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Chapter 4 Measurement
4.3 Before Measurement
This section describes notes on accuracy and the handling of the Rogowski
Coil Sensor when measuring the current using this instrument.
4.3.1 To Achieve Accurate Measurement
As explained in Chapter 3 "Measurement Principle," the Rogowski Coil is a
wire rod wound tight around a tube-like wick material, as illustrated in Figure
3.1. When this coil is uniformly rolled and the ring compound shuts
completely, all the magnetic flux changes by the electric current that passes
in the Rogowski Coil can be detected. In this case, even if the position of the
measured electric current is not placed at a center of the coil, the error
margin is not caused. Moreover, the external magnetic field can be canceled.
However, it doesn't become structurally a complete ring compound because
there is a connecting part in the Rogowski Coil.
For reference, Figure 4.3 shows the position of the connection of the
Rogowski Coil.
The connection of the Rogowski Coil is in the center of the dotted circle. It is
known that a measurement error becomes larger because the variation of
the magnetic flux that cannot be detected increases as the current to be
measured comes closer to this part. Avoid measuring current in the dotted
area, because a measurement error of −4% or more may be caused by the
measurement performed in the area. In addition, there is a possibility that the
measurement error grows because of an external magnetic flux that similarly
hangs to the connecting part. Before measuring current, place conductors in
which current flows other than the conductor to be measured away from the
Rogowski Coil connection as much as possible.
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Figure 4.3 Rogowski Coil Connection
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