Specifications

2-2. Operating theory of practical instruments
The operating theory and key functions of the auto balancing bridge instrument are discussed in the
paragraphs 2-3 through 2-4-8. A discussion of the RF I-V instrument is described in paragraphs 2-5
through 2-7-6.
2-3. Theory of auto balancing bridge method
The auto balancing bridge method is commonly used in modern LF impedance measurement instru-
ments. Its operational frequency range has been extended up to 110 MHz. A detailed discussion of
the operating theory of a practical instrument using Agilent 4294A precision impedance analyzer as
an example will now be discussed. Table 2-2 lists the 4294A’s key specifications, and Figure 2-2
shows the simplified block diagram of the 4294A analog section.
Table 2-2. Agilent 4294A precision impedance analyzer key specifications
Figure 2-2. Simplified analog-section block diagram for the Agilent 4294A precision
impedance analyzer
2-5
Test signal Frequency: 40 Hz to 110 MHz, 1 mHz resolution
Signal level: 5 mV to 1 V rms
Impedance measurement |Z|, |Y|, θ, R, X, G, B, L, C, D, Q
parameters
Impedance measurement 3 mΩ to 500 MΩ
range
Basic measurement 0.08% of reading
accuracy
Display Color graphic display, 6 digits
DC bias 0 V to ±40 V, 0 mA to ±100 mA