YOKOGAWA WT1800 User Manual page 11

Wiring
Power meters can measure large voltages and currents directly. If you use a voltage
transformer or a current transformer together with this power meter, you can measure even
larger voltages or currents. When you are measuring a large voltage or current, the power
capacity of the item under measurement becomes large. If you do not connect the cables
correctly, an overvoltage or overcurrent may be generated in the circuit under measurement.
This may lead to not only damage to the power meter and the item under measurement, but
electric shock and fire as well. Be careful when you connect the cables, and be sure to check
the following points.
Before you begin measuring (before you turn the item under measurement on), check that:
• Cables have been connected to the power meter's input terminals correctly.
Check that there are no voltage measurement cables that have been connected to the
current input terminals.
Check that there are no current measurement cables that have been connected to the
voltage input terminals.
If you are measuring multiphase power, check that there are no mistakes in the phase
wiring.
• Cables have been connected to the power supply and the item under measurement
correctly.
Check that there are no short circuits between terminals and between connected cables.
• The cables are connected firmly to the current input terminals.
• There are no problems with the current input terminals and the crimping terminals, such as
the presence of foreign substances.
During measurement (never touch the terminals and the connected cables when the item
under measurement is on), check that:
• There no problems with the input terminals and the crimping terminals, such as the
presence of foreign substances.
• The input terminals are not abnormally hot.
• The cables are connected firmly to the input terminals.
The terminal connections may become loose over time. If this happens, heat may be
generated due to changes in contact resistance. If you are going to take measurements
using the same setup for a long time, periodically check that the cables are firmly
connected to the terminals. (Be sure to turn both the power meter and the item under
measurement off before you check the connections.)
After measuring (immediately after you turn the item under measurement off):
After you measure a large voltage or current, power may remain for some time in the item
under measurement even after you turn it off. This remaining power may lead to electric
shock, so do not touch the input terminals immediately after you turn the item under
measurement off. The amount of time that power remains in the item under measurement
varies depending on the item.
Operating Environment Limitations
This product is a Class A (for industrial environments) product. Operation of this product in a
residential area may cause radio interference in which case the user is required to correct the
interference.
IM WT1801-03EN
CAUTION
Safety Precautions
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