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4. ExPLaNatIoN of SymboLS
The triangle containing a lightning symbol warns against danger of electrical shock
or impairment of the electrical safety of the device.
The exclamation mark in a triangle indicates important notes in these operating
instructions that must be observed strictly.
The arrow symbol indicates that special advice and notes on operation are provided.
Protection Class 2 (double or enforced insulation, protected insulation).
Cat I
Measurement Category I is for measuring electrical and electronic equipment,
which is not directly supplied with mains voltage, such as battery-powered
devices, protected low voltage, signal and control voltages etc.
Cat II
Measurement Category II is for measuring electrical and electronic equipment,
which is supplied with mains voltage directly by a power plug. Included in this
category are the lower categories (e.g. CAT I for measuring signal and control
voltages).
Cat III
Measurement Category III is for measuring installations in buildings, such as
socket-outlets or sub-distributions. Included in this category are the lower catego-
ries (e.g. CAT II for measurements on electrical appliances). Measurement in CAT
III is only permitted when test probes with a maximum contact-free length of 4 mm
or caps covering the probe tips are used.
Cat IV
Measurement Category IV is for measuring the source of low voltage installations
such as main distributions, house-transfer points of utilities etc, and outdoors (e.g.,
work on underground cables, overhead lines etc.). Included in this category are
the lower categories. Measurement in CAT IV is only permitted when test probes
with a maximum contact-free length of 4 mm or with caps covering the probe tips
are used.
