Wiring The Circuit Under Measurement When Using Current Sensors - YOKOGAWA WT1800 User Manual

2.10 Wiring the Circuit under Measurement When
Using Current Sensors
To prevent electric shock and damage to the instrument, follow the warnings given in section 2.5,
"Precautions When Wiring the Circuit under Measurement."
If the maximum current of the circuit under measurement exceeds the maximum range of the input
elements, you can measure the current of the circuit under measurement by connecting an external
current sensor to the external current sensor input connector.
• 5 A input elements
When the maximum current exceeds 5 Arms
• 50 A input elements
When the maximum current exceeds 50 Arms
Current Sensor Output Type
• If you are using a shunt-type current sensor or a clamp-type current sensor that outputs voltage as
the external current sensor, see the wiring examples in this section.
• If you are using a clamp-type current sensor that outputs current, see section 2.11.
Connecting to the Input Terminal
External Current Sensor Input Terminal
Connect an external current sensor cable with a BNC connector (B9284LK, sold separately) to an
external current sensor input connector.
Remove the measurement cable connected to the current input terminal. Because the external current
sensor input terminal and the current input terminal are connected internally, connecting both terminals
simultaneously not only results in measurement errors but may also cause damage to the instrument.
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.
Note
• The thick lines on the wiring diagrams are the parts where the current flows. Use wires that are suitable
for the current levels.
• To measure the apparent power and power factor more accurately on an unbalanced three-phase circuit,
we recommend that you use a three-phase, three-wire system that uses a three-voltage, three-current
method (3P3W; 3V3A).
• Note that the frequency and phase characteristics of the current sensor affect the measured data.
• Make sure that you have the polarities correct when you make connections. If the polarity is reversed,
the polarity of the measurement current will be reversed, and you will not be able to make correct
measurements. Be especially careful when connecting clamp-type current sensors to the circuit under
measurement, because it is easy to reverse the connection.
• To minimize error when using shunt-type current sensors, follow the guidelines below when connecting
the external current sensor cable.
• Connect the shielded wire of the external current sensor cable to the L side of the shunt output terminal
(OUT).
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IM WT1801-03EN