Hioki ST5540, Instruction Manual, Page: 20 / 326

1.6 Types of Leakage Current Measurement
14
Class-I equipment does not require the measurement of enclosure leakage current since metal enclo-
sures must be grounded for electrical protection. However, when the protective earth conductor becomes
disconnected (single fault), the enclosure is no longer grounded for protection and must be measured.
For
Class-II equipment, all enclosures are ungrounded for electrical protection and must be tested.
Ungrounded equipment are often made of plastics and other insulated materials. Since leakage current
flows through the human body, the standard stipulates that a probe is applied to metal foil the size of a
hand pressed against the insulated material. Use the 9195 enclosure probe supplied with the instrument
for measurements involving this instrument.
There are two paths for touch current to flow: "enclosure

human body

earth" and "enclosure

human body

enclosure." Note that for "enclosure

human body

enclosure" to occur a person
must touch two electrically isolated (separate) enclosure sections not two sections on the same enclo-
sure.
Touch current measurement