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~ __ TY_P_E_l_60_8_-A_1M_P_E_D_A_N_C_E_B_R_I_D_G_E
_
C
s
= (I +D2)Cp;
1
C p = 1 +D2 C
s
D2
1
1
R
s
= - - R = 1 +Q2 R p
(1 +Q2)G p
1 +D2
p
R
p
1 +D2
(I+Q2)R
s
= - - R
D2
s
1
C
p
QG
p
G
p
=
(1 +Q2) R
s '
= - -
ev
lC
s
L S
R
p
C
p
R
p
L
p
G
p
R S
G
p
R S
evC
p
Q = - =
G
p
1 +
Q2
1
jwLpR p
R
p
+ jevL
p
Resistance and Inductance
z
1.4 SERIES AND PARALLEL PARAMETERS.
An impedance that is neither a pure reactance nor
a pure resistance can be represented at any specific fre-
quency by either a series or a parallel combination of re-
sistance and reactance. The values of resistance and re-
actance used in the equivalent circuit depend on whether
a series or parallel representation is used.
The equiv-
alent circuits are shown in Figure 1-4. A nomograph for
series-parallel conversion is given in Figure 1-7.
The
relationships between the various circuit elements are as
follows:
1
L p ; L p =
1
+Q2 L =
(1
+D2)L
1 +D2
Q2
s
s
Figure 1-4. Equivalent circuits lor
complex impedance.
1.5 ACCURACY OF MEASUREMENTS.
1.5.1
CGRL ACCURACY AT 1 KC.
The basic bridge
accuracy is 0.1%. This is a function of the accuracy of
the adjustment and stability of the bridge arms. The
in-
strument is initially calibrated to an accuracy of ±0.05%
or better and should hold the 0.1% accuracy for well
beyond the two-year warranty period.
A simple calibra-
tion check procedure is given in Section 5.2.
The
lowest-resistance (I-ohm) resistance ratio
arm is the most difficult ratio arm to set aCfurately, is
the most affected by switch and lead resistance, and
has slightly poorer stability than the other arms. There-
fore, the accuracy specification for the lowest imped-
ance range for each bridge is 0.2%.
The fixed error of ±0.005% of full scale or one-
half a digit on the counter read-out allows for backlash
in the adj ustment and for the limitations of linearity and
resolution of the vernier rheostat. This fixed error gives
an over-all accuracy at 1 kc (on all but the lowest range)
1 +D2
1
ev C p R p
Resistance and Capacitance
•
1
Z=R +-.-
S
J evC
s
4
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