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c. Set the function switch to !NT AC.
d.
Connect the unknown capacitor to the UN-
KNOWN terminals.
e. If the proper range setting of the FULL SCALE
RANGE is not known, set the concentric CGRL controls
for a reading somewhere near 5000, adjust the DET
SENS control for an upscale meter reading and set the
FULL SCALE RANGE switch for a minimum meter de-
flection.
f.
Adjust the concentric CGRL controls and the
DQ control for minimum meter deflection.
The DET
SENS control may have to be readjusted to give greater
sensitivity as balance is approached.
g.
The capacitance of the unknown is indicated
directly on the counter readout with the correct decimal
point and unit illuminated. The D of the unknown is in-
dicated directly on the illuminated scale on the DQ dial.
The meaning of an X indicator is explained in para-
graph 2.2.
2.4.1.2
Accuracy.
The accuracy of the C reading is
±O.I% 'of the reading ±0.005% of full scale (which is
±1/2 of the last digit) on all but the highest capacitance
range,
where the accuracy is
±0.2% of the reading
±0.005% of full scale. On the lowest C range it is nec-
essary to subtract the residual (" zero") capacitance of
the bridge terminals, approximately 0.25 pf, from the
r~ading
to determine the correct value of the unknown
capacitor. If external leads are used to connect the un-
known, this zero capacitance is increased and should be
subtracted from the reading. The error caused by capac-
itance between the terminals and leads may be removed
by means of a three-terminal shielded capacitance meas-
urement (refer to paragraph 3.2).
The residual resistance and inductance of the
bridge have negligible effect on the C or D accuracy
except for a slight D error on the highest C range (D
error
=
0.006 when C x
=
1000 pf).
However, if long
leads are used when measurements are made on large
capacitors, a correction for the lead resistance and in-
ductance may be necessary.
The correction terms are
given in Table 2-5.
When capacitors with high 0' s are measured, an
additional error of ±(0.5%) D2 is added to the specifica-
tion (refer to paragraph 1. 5. 3).
This error is negligible
when D is less than 0.2.
2.4.2 l-KC INDUCTANCE MEASUREMENT.
2.4.2.1
Procedure.
a. Set the GEN LEV control fully clockwise.
OPERATING PROCEDURE
Note:
For some iron-cored inductors the induc-
tance measured will depend upon the excitation level
(refer to paragraph 2.4.5.4).
b. Set the BRIDGE SELECTOR to:
Ls - if the series inductance is desired and Q is be-
tween 0.5 and 5"0.
Lp - if the parallel inductance is desired and Q is greater
than 1.
(Note: Ls
=
Lp within 1% if
Q
)32)
R s - if Q is less than 0.5 (measure R s and Q;
L s
=
QRs refer to paragraph 2.4.3).
cu
c. Set the function switch to INT AC.
d. Connect the inductor to be measured to the UN-
KNOWN terminals.
e. If the proper range setting of the FULL SCALE
RANGE is not known, set the concentric CGRL controls
for a reading somewhere near 5000, adjust the DET
SENS control for an upscale reading, and set the FULL
SCALE RANGE switch for a minimum meter deflection.
f.
Adjust the concentric CGRL controls and the
OQ control for minimum meter deflection.
The DET
SENS control may have to be readjusted to give greater
sensitivity as balance is approached.
g.
The inductance of the unknown is indicated
directly on the counter readout with the correct decimal
point and unit illuminated. The Q of the unknown is in-
dicated directly on the illuminated scale of the OQ dial.
The meaning of an X indicator is explained in paragraph
2.2.
2.4.2.2
Accuracy.
The accuracy of the L reading is
±O.I% of the reading ±0.005% of full scale (which is
±1/2 of the last digit) on all but the lowest ranges,
where the accuracy is ±0.2% of the reading ±0.005% of
full scale.
When Q is low there is an additional error
of 0.5%
d2'
which is negligible when Q is approximately
5 or higher.
On the lowest range, the residual inductance of
the binding posts (0.14 /-ih) must be subtracted from the
reading in order to obtain full accuracy.
If external
leads are used to connect the unknown inductor
to
the
bridge, then the residual inductance should be measured
and subtracted from the L reading. To measure this lead
inductance, short the leads together, measure the imped-
ance on the R s bridge, and calculate L s
=
~s.
Be
careful
to
keep the lead configuration the same for the
residual inductance measurement and the total induc-
tance measurement, since an increase in the area be-
tween the leads would increase the residual inductance.
13
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