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iv 34401A User’s Guide
WARNING
IEC Measurement Category II. The
HI and LO input terminals may be
connected to mains in IEC Cate-
gory II installations for line volt-
ages up to 300 VAC. To avoid the
danger of electric shock, do not
connect the inputs to mains for
line voltages above 300 VAC. See
"IEC Measurement Category II
Overvoltage Protection" on the
following page for further infor-
mation.
WARNING
Protection Limits: To avoid instru-
ment damage and the risk of elec-
tric shock, do not exceed any of
the Protection Limits defined in
the following section.
Protection Limits
The Agilent 34401A Digital Multimeter pro-
vides protection circuitry to prevent damage
to the instrument and to protect against the
danger of electric shock, provided the Pro-
tection Limits are not exceeded. To ensure
safe operation of the instrument, do not
exceed the Protection Limits shown on the
front and rear panel, and defined as follows:
Note: The front-panel terminals are shown
above. The rear-panel terminals are identi-
cal. The Front/Rear switch selects the ter-
minal set to be used. Do not operate this
switch while signals are present on the
front or rear terminals. The current-protec-
tion fuse is on the rear panel.
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, frequency (period), and diode
test measurements. Two Protection Limits
are defined for these terminals:
HI to LO Protection Limit. The Protection
Limit from HI to LO (Input terminals) is
1000 VDC or 750 VAC, which is also the
maximum voltage measurement. This
limit can also be expressed as 1000 Vpk
maximum.
LO to Ground Protection Limit. The LO
input terminal can safely "float" a maxi-
mum of 500 Vpk relative to ground.
As is implied by the above limits, the Protec-
tion Limit for the HI input terminal is a maxi-
mum of 1500 Vpk relative to ground.
Current Input Terminal. The current input
("I") terminal has a Protection Limit of 3A
(rms) maximum current flowing from the LO
input terminal. Note that the current input
terminal will be at approximately the same
voltage as the LO terminal.
Note: The current-protection circuitry
includes a fuse on the rear panel. To main-
tain protection, 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 and tempera-
ture measurements ("
Ω 4W"). The Protec-
tion Limit is 200 Vpk for all of the terminal
pairings:
LO sense to LO input
HI sense to LO input
HI sense to LO sense
Note: The 200 Vpk limit on the sense termi-
nals is the Protection Limit. Operational
voltages in resistance measurements are
much lower — less than 10 V in normal
operation.
IEC Measurement Category II
Overvoltage Protection
To protect against the danger of electric
shock, the Agilent 34401A Digital Multime-
ter provides overvoltage protection for
line-voltage mains connections meeting
both of the following conditions:
The HI and LO input terminals are con-
nected to the mains under Measurement
Category II conditions, defined below,
and
The mains are limited to a maximum line
voltage of 300 VAC.