Philips PM 6302 - Measuring with External; Voltage Supply

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