Series Capacitance Comparison Bridge
R1
Most common Capacitance bridge
circuit. Usually R3 and R1 are variable
so that bridge reads capacitance and D
R2
D
C3
Rx
R3
R1
R2
D
L3
Lx
R3
Scherring Bridge
Maxwell-Wien Bridge
Most common inductance bridge.
R2
R1
D
Cx
C3
Rx = R3
R2
R1
Lx = L3
R2
R1
Q=
ω L3
R3
Rx = R2
C1
C3
Cx = R3
R1
R2
D = ω R1C1
R2 R3
R1
Lx = R2 R3C1
D
Q = ω R1C1
Lx
R3
Rx
R1
Rx ≈ ω 2C12 R1 R2 R3
R2
C1
Lx ≈ R2 R3C1
for Q > 10
D
Lx
R3
Wien Bridge
Useful for determine frequency of a
voltage source
D = ω R3C3
Rx =
R2
C1
Useful for parallel inductance
measurements or high-Q measurements
where R3 of Maxwell bridge would have
to be impractically high. Also used for
measurements with dc current bias
because all current applied across
bridge flows in Lx
R1
R2
Rx
R1
Hay Bridge
Cx = C3
Rx
C1
Used in high-voltage bridges with a
high voltage capacitor as C3. Used in
high-frequency bridges because variable
capacitors can be used for both
adjustments. Use in dielectric
measurements because C1 gives highresolution loss measurement.
R2
R1
Cx
Series Inductance Comparison Bridge
Basic inductance comparison bridge .
Additional resistance added to inductor
with lower Q to get resistance balance.
Rx = R3
Rx
R1
R2
C1
f =
D
R3
C3
R2 R1 C3
=
+
R4 R3 C1
Rx
1
2π C1C3 R1 R3