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Safety Information
Overvoltage Categories (CAT)
This instrument complies with CAT II (power supply section) safety
requirements.
To ensure safe operation of measurement instruments, IEC 60664
establishes safety standards for various electrical environments,
categorized as CAT I to CAT IV, and called overvoltage categories.
These are defined as follows.
Higher-numbered categories correspond to electrical environments
with greater momentary energy. So a measurement device designed
for CAT III environments can endure greater momentary energy than a
device designed for CAT II.
Using a measurement instrument in an environment designated with a
higher-numbered category than that for which the instrument is rated
could result in a severe accident, and must be carefully avoided.
Accuracy We define measurement tolerances in terms of f.s. (full scale), rdg.
(reading) and dgt. (digit) values, with the following meanings:
CAT I
Secondary electrical circuits connected to an AC electrical
outlet through a transformer or similar device.
CAT II
Primary electrical circuits in equipment connected to an AC
electrical outlet by a power cord (portable tools, household
appliances, etc.)
CAT III
Primary electrical circuits of heavy equipment (fixed
installations) connected directly to the distribution panel, and
feeders from the distribution panel to outlets.
CAT IV
The circuit from the service drop to the service entrance, and
to the power meter and primary overcurrent protection device
(distribution panel).
f.s.
(maximum display value or scale length)
The maximum displayable value or scale length. This is usually the
name of the currently selected range.
rdg.
(reading, displayed or indicated value)
The value currently being measured and indicated on the measuring
instrument.
dgt.
(resolution)
The smallest displayable unit on a digital measuring instrument, i.e.,
the input value that causes the digital display to show a "1" as the
least-significant digit.
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