
116 Electrical impedance: principles, measurement, and applications
schematics to obtain a 4P bridge: Fig. 4.23 shows a milestone example given
by Cutkosky (1970).
Z
1
Z
2
Z
3
Z
4
D
L1
D
L3
D
L2
D
L4
D
H13
D
H24
Figure 4.23
Principle schematics of a 4P Wheatstone bridge. The six generators are
trimmed to null all six network detectors.
Adapted from Cutkosky (1970, Fig. 2).
Such a direct compensation scheme asks for highly sensitive detectors and
stable generators, since any drift from perfect null condition causes measure-
ment errors. In the past (Cutkosky, 1970), it has been considered only as a
didactical principle. The evolution of digital bridges, Ch. 5, however,