Application Reference
High impedance pulse
source
If the pulse source has a higher impedance of known resistance, and the output voltage
drops as the current increases, the inductance of the coil can be calculated from the time
constant of the charging curve. The current ramp shows how to derive the formula value
for the inductance. Use this formula to calculate the inductance from the current
measurement:
L =
τ
R
The L
is the inductance in Henrys. τ
is the time required for the current to rise or fall to
63.2% of the total current value, and R is the source resistance of the pulse generator.
Measuring Inductor Turns
To get the approximate number of turns for the inductor, follow these steps:
1. Connect the inductor to the current limited power supply, shown as below.
2. Measure the input current in one of the inductor leads.
3. Clip the current probe to the inductor and record the current value.
The number of turns is equal to the ratio of the coil current to the input current. The
accuracy of this method will be limited by the current measurement accuracy.
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