Specifications

5-16
5.3.4 Turns ratio (N)
Turns ratio (N) measurement technique, which can be used with general impedance measuring
instruments, approximates the turns ratio (N:1) by connecting a resistor to the secondary as shown
in Figure 5-23 (a). From the impedance value measured at the primary, the approximate turns ratio
can then be calculated. Direct turns ratio measurement can be made with a network analyzer or
built-in transformer measurement function (option) of the Agilent 4263B LCR meter. The turns ratio
can be determined from the voltage ratio measurements for the primary and the secondary, as
shown in Figure 5-23 (b). The voltmeter (V
2
) should have high input impedance to avoid affecting
the secondary voltage. The properties of magnetic core and the effects of stray capacitance limit the
applicable frequency range of the turns ratio measurement methods.
Figure 5-23. Turns ratio measurement
RZ
N1:
Z = N
2
R
N =
R
Z
(a) Approximation by measuring
impedance ratio
(b) Direct measurement by using voltage
ratio measurement
N1:
V
1
V
2
V
2
N =
V
1