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IM WT310-02EN
2.11 Wiring the Circuit under Measurement When
Using a Voltage or Current Transformer
This section explains how to wire measurement cables from external voltage transformers
1
or current
transformers
2
to the voltage or current input terminals of input elements. Also refer to this section when
wiring clamp-type current sensors that output current.
*1 VT (voltage transformer)
*2 CT (current transformer)
To prevent electric shock and damage to the instrument, follow the warnings given in section 2.5,
“Precautions When Wiring the Circuit under Measurement.”
Voltage Measurement
When the maximum voltage of the circuit under measurement exceeds 600 Vrms, you can perform
measurements by connecting an external VT to the voltage input terminal.
Current Measurement
If the maximum current of the circuit under measurement exceeds the maximum measurement range,
you can measure the current of the circuit under measurement by connecting an external CT or a
clamp-type sensor that outputs current to the current input terminal.
• WT310 and WT330
When the maximum current exceeds 20 Arms
• WT310HC
When the maximum current exceeds 40 Arms
Connecting to the Input Terminals
Voltage Input Terminals
The terminals are safety banana jacks (female) that are 4 mm in diameter.
Only insert a safety terminal whose conductive parts are not exposed into a voltage input terminal.
If you are using the included 758931 Safety Terminal Adapter, see section 2.6.
Current Input Terminals
• The terminals are binding posts, and the screws are M6. Either wind a wire around a screw or pass
a crimped terminal through the screw axis, and then tighten firmly with the terminal knob.
• For the dimensions of the terminal parts, see section 2.9.
• When the voltage of the circuit under measurement is being applied to the current input terminals,
do not touch the external 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 an external current
sensor input connector, remove the cables connected to the current input terminals. Also, when
the voltage of the circuit under measurement is being applied to the external current sensor input
terminals, do not touch the current input terminals. Doing so is dangerous because the terminals
are electrically connected inside the instrument.
• For the precautions to follow when you connect the current input terminal and the crimping terminal
and after you connect these terminals, see section 2.9.
General VT and CT Handling Precautions
• Do not short the secondary side of a VT. Doing so may damage it.
• Do not short the secondary side of a CT. Doing so may damage it.
Also, follow the VT or CT handling precautions in the manual for the VT or CT that you are using.
