Specifications

4-4. Measurement cable extension induced error
Extending a 4TP measurement cable from the instrument will cause a magnitude error and phase
shift of the measurement signal according to the extension cable length and measurement frequen-
cy.
The following two problems will arise from the cable extension:
(1) Error in impedance measurement result
(2) Bridge unbalanced
The measurement error is mainly caused by the cable connected to the Hp and Lc terminals, and it
can be compensated by the instrument if the cable length and propagation constants of the cable are
known (refer to Figure 4-10). Bridge unbalance is caused by the phase shift in the feedback loop
that includes the Rr, amplifier, and the Lp and Lc cables. This can be compensated by an intentional
phase shift in the feedback loop. These two problems are critical only at frequencies higher than 100
kHz, and Agilent’s impedance measurement instruments can compensate for Agilent-supplied test
cables. In the frequency region lower than 100 kHz, the capacitance of the cable will only degrade
the measurement accuracy (but does not affect the bridge balance). This effect of cable extension is
shown in Figure 4-11.
Note: Cable length and electrical length are different and should not be confused.
Figure 4-10. Cable length compensation
4-9