Selection Criteria Of Parallel/Series Equivalent Circuit Models - Keysight E4981A User Manual

Technical Information
Basic Principles of Capacitance Measurement

Selection criteria of parallel/series equivalent circuit models

There are two equivalent circuit models used for capacitance measurement:
parallel mode and series mode, as shown in
these before measurement, depending on the magnitude of reactance and the
effect of the equivalent parallel resistance (Rp) and equivalent series resistance
(Rs) on it.
Table E-2 Parallel/Series equivalent circuit models and measurement functions of the
E4981A
Circuit model
Parallel equivalent
circuit model
Series equivalent
circuit model
•
•
Figure E-6 Selection of capacitance measurement circuit model
Keysight E4981A 120 Hz/1 kHz/1 MHz Capacitance Meter
Measurement function of E4981A
Cp-D, Cp-Q, Cp-G, Cp-Rp
Cs-D, Cs-Q, Cs-Rs
When capacitance is small:
When capacitance is small, reactance is large. Therefore, the effect of Rp is
greater than that of Rs. When Rs is small, its effect can be neglected
compared to capacitive reactance. In this case, use the parallel equivalent
circuit model shown in
When capacitance is large:
When capacitance is large, reactance is small. Therefore, the effect of Rs is
greater than that of Rp. In this case, use the series equivalent circuit model
shown in Figure E-6 (b).
Table
Figure E-6 (a).
E-2. You must select one of
Definition of D, Q, G
D = 1/(|2ΠfCp|Rp)
Q = 1/D = |2ΠfCp|Rp
G = 1/Rp
D = |2ΠfCs|Rs
Q = 1/D = 1/(|2ΠfCs|Rs)
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