12
2.2.3. 1. Searching the correct measuring
range in case
of
unknown
capacitance value
—
Depress push-button "SEARCH"
—
Switch
over the measuring ranges
—
The correct measuring range is found when the indicator
points
to the "WV"-field
—
Pointer deflection
too small
—*
select a lower measuring
range
—
Pointer
deflection too large
—
*•
select a higher measuring
range.
2.2. 3. 2. Measuring
the
capacitance
and
the loss factor D in case of
a
known
measuring range
—
With the vernier adjust the pointer deflection to a minimum.
—
With potentiometer
"Q/D" adjust the
loss factor D so that a better minimum is obtained
—
Repeat this
two adjustments
alternately for the lowest minimum
—
If
no
clear
minimum can be reached,
depress push-button "D" (D < 1.4;
measuring frequency 100 Hz) and
repeat
the
procedure
above.
—
Multiply
the
scale
reading by
the value selected with the range
selector
to
obtain the exact capacitance
value.
—
To
obtain the loss factor D
=
tag 6
read the value adjusted with
potentiometer "Q/D" and
multiply it by
0.01 or 0.1 depending on the position of push-button "D"
—
When measuring smaller capacitances substract
the initial capacitance of this
instrument from the measured
value. The initial capacitance can
be measured, when no sample is
connected to sockets "l-E".
Note: If, when measuring smaller
capacitances,
no
correct minimum can be
adjusted, eventually
screen
the
sample for
external mains stray fields.
2.23.3.
Measuring capacitances with formation voltage
A
In order to
form electrolytic capacitors and in case
of capacitance
measurements with d.c. bias voltage
for the
sample, a mains-independent battery can
be connected to
sockets "DC-BI AS" at the rear. The
short-circuit
plug must
then be removed.
Pay attention for the polarity
of
the
sample:
"+"
—
*
"I";
"
»
"E"
The a.c. internal resistance
of the battery must be
low; i.e. under
certain circumstances a
capacitor
C
p
must be
connected in parallel with the battery;
the value of C
p
should
be higher than or
equal
to
the sample
capacitance;
but
it
must
be at least lOOpF (see
Fig.
5).
In order to protect the
measuring bridge, the d.c.
current from the battery must
be limited by a resistor
Rv.
The resistance
must be
at least 50 Q
per volt of the
supplied d.c. voltage (see
Fig.
5).
For measuring the capacitance and
the loss factor
of the sample see 2.2.3. 1.
and 2.2.3.2.
2.2.34. Measuringjunction
capacitances
In
order
to
measure
the
junction
capacitance of a varicap,
proceed as
follows:
-
Supply
an adjustable
d.c.
voltage from a
mains-independent
galvanic battery and
connect an external
a.c.
voltage source to the
bridge supply
conform
to
figure 6.
—
Connect
the sample with the
cathode to
terminal I and the
anode
to
terminal E.
By
stepwise changing the
d.c.
voltage
and measuring the
capacitance
of the varicap in accordance
with
2.2.3.I.
and
2. 2.3.
2.,
the
characteristic
of the
sample can
be
determined.
Note: The voltage of the
external bridge
supply should not be
higher than 1 V,
in order
to
avoid faulty
measurement by
overloading the sample.
2.2.4.
Measuring
inductances
—
Depress push-button "L"
—
Connect the sample to sockets
"l-E"
2.2.4. 1. Searching the correct
measuring range
in case of
unknown inductance
value
—
Depress
push-button
"SEARCH"
—
Switch over the
measuring
ranges
—
The correct
measuring range is found when the
indicator points
to
the "WV"fie!d.
—
Pointer deflection too small
*
select a
lower measuring range
—
Pointer deflection too
large
*
select
a
higher
measuring
range
—
For inductances with smaller
Q
«
1)
the searching procedure
can indicate
a
range which
is one decade too
low.
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