User Manual

20
Figure 3.9 – Equivalent Inductor Circuit
What is considered high and low impedances to choose the correct circuit
model? There is no exact answer, but generally if the impedance is greater
than 100 Ω* use the parallel circuit model. Use the series circuit model when
the impedance is less than 100 Ω*.
*Note: This is only a typical value. In all cases, it is best to check with the
manufacturer’s data sheet in order to determine the best model to use for
measurement.
The following table translates this approximate impedance rule into
inductance and capacitance values:
Table 3.1 – Series/Parallel Model Guidelines
Frequency
(kHz)
Capacitors
Inductors
Use series
model when
Use parallel
model when
Use series
model when
Use parallel
model when
0.1
> 16 μF
< 16 μF
< 160 mH
> 160 mH
1
> 1.6 μF
< 1.6 μF
< 16 mH
> 16 mH
10
> 160 nF
< 160 nF
< 1.6 mH
> 1.6 mH
100
> 16 nF
< 16 nF
> 160 μH
> 160 μH
Large Inductor
(High Z)
R
P
Less Relevant
L
Small Inductor
(Low Z)
R
P
Relevant
L
R
S
Less Relevant
R
S
Relevant