Hioki ST5540, Instruction Manual, Page: 10 / 326

4
Accuracy
We define measurement tolerances in terms of f.s. (full scale), rdg. (reading) and dgt. (digit) values, with
the following meanings:
This instrument complies with CAT II (300 V) safety requirements.
To ensure safe operation of measurement instruments, IEC 61010 establishes safety standards for vari-
ous electrical environments, categorized as CAT II to CAT IV, and called measurement categories.
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.
Use of a measurement instrument that is not CAT-rated in CAT II to CAT IV measurement applications
could result in a severe accident, and must be carefully avoided.
Other Symbols
Indicates a prohibited action.
See Indicates the location of reference information.
*
Indicates that descriptive information is provided below.
(Example)
Leakage current
For information on text in italics, refer to "Appendix1 Terminology" (p. A1).
Indicates descriptions relating to the RS-232C only.
Indicates descriptions relating to the USB only.
USB
f.s. (maximum display
value):
The maximum displayable value. This is usually the name of the currently selected range.
rdg. (reading or
displayed 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.
Measurement categories
CAT II :
Primary electrical circuits in equipment connected to an AC electrical outlet by a power cord (portable tools,
household appliances, etc.)
CAT II covers directly measuring electrical outlet receptacles.
CAT III : Prima ry electrical circuits o f 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 pro-
tection device (distribution panel).