Model 4342A
Section III
Paragraphs 3-73 to 3-75
Series Connection Measurements
3-73. SERIES
MEASUREMENTS.
C.
Note
Short-circuit the unknown (series con-
nection terminals) with a heavy (low
impedance) shorting strap.
In the following series connection
measurement procedures, set 43424
Q RANGE as appropriate unless
specifically instructed otherwise.
3-74.
Low Inductance Measurement.
3-75. Measurement of small inductors at
relatively low frequencies can not be made
directly at the measurement COIL terminals.
However, by using an external high Q capaci-
tor (such as the 16462A Auxiliary Capacitor)
connected in parallel with the tuning capa-
citor, resonance can be obtained at the de-
sired frequency. A second method, which is
explained here, is the series method.
This
method is recommended for measuring low value
inductors without using an external capacitor
(but with an external inductor).
When the measuring circuit is resonated using
a reference inductor, the test inductor
placed in series with the reference inductor
will lower the tuning frequency.
To restore
resonance at the measurement frequency, the
tuning capacitance must be reduced.
The in-
ductance of the unknown inductor can be
determined from the relationship between the
tuning capacitances at the same frequency.
After the sample is connected, quality factor
and equivalent series resistance can also be
calculated from a reduction of panel Q meter
indication. Proceed as follows:
a. Depress the appropriate FREQUENCY
RANGE button and set FREQUENCY dial
control for the desired measurement
frequency.
b. Select a reference inductor which
allows the measuring circuit to reso-
nate with a tuning capacitance of ap-
proximately 400pF.
Connect unknown
inductor in series with the reference
inductor (between measurement LO
terminal and low potential end of the
reference inductor) and to measurement
COIL (HI and LO) terminals.
Note
If 16014A Series Loss Test Adapter
is available, attach it to measure-
ment COIL terminals.
Connect the
reference inductor to appropriate
terminals of the 16014A and unknown
inductor to 16014A series connection
terminals.
d. Adjust L/C dial and AC dial controls
for a maximum Q meter deflection.
Note sum of the C dial and AC dial
readings as Cl and panel meter read-
ing as Ql.
e.
Depress AQ button and adjust AQ ZERO
(COARSE and FINE) controls so that
meter pointer indicates zero (full
scale) on AQ scale.
Note
Press AQ button to release AQ func-
tion and recheck for correct reso-
nance. Again depress the AQ button
and recheck for hQ zero indication.
f.
Disconnect the shorting strap. Again
resonate the measuring circuit by ad-
justing L/C dial and AC dial controls.
Note sum of the C dial and AC dial
readings as C2 and panel Q meter AQ
reading. If meter pointer scales out
at the left end of the scale (AQ full
scale), reset the function to normal
Q measurement. The difference in Q is
calculated from the two Q values as
AQ
=
Q1
-
Q2.
Note
This procedure (steps c, d and f)
permits the unknown component to
be physically connected even
through it is electrically out of
the circuit, and eliminates pos-
sible errors by maintaining the
relative positions of the refer-
ence inductor and unknown component.
g.
Inductance of the unknown inductor is:
l,s = (zic;cf2)
(H) . . . . . (eq. 3-35)
Where,
W = 2~ times
the measurement
frequency.
Q value of the unknown is:
Q=
Q1Q2CC1
-
C2)
Cl (21
- C2Q2
"....... (eq. 3-36)
Where,
42 = Ql - AQ
Equivalent series resistance is:
Rs = ($$I Q1 - 42 (n)
. . . . . (eq.
3-37)
~CI QI Qz
3-23
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