Agilent Technologies 4294A Specifications download pdf (Page 80)

±0.001, the maximum measurable Q value is 90.9. See Appendix E for Q accuracy calculation equa-

tion.) Except for resonant method, the impedance measurement instrument calculates the Q value

by Q=X/R. Measured vector of the relatively high Q inductor is as shown in Figure 5-12. The imped-

ance measurement error is represented by a small circle enclosing the error vector (∆). The R value

of a high Q (low loss) inductor is very small relative to the X value. Small changes in R results in

large Q value changes (Q=X/R). Therefore, error in R measurement can cause significant error in Q,

especially in high Q devices.

The following methods deliver improvement to Q measurement accuracy:

(1) Employ the instrument with better accuracy.

(2) Perform optimum compensation for residual resistance.

(3) Utilize equivalent circuit analysis function and calculate Q value from the equivalent circuit

parameter values obtained for the DUT. Refer to paragraph 5-14 “Equivalent circuit analysis

function and its application” for details.

Figure 5-9. Inductor test signal current

Figure 5-10. Test fixture effects

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Agilent Technologies 4294A Specifications Page 80