Precautions For Wiring The Circuit That You Will Measure - YOKOGAWA WT500 User Manual

3.5 Precautions for Wiring the Circuit That You Will
Measure
3-8
To avoid electric shock and damage to the instrument, follow the precautions below.
• Ground the instrument before connecting measurement cables. The power cord
that comes with the instrument is a three-prong cord. Insert the power cord into
a grounded three-prong outlet.
• Turn off the power to the circuit under measurement when wiring or
disconnecting it. Connecting or removing measurement cables while the power
is on is dangerous.
• Do not wire a current circuit to the voltage input terminal or a voltage circuit to
the current input terminal.
• Strip the insulation covers of measurement cables so that when they are wired
to the input terminals, the conductive parts (bare wires) do not protrude from the
terminals. Also, make sure to fasten the input terminal screws securely so that
cables do not come loose.
• Only connect cables that have safety terminals that cover the conductive parts
to the voltage input terminals. Using a terminal with bare conductive parts (such
as a banana plug) can be dangerous if the terminal comes loose.
• Only connect cables that have safety terminals that cover the conductive parts
to the current sensor input terminals. Using a terminal with bare conductive parts
(such as a banana plug) is dangerous if the terminal comes loose.
• When the voltage from the circuit under measurement is being applied to the
current input terminals, do not touch the current sensor input terminals. Doing
so is dangerous because the terminals are electrically connected inside the
instrument.
• When connecting a measurement cable from an external current sensor to a
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 a current sensor input terminal, do not touch the current
input terminals. Doing so is dangerous because the terminals are electrically
connected inside the instrument.
• When using an external voltage transformer (VT) or current transformer (CT),
make sure that it has enough dielectric strength for 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 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 dielectric strength for the voltage being measured. Using a
bare sensor is dangerous, because you might accidentally touch it.
• When using a shunt-type current sensor as an external current sensor, turn off
the circuit under measurement. Connecting or removing the sensor while the
power is on is dangerous.
• When using a clamp-type current sensor as an external current sensor, confirm
that there are no shock hazards, after making sure that you understand the
voltage of the circuit under measurement and the specifications and handling of
the clamp-type sensor.
• For safety reasons, when using the instrument on a rack mount, set up a switch
for turning off the circuit under measurement from the front side of the rack.
• After connecting measurement cables, attach the current input protection cover
using the screws provided. Make sure that the conductive parts do not protrude
from the protection cover.
WARNING
IM 760201-01E