the sphere can be forced through the hole."
The sphere is about object size, not finger simulation. The jointed test finger models a person's finger and is the right tool when accessibility by touch is the question. Reaching for the sphere where a finger probe is meant - or the reverse - gives a number that does not satisfy the compliance clause.
Use the sphere with its own weight only, no extra push. If it enters and can reach live parts, the enclosure fails that degree of protection. Write down which variant was used; the pass or fail answer depends on it.
Treating a mesh that stops the sphere as proof against smaller probes; using the ringed sphere where a plain one is specified; and assuming a pass against the 50 mm sphere means the product is safe against thinner tools. None of those follow from the test.
