Agilent Technologies 4294A Specifications download pdf (Page 81)

Figure 5-11. Q measurement accuracy

Figure 5-12. Q measurement error

Furthermore, the following phenomena may occur when a cored inductor is measured using an auto

balancing bridge type instrument.

When a high level test signal is applied to an inductor, measurement may be impossible for a certain fre-

quency range. This is because of the nonlinearity of the core material which causes harmonic dis-

tortion of the test signal current. If the test signal level is high, an excessive distortion signal will

flow into the Lpot terminal of the instrument causing an unbalance or UNCAL condition (Figure 5-

13 (a)). To reduce the effects caused by core material nonlinearity, decrease the test signal level,

and if the measurement frequency is fixed, connect a LPF at the Lpot terminal as shown in Figure 5-

13 (b).

When a test cable is used to measure low-value inductors, measurement may be impossible for certain val-

ues of inductance at higher frequencies. This is caused by resonance resulting from the test cable

capacitance at the Hp and Hc terminals and the DUT’s inductance. In this case, the capacitance of

the cables should be changed so that the resonant frequency shifts to a much higher frequency than

the highest test frequency to be used. Reduce the length of the Hc and Hp cables or use another type

of cable to decrease the capacitance.

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Agilent Technologies 4294A Specifications Page 81