3-21
IM 760301-01E
3
Before Starting Measurements
3.11 Wiring the Circuit under Measurement When
Using the VT/CT
Connect a measurement cable from an external voltage transformer (VT) or current
transformer (CT) to the voltage or current input terminal of the input element. Wire
according to the procedure in this section also when using a clamp-type current sensor
that outputs current.
To prevent the possibility of electric shock and damage to the instrument, follow the
precautions given in section 3.5, “Wiring Precautions.”
An external VT can be connected to the voltage input terminal to make measurements
when the maximum voltage of the circuit under measurement exceeds 1000 Vrms.
If the maximum current of the circuit under measurement exceeds the maximum range of
the input element as described below, measurement can be made by connecting an
external CT or a clamp-type current sensor that outputs current to the current input
terminal.
• 2-A input element
When the maximum current exceeds 2 Arms
• 30-A input element
When the maximum current exceeds 30 Arms
Connecting to the Input Terminal
• Voltage Input Terminal
The terminal is a φ4-mm safety banana jack (female). Insert the safety terminal (the
conductive parts are not exposed) into the voltage input terminal.
When using the 758931 Safety Terminal Adapter that comes with the package, see
section 3.6.
• Current Input Terminal
• 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.
• The screws used on the terminal (binding post) are M6 screws. Use one of the
following methods: wind the wire around the screw, use the 758921 Fork Terminal
Adapter that is sold separately, or pass the crimp-on lugs through the screw axis.
Then, tighten firmly by holding the terminal knob.
• For the dimensions of the parts of the terminal, see section 3.9.
• For precautions during and after connection of the current input terminal and crimp-
on lugs, see section 3.9.
Number of Installed Input Elements and Wiring Systems
The selectable wiring systems vary depending on the number of input elements that are
installed in the instrument. For details, see “Number of Installed Input Elements and
Wiring Systems” in section 2.3, “Measurement Conditions.”
General Handling Precautions of the VT and CT
• Do not short the secondary side of the VT as it may damage the VT.
• Do not open the secondary side of the CT as it may damage the CT.
For other handling precautions of the VT or CT, follow the information that comes with
the VT or CT that you are using.
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