Tektronix TCP300 Series, User Manual, Page: 56 / 80

Application Notes
Measuring Inductor Turns Count
To obtain an approximate turns count of an inductor, do the following. (See
Figure 23.)
1. Connect the inductor to a current limited source, as shown.
2. Measure the input current on one of the inductor leads.
3. Clamp the current probe around the inductor and note the current value.
Figure 23: Measuring the number of turns in a coil
The number of turns is equal to the ratio of coil current to input current. The
accuracy of this method is limited by the current measurement accuracy. The
following method allows more precise turns measurement.
For a more precise turns count, you need a coil with a known number of turns
to use as a reference.
1. Repeat steps 1 and 2 above and make the following changes:
2. Insert the reference coil into the current probe.
3. Insert the test coil into the current probe so that the currents oppose each other
as shown. (See Figure 24.)
Figure 24: Turns measurement using reference coil
38 TCPA300/400 Ampli fi ers and TCP300/400 Series Current Probes User Manual