YOKOGAWA wt3000, Руководство пользователя, Страница: 71 / 384

3-7
IM 760301-01E
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App
Index
Before Starting Measurements
3.5 Wiring Precautions
To prevent the possibility of electric shock and damage to the instrument, follow the
warnings below.
WARNING
• Employ protective earth ground before connecting measurement cables. The
power cord that comes with the instrument is a three-pin type power cord.
Connect the power cord to a properly grounded three-prong outlet.
• Turn OFF the power to the circuit under measurement, when wiring or
disconnecting the circuit. Connecting or removing measurement cables while the
power is ON is dangerous.
• Take special caution not to wire a current circuit to the voltage input terminal or
a voltage circuit to the current input terminal.
• Strip the insulation cover of the measurement cable so that when it is wired to
the input terminal, the conductive parts (bare wires) do not protrude from the
terminal. Also, make sure to fasten the input terminal screws securely so that
the cable does not come loose.
• Use cables with safety terminals that cover the conductive parts for connecting
to the voltage input terminals. Using a terminal with bare conductive parts (such
as a banana plug) is dangerous if the terminal comes loose.
• Use cables with safety terminals that cover the conductive parts for connecting
to the current sensor input terminals. Using a terminal with bare conductive
parts is dangerous if the terminal comes loose.
• When the voltage of the circuit under measurement is being applied to the
current input terminals, do not touch the current sensor input terminals. Since
these terminals are electrically connected inside the instrument, this act is dangerous.
• When connecting measurement cables from an external current sensor to the current
sensor input connector, remove the cables connected to the current input terminals. In
addition, when the voltage of the circuit under measurement is being applied to the
current sensor input terminal, do not touch the current input terminals. Since these
terminals are electrically connected inside the instrument, this act is dangerous.
• When using the external voltage transformer (VT) or current transformer (CT), make
sure it has enough withstand voltage with respect to the voltage (U) being measured
(2U + 1000 V recommended). Also, make sure that the secondary side of the CT does
not become an open circuit while the power is being applied. If this happens, high
voltage will appear at the secondary side of the CT, making it extremely dangerous.
• When applying a current exceeding 10 A from a current transformer (CT) to this
instrument, provide protection.
• When using an external current sensor, make sure to use a sensor that comes in a
case. The conductive parts and the case should be insulated, and the sensor should
have enough withstand voltage with respect to the voltage being measured. Using a
bare sensor is dangerous, because you might accidentally come in contact with it.
• When using a shunt-type current sensor as an external current sensor, turn OFF
the circuit under measurement. Connecting or removing a sensor while the power
is ON is dangerous.
• When using a clamp-type current sensor as an external current sensor, have a good
understanding of the voltage of the circuit under measurement and the specifications
and handling of the clamp-type sensor. Then, confirm that there are no shock hazards.
• For safety reasons, when using the instrument on a rack mount, furnish a switch
for turning OFF the circuit under measurement from the front side of the rack.