Only test equipment suited to the test may be used, following its operating instructions, and it should be checked before each use for condition, cleanliness, intact leads, probes and clips, and correct operation. The combination of instrument and leads should withstand the highest voltage at the test location: category I for ELV circuits not directly connected to mains (not for LV installations), II for appliances, III for final subcircuits, distribution boards, submains and LV d.c., and IV at the origin of an LV installation, for example main switchboards (category III or IV instruments are recommended for general use). Test equipment used in hazardous areas must be marked as suitable; probes and leads must be chosen so they cannot bridge live parts or live parts and earth; and terminals must be shrouded when testing for de-energization (HB 187 helps with multimeter selection).
The graph holds this control, the 0 it maps to, and the evidence behind each claim, over MCP and REST.