Thin-Flexi Current Probe - Fluke FL1730-BAS User Manual

1730
Users Manual

Thin-Flexi Current Probe

The Thin-Flexi Current Probe works on the Rogowski coil
(R-coil) principle that is a toroid of wire used to measure
an alternating current through a cable encircled by the
toroid. See Figure 4.
i(t)
Figure 4. R-Coil Operation Principle
10
R1
330 k
R3 V
10 k
A out
C1
10 nF
V
in
UI:A
2
v(t)
1
3
LF347
GND
The R-coil has many 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.
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