Tektronix TCPA300 SERIES, Instruction Manual

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Application Notes
3- 14
TCPA300/400 Amplifiers and TCP300/400 Series Current Probes Instruction Manual
d
i
d
t
Time (t)
Current
flow (i)
Figure 3- 10: Linear current vs. time ramp
If the pulse source has a higher impedance of known resistance, such that the
output voltage drops as the current increases, the inductance of a coil can be
calculated by the time constant of the charge curve. Figure 3--11 shows the setup
diagram, which is similar to the previous example. The current ramp represented
in Figure 3--12 shows how the values for the inductance formula are obtained.
Use this formula to calculate the inductance based on the current measurement:
L = τ R
where L is the inductance in henries,
τ
is the time required for the current to rise
or fall 63.2% of the total current value, and R is the source resistance of the pulse
generator.
High-Impedance Pulse
Sources