Keysight 34450A Guia Del Usuario página 7

Protection Limits
The Keysight 34450A 5½ Digital
Multimeter provides protection circuitry
to prevent damage to the instrument
and to protect against the danger of
electric shock, provided that the
Protection Limits are not exceeded. To
ensure safe operation of the
instrument, do not exceed the
Protection Limits shown on the front
panel, as defined below:
E
B
D
Note: The front-panel terminals and
current protection fuse are shown
above.
Input Terminal Protection
Limits
Protection Limits are defined for the
input terminals:
Main Input (HI and LO) Terminals. The
HI and LO input terminals are used for
voltage, resistance, capacitance, and
diode test measurements. Two
Protection Limits are defined for these
terminals:
HI to LO Protection Limit. The
Protection Limit from HI to LO ("A" in
the figure above) is 1000 VDC or 750
VAC, which is also the maximum
voltage measurement. This limit can
also be expressed as 1000 Vpk
maximum.
Keysight 34450A User's Guide
LO to Ground Protection Limit. The
LO input terminal can safely "float" a
maximum of 500 Vpk relative to
ground. This is Protection Limit "B" in
the figure.
Although not shown on the figure, the
Protection Limit for the HI terminal is a
maximum of 1000 Vpk relative to the
ground. Therefore, the sum of the
"float" voltage and the measured
voltage must not exceed 1000 Vpk
Current Input Terminal. The current
input ("I") terminal has a Protection
Limit of 100 mA (rms) maximum current
flowing from the LO input terminal. This
is Protection Limit "C" in the figure.
Note that the current input terminal will
be at approximately the same voltage
A
as the LO terminal.
Note: The current-protection circuitry
includes a fuse on the back panel. To
maintain protection, replace this fuse
only with a fuse of the specified type
C
and rating.
10 A Current Input Terminal. The 10 A
current input terminal has a Protection
Limit of 10 A (rms) maximum current
flowing from the LO input terminal. This
is Protection Limit "D" in the figure.
Note that the current input terminal will
be at approximately the same voltage
as the LO terminal.
Note: The current-protection circuitry
includes an internal fuse. To maintain
protection, service-trained personnel
should replace this fuse only with a fuse
of the specified type and rating.
Sense Terminal Protection
Limits
The HI and LO sense terminals are used
only for four-wire resistance

measurements ("
Protection Limit is 200 Vpk for all of the
terminal pairings ("E" in the figure):
LO sense to LO input.
HI sense to LO input.
HI sense to LO sense.
Note: The 200 Vpk limit on the sense
terminals is the Protection Limit.
Operational voltages in resistance
measurements aremuch lower - less
than 5 V in normal operation.
IEC Measurement Category
II Overvoltage Protection
To protect against the danger of
electric shock, the Keysight 34450A 5½
Digital Multimeter provides overvoltage
protection for line-voltage mains
connections meeting both of the
following conditions:
The HI and LO input terminals are
connected to the mains under
Measurement Category II conditions,
defined below, and
The mains are limited to a maximum
line voltage of 300 VAC.
IEC Measurement Category II includes
electrical devices connected to mains at
an outlet on a branch circuit. Such
devices include most small appliances,
test equipment, and other devices that
plug into a branch outlet or socket. The
34450A may be used to make
measurements with the HI and LO inputs
connected to mains in such devices, or to
the branch outlet itself (up to 300 VAC).
However, the 34450A may not be used
with its HI and LO inputs connected to
mains in permanently installed electrical
devices such as the main circuit-breaker
panel, sub-panel disconnect boxes, or
permanently wired motors. Such devices
and circuits are subject to overvoltages
that may exceed the protection limits of
the 34450A.
Note: Voltages above 300 VAC may be
measured only in circuits that are
isolated from mains. However, transient
overvoltages are also present on
4W"). The
circuits that are isolated from mains.
The 34450A is designed to safely
withstand occasional transient
overvoltages up to 2500 Vpk. Do not
use this multimeter to measure circuits
where transient overvoltages could
exceed this level.
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