LCX_UserManual_en_08_1.pdf - 第67页
Performing measurements R&S ® LCX Series 67 User Manual 1 179.2260.02 ─ 08 4. T o measure the parameters of a transformer coil: open secondary primary Figure 7-1: Primary inductance measurement a) Connect the "C…
Performing measurements
R&S
®
LCX Series
66User Manual 1179.2260.02 ─ 08
6. To achieve the expected result, set the frequency to 50 Hz.
The expected value is approximately 1000 µF ± tolerance. The dissipation factor
"D" is low, even close to 0, and the phase angle is ≈ -87°.
Decreasing the frequency reduces the loss angle, and thus the real components
come closer to the ideal value.
Measuring an inductor
This example refers to a measurement of an inductor of 280 µH on a printed circuit
board, by using the miniature SMD tweezers (R&S LCX-Z4), see Section 6.1.4, "Test
tweezers for SMD components", on page 56.
1. To select the inductance measurement (DUT component type), press the [L] key.
2. Set the measurement frequency of the test signal, e.g., 500 kHz.
3. To select the parameters for measurement results display:
a) Select the measurement pair softkey in the upper left corner, to open the selec-
tion editor.
b) Select the parameters "Ls-Q" (serial inductance, quality factor).
c) Repeat the steps to select the second parameters, e.g. select "Z-Θ" (impe-
dance, phase angle).
4. Carefully contact the miniature tweezers of the test fixture to the sample inductor
on the circuit board.
5. Hold the tweezers closed during measurement.
The measurement starts and you can see the readings on the screen.
The expected result is approximately "Ls ≈ 280 µH" ± tolerance. The phase angle
"Z-Θ"≈ +70°.
Measuring the primary or secondary inductance of a transformer
This example refers to a measurement of a transformer with the test fixture (R&S LCX-
Z5), see Section 6.1.5, "Test fixture with cables for transformer components",
on page 57.
A transformer measurement often leads to varying measurement results due to iron
core losses and to the unknown state of the premagnetized core. The sample compo-
nent depends on both, the frequency and the measurement voltage. Varying the fre-
quency causes changes in magnetization and iron core losses, which impact the phase
angle, and an increasing measurement voltage leads to higher impedance.
This measurement on the transformer, also considered as "open" measurement, corre-
sponds to the measurement of a single coil.
To measure the primary or secondary inductance:
1. For inductance measurements, press the [L] key.
2. Set the measurement frequency, e.g. the mains frequency for a mains transformer.
3. Select the parameters for measurement results display as described under "Mea-
suring an inductor" on page 66.
Performing measurements
R&S
®
LCX Series
67User Manual 1179.2260.02 ─ 08
4. To measure the parameters of a transformer coil:
open
secondaryprimary
Figure 7-1: Primary inductance measurement
a) Connect the "Common" test leads of the corresponding circuit to one terminal
of the transformer winding to be measured.
b) Connect both, the "1" and the "N" test leads to the other terminal of the winding
to be measured.
c) Leave the second winding of the transformer open.
To measure the secondary inductance of the transformer, connect the secondary
winding to the R&S LCX-Z5 and leave the primary winding open.
Measuring the transformer ratio and the mutual inductance of a transformer
This example refers to a measurement of a transformer with the test fixture (R&S LCX-
Z5).
To measure the mutual inductance, both windings are connected to the test fixture.
1. Press the [Transformer] key.
2. Set the measurement frequency, e.g. the mains frequency for a mains transformer.
3. Select the parameters for measurement results display:
a) Select the measurement pair softkey in the upper left corner, to open the selec-
tion editor.
b) Select the parameters "N-ΘNd" (transformer ratio, phase angle).
c) Repeat the steps to select the second parameters, e.g. select "M-ΘNd" (induc-
tance, phase angle).
4. To measure the parameters of a transformer circuit:
a) Connect both, the "1" and the "Common" test leads of the test fixture to the pri-
mary winding of the transformer.
Performing measurements
R&S
®
LCX Series
68User Manual 1179.2260.02 ─ 08
b) Connect both, the "N" and the "Common" test leads to the secondary circuit of
the transformer. Observe the polarity of the windings, if known. Both "Common"
test leads are equivalent.
The measurement starts and you can see the readings on the screen.
The transformer ratio "N-ΘNd" is the ratio between measured primary voltage and
measured secondary voltage.
The mutual inductance "M-ΘNd" is calculated from measured primary current "I
p
"
and the measured secondary voltage "V
s
" as follows (Z is a virtual complex impe-
dance value):
Z
= virtual impedance
V
s
= measured voltage in secondary circuit
I
p
= measured current in primary circuit
M = mutual inductance
Im{Z} = imaginary part of impedance
ω
= angular frequency
If ΘNd is between 90° and 270°, the transformer inverts the signal. In this case, the
"M" result can display "RANGE" instead of a value. Invert the connection of one of
the windings to obtain a non-inverting setup and a valid measurement result
for "M".
Measuring the leakage inductance of a transformer
This example refers to a measurement of a transformer with the test fixture (R&S LCX-
Z5). You can also use only the included standard cables for inductance measurements
without the test adapter.
The connections and measurement settings are the same as for primary inductance
measurement, except that the secondary winding is shorted.
1. To select the inductance measurement (DUT component type), press the [L] key.
2. Set the measurement frequency, e.g. the mains frequency for a mains transformer.
3. Select the parameters for measurement results display as described under "Mea-
suring an inductor" on page 66.
4. Short-circuit the secondary winding of the transformer.