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13
2.2.4.
2.
Measuring
the
inductance
and
die quality
factor
Q
in
the case
of
a
known
measuring
range
—
With
the vernier adjust the pointer deflection
to
a
minimum.
—
With potentiometer
"Q/D"
adjust the quality
factor
Q
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
"Q"
(Q
<
14)
and
repeat the
procedure
above.
—
When
measuring
inductances with smaller
Q
{<
1)
various
minima
can
be
found by
adjustment.
The
correct
measuring
value
is
obtained
at that
minimum
for
which
the pointer deflection
is
the
smallest.
—
To
obtain the exact inductance, multiply
the
scale
reading
by
the value selected with the range selector
—
To
obtain the
quality factor
Q:
^
When
push-button
Q
is
not
depressed, the
Q
is
the reciprocal
of the
loss
factor;
Q
=
—
.
Read
the
loss
factor
D
on
potentiometer
"Q/D"
and
multiply
by
0.01.
When
push-button
Q
is
depressed, the
Q
can be
read directly
on potentiometer
"Q/D".
Note:
When
measuring very
high inductances
{
100
H
-
1000
H)
the
natural
resonance frequency
can be
in
the range
of
the
measuring frequency of
the
bridge, in
this
case the
measuring
result
can
be
considerably
falsed.
Remedy:
If
the
natural
resonance frequency
of the inductance
can be
obtained, the
measuring
result
can be
corrected
using the following equation.
Lx
Lm
fo
2
~
fM
2
fo
2
L
x
"
unknown
inductance
Lm
" inductance
measured
with
the bridge
f
0
=
natural
resonance frequency
of the
coil
f|yi
= measuring frequency
of the bridge
(internal
1
kHz
or
external
100 Hz
-
20 kHz)
2.2.5.
Measuring with
external
a.c.
voltage
supply
If
capacitances or inductances
are to
be
measured
for
measuring frequencies
different
than
internal,
an
external
sine-wave generator can be
connected
to sockets
"Ext-AC"
at
the
rear of
the instrument.
The
lower frequency
limit
of
100
Hz
should not be passed because operating the instrument
at
frequencies
<
100
Hz
could cause
defects.
For
frequencies higher
than
20
kHz
the bridge
sensitivity
and
thus the
measuring accuracy
decrease.
The
scales
for
measuring
the
loss
factor
D
and
quality factor
Q
only apply
for internal
measuring
frequencies.
For
finding these
factors at
other measuring frequencies the following formulas can be
used.
—
For capacitance
measurement:
Push-button
"D"
not
depressed
f
M
Push-button
"D"
depressed
DfM
=
DiqOHz
100 Hz
—
For inductance
measurement:
Push-button
"Q"
not depressed
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