YOKOGAWA WT210, User Manual, Page: 53 / 316

3-4
IM 760401-01E
3.3 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-pin outlet.
• To ensure safe operation, if the current to be measured exceeds 7 A (rms
value), use a cable or conductor that is capable of running a current higher than
the current to be measured, and be sure to connect the protective earth before
operating the instrument. The protective earth terminal is provided on the rear
panel of products shipped in January 2004 and later.
• Take special caution not to wire a current measurement circuit to the voltage
input terminal or a voltage measurement circuit to the current input terminal.
• Strip the insulation cover of the measurement cable so that when it is wired to
the current input terminal, the conductive parts (bare wires) do not protrude from
the terminal. Also, make sure to fasten the current 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 when the terminal comes loose.
• Use cables with safety terminals that cover the conductive parts for connecting
to the current sensor input connectors (external sensor input connectors). Using
a terminal with bare conductive parts is dangerous when the conector comes
loose.
• When the voltage of the circuit under measurement is being applied to the
current input terminals, do not touch the external sensor input connector. Since
these terminals are electrically connected inside the instrument, this act is
dangerous.
• When connecting measurement cables from an external current sensor to the
external 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 external sensor input connector, do not touch the current
input terminals. Since these terminals are electrically connected inside the
instrument, this act is dangerous.
• When using the external potential transformer (PT) or current transformer (CT),
make sure it has enough withstand voltage with respect to the voltage (E) being
measured (2E + 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. Otherwise, high voltage will appear at the secondary side of the CT,
making it extremely dangerous.
• 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.