3 Phase Power Quality Analyzer
Before You Start
9
iFlexi Current Probe
The iFlexi Current Probe works on the Rogowski coil (R-coil) principle that is a toroid of wire
used to measure an alternating current through a wire encircled by the toroid. See Figure 5.
Figure 5. R-Coil Operation Principle
The R-coil has advantages over other types of current transformers:
It is not a closed loop. The second terminal is passed back through the center of the toroid
core (commonly a plastic or rubber tube) and connected along the first terminal. This allows
the coil to be open-ended, flexible, and able to be wrapped around a live conductor without
disturbing it.
It has an air core rather than an iron core. It has a low inductance and can respond to fast-
changing currents.
Because it has no iron core to saturate, it is highly linear even when subjected to large
currents, such as those used in electric power transmission or pulsed-power applications.
A correctly formed R-coil, with equally spaced windings, is largely immune to electromagnetic
interference.
i(t)
v(t)
A
r
10 k R3
330 k R1
10 nF C1
LF347
UI:A
1
GND
2
114
3
V
in
V
out
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