Section III
Paragraphs 3-76 to 3-79
Series Connection Measurements
Model 4342A
3-76. High Capacitance Measurement (145OpF).
3-77.
When the measuring circuit is reso-
ated using a reference inductor, a test capa-
citor placed in series with the reference
inductor will raise the tuning frequency.
To
restore
resonance
at
the measurement fre-
quency, the tuning capacitance must be in-
creased. The capacitance of the unknown 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 be cal-
culated from a reduction of panel Q meter in-
dication.
To measure a capacitance sample, proceed as
follows:
a. Depress the appropriate FREQUENCY
RANGE button and set FREQUENCY dial
control for desired measurement
frequency.
b.
Select a reference inductor which
allows the measuring circuit to reso-
nate with a tuning capacitance of
approximately 200pF.
Note
If the sample value is higher
than about 3600pF, it is recom-
mended that the initial tuning
capacitance setting be in the
vicinity of 400pF to obtain
better measurement accuracy.
Connect unknown capacitor in series
with the reference inductor (between
measurement LO terminal and low poten-
tial 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
capacitor to 16014A series connec-
tion terminals.
c. Short-circuit the unknown (series con-
nection terminals) with a heavy (low
impedance) shorting strap.
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 C1 and panel meter reading
as
QI.
3-24
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 AQ zero indication.
f.
Disconnct 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 Cz and panel meter indi-
cation as 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 = Qr - 42.
Note
This procedure (steps c, d and f)
permits the unknown component to be
physically connected even through
it is electrically out of the cir-
cuit,
and eliminates possible
errors by maintaining the rela-
tive positions of the reference
inductor and unknown component.
g-
The capacitance of the unknown capa-
citor is:
ClC2
cs = (C, - C,)
. . . . . . . . . .
(eq. 3-38)
Q value of the unknown is:
Q=
QlQ2(Cl -
C21
CIQI - CzQz
. . . . . .
(eq. 3-39)
Where, 42 = Q1 - AQ
Equivalent series resistance is:
Rs =
Q2 - (21 Q1 (52) . . (eq. 3-40)
WCIQIQP
Where, w = 271 times the measurement
frequency.
3-78.
Self-resonant Frequency Measurement
of High Capacitors.
3-79.
Capacitors have a residual inductance
which is dependent on the capacitor lead
To Next Page
Loading...
Need help?
General
