Tektronix TCP300 Series, User Manual, Page: 49 / 80

Reference Notes
NOTE.
Adding a second conductor to the probe increases the insertion impedance
and reduces the upper bandwidth limit of the probe.
You can increase the value of the bucking current by winding multiple turns of the
second conductor around the probe, as shown in the illustration. (See Figure 16.)
Figure 16: Adding multiple turns
The bucking current is equal to the current fl owing in the conductor, multiplied
by the number of turns wound around the probe. For example, if the second
conductor has a current of 100 mA DC and is wrapped around the probe
fi ve
times, the DC bucking current is 100 mA multiplied by 5, or 500 mA DC.
To determine measurement values, add the value of the bucking current to the
displayed measurement.
NOTE.
Winding multiple turns to the probe increases the insertion impedance and
reduces the upper bandwidth limit of the probe.
Extending AC Range You can extend the AC amplitude limit of the TCPA300 by using the Tektronix
CT-4 High-Current Transformer. The CT-4, designed for use with the TCP305
and TCP312 current probes, extends the current probe range by a factor of 20:1
or 1000:1. The CT-4 can provide external steady-state DC bucking current up
to 300 A. For more information about the CT-4, consult your Tektronix sales
representative.
Because the CT-4 has a lower AC bandwidth limit than the TCP305 and TCP312
current probes, set the ampli
fi er coupling to DC when using the CT-4.
TCPA300/400 Ampli fi ers and TCP300/400 Series Current Probes User Manual 31