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just DQ control for minimum meter indication, The
ai the unknown capacitor is read from the D scale
P3tieated by the red pointer in the DQ window.
8-34. The fastest procedure for C measurements is
-8в follows:
а, Set FUNCTION
switch to Cp AUTO position.
b. Connect capacitor to unknown terminals.
с. Turn the CRL control cw to 1080,
d, Rotate RANGE
switch until à crossover point of
` the indicator Lights is obtained.
(Left indicator lights
instead of right one and vice versa.)
I you cannot
obtain à crossover,
see step e note.
e, If left indicator lights, adjust SENSITIVITY con-
"trol for а right deflection of the null meter pointer.
H the right indicator lights, turn RANGE switch one
step cew and adjust SENSITIVITY control for a right
deflection of the null meter pointer.
Note:
if the
right indicator
stays lit regardless
of the
RANGE
switch position,
the unknown
value of the capacitor
must be beyond the highest
range оі the bridge (>
1000 ий.
ЕЁ the left indicator stays lit regardless ої
the RANGE
switch position, the unknown value of the
eapacitor must be below 1000 pF.
.
1, Rotate the CRL control cew until a crossover of
; the indicator lights is obtained.
` g. Set SENSITIVITY full cw and adjust for null with
CRL control.
h, Read final capacitor
value on the CRL counter
and units display.
4-25.
VOLTAGE ACROSS UNKNOWN C.
3-26,
When
voltage across
the unknown
C is to be
measured,
a vacuum
tube voltmeter
such as an HP
4000, 400H, or 400L should be used.
The procedure
18 ав follows:
а. Make the capacitance measurement
as outlined
Ал Paragraph 3-23, апа leave the instrument set up at
null
b. Isolate the Voltmeter from power line ground by
using а two-prong power cord adapter and leaving the
adapter pigtail lead disconnected from ground.
. €. Connect the Voltmeter input ground terminal to
the 4260A rear panel detector ground terminal.
d, Connect the other voltmeter input terminal tothe
4260A UNKNOWN
terminal
(not the LOW terminal).
Read the voltage acrossthe unknown C onthe voltmeter.
3-21.
INFLUENCE
OF D IN Cp AUTO
MENT.
8-28,
The accuracy
that is specified for Cp AUTO
measurement is obtained when D is less thani,
When
D is greater than 1, accuracy of Cp AUTO measure-
02337-1
Section III
Paragraphs 3-24 to 3-35
ment
is reduced
due to the reactance of the variable
resistance
circuit of the AUTO null.
Typical data is
ghown 1n Figure 3-2,
1
ALLOWARLE
ERROR (SPECIFIED)
j
EXPECTED ERROR {МОТ SPECIFIED)
j
TYPICAL
| | |
|
+ м
š
к
guo
@
u
J
o
1
m
в
№
29
.50
10
20
50
I
с
50
20
10
05
ог
Figure 3-2,
Capacitance and Inductance
Errors in AUTO vs
D& Q
3-29. INDUCTANCE
MEASUREMENTS.
3-30.
INTRODUCTION,
3-31.
Inductance
measurements
are normally made
at frequency of 1kHz fromthe internaloscillator.
For
L measurements
at frequencies between 20 Hz and 20
kHz, an external oscillator can be connected, as out-
lined in Paragraph 3-42, Special Measurements,
Di-
rection lights indicate the correct rotation direction
юг Ls AUTO measurements.
The measured L value
is displayed on the CRL counter with correct decimal
point location,
units,
and equivalent circuit also dis-
played.
Quality factor (Q) can be measured after the
bridge
is balanced
ior the inductance measurement.
The measured Q value is displayed on the DQ dial,
3-32.
RESIDUAL INDUCTANCE.,
3-33.
Residual inductance of the UNKNOWN terminals
can be measured
with heavy short wire connected to
these terminals,
ifs value is typically 1 uh or less.
When &mall inductance measurements
are made, this
residual
inductance
should
be subtracted
from the
measured value.
Ifexternal leads are used to connect
the unknown,
the residual inductance measurement
should include the lead inductance.
Errors caused by
residual and lead inductances are listed in Table 3-1.
3-34.
Ls AND Lp MEASUREMENT
DIFFERENCES,
3-35,
The measured
value of inductance depends on
whether a series or parallel equivalent circuit is used
for the measurement,
The
relationship between
a
series inductance (Ls) circuit and a parallel inductance
(Lp) circuit is as follows:
3-5
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