HP 4284A - Page 174

Parallel/Series
Circuit Mode
To measure L, C, or R, there are two equivalent circuit mo dels, the
parallel and series mo des as shown in Table 6-1, and the HP 4284A
can select the mo de by setting the FUNC (C
p
,C
s
,L
p
or L
s
) on the
MEAS SETUP page. To determine which mo de is b est, consider the
relative imp edance magnitude of the reactance and R
s
and R
p
.
Table 6-1. Parallel/Series Circuit Mode
Circuit Mo de Measurement
Function
Denition of D, Q and G
C
p
mo de C
p
-D
C
p
-Q
C
p
-G
C
p
-R
p
D=
1
2  fC
p
R
p
=
1
Q
G=
1
R
p
C
s
mo de C
s
-D
C
s
-Q
C
s
-R
s
D=2  fC
s
R
s
=
1
Q
L
p
mo de L
p
-D
L
p
-Q
L
p
-G
L
p
-R
p
Q=
R
p
2  fL
p
=
1
D
G=
1
R
p
L
s
mo de L
s
-D
L
s
-Q
L
s
-R
s
Q=
2  fL
s
R
s
=
1
D
Selecting Circuit Mode
of Capacitance
The following description gives some practical guide lines for selecting
the capacitance measurement circuit mo de.
Small Capacitance (modeled by (a) in Figure 6-3)
Small capacitance yields large reactance, which implies that the eect
of the parallel resistance (R
p
) has relatively more signicance than
that of series resistance (R
s
). The lowvalue of resistance represented
byR
s
has negligible signicance compared with the capacitive
reactance, so the parallel circuit mode (C
p
-D or C
p
-G) should be
used.
Large Capacitance (modeled by (b) in Figure 6-3)
When the converse is true and the measurementinvolves a large
value of capacitance (low imp edance), R
s
has relatively more
signicance than R
p
, so the series circuit mo de (C
s
-D or C
s
-Q)
should b e used.
Measurement Procedure and Examples 6-5