3-5
In most
cases
the user
will
be
interested
in
the dominating
component of the CUT, displayed
in
the
RCL AUTO mode,
if
any other
parameter
shall
be displayed
the user may select
it
from the
front
panel menu
by activating
the
stepping
key
V
or
A
.
The
RCL meter
primarily determines
the
series reactance and resistance
of the CUT. From
these two
quantities
the selected
CUT
parameter is
calculated. The algorithm
used by the instrument including
series/parallel
and
parallel/series
transformation
formulas
and phasor
diagrams of the various
CUT
types
are presented
in
Appendix 1.
3.4.5. Special user
instructions
As
pointed out in
the
preceding
chapter in RCL AUTO
mode the instrument identifies the dominant
component of the CUT
and
display it. It
must be
considered that the decision,
if
the reactive
or
the
ohmic
component is
dominating,
generally depends on the
frequency.
In PM 6303 an 1 kHz test fre-
quency is applied.
This must
be taken into
account
especially if low-ohmic inductors
and
capacitors
or
high-ohmic resistors
are measured:
Lossy inductors:
When testing
small lossy
inductances often the series loss resistance is identified as
dominant
component and
displayed, because
at 1 kHz the
series reactance will
be
very low. Hence,
for Ls or Lp display
this parameter
must be selected
from the front-panel menu.
Lossy capacitors with high
capacitance, e.g.
electrolytic capacitors:
When testing capacitors the
user normally
will be interested in the
value of
the capacitance. As the
reactance of large
capacitors is very low, the
series
resistance can be dominant resulting in
Q
< 1 and
indication
of
Rp.
Hence, for Cs or Cp
display these
parameters must be selected..
Small capacitances
measured
with
the SMD
test fixture
PM 9542 SMD:
When testing very small
capacitances up to
some pF with PM
9542 SMD, the
alteration
of
the
zero
-
capacitance
depending on the contact
opening must
be taken into account, see Fig. 36a. For accurate
measurements in that range
the
adjustment of the zero
-capacitance should be done at contact opening
corresponding
to
the length of the
component to be
measured; for all normal measurements the adjust-
ment should be done at max.
contact opening.
High-ohmic
resistors:
When testing
resistors
in the
higher Mf2
range the
reactance of the parasitic
parallel
capacitance may
be lower
than the
resistance,
resulting
in a Cp
display. For indication
of
Rs
or Rp
these
parameters must be
selected.
Additional user
instructions:
In the Cs (2
V BIAS)
mode
capacitors can be
tested
with 2 Vdc
bias voltage.
For large
capacitors some
time is
needed
for stable
display
due
to
the charging
process
(approx.
0.5 s/mF).
For
the
parameter Cs
(2
V
BIAS)
overrange is
indicated
for Q
<
0.1
or if an
inductance is
identified.
The
resonant
frequency of
a larger
inductance
paralleled by
a parasitic
capacitance
can be
below
the
test
frequency. Then, of
course,
the CUT
represents a
capacitance at
1 kHz
which is
displayed.
When testing
large
inductors especially
in the kH
range
relative
small
parasitic
parallel
capacitances
will
effect
the measurement
result.
Thus
special
attention shall
be paid
on
careful Co
compensation.
When
testing
inductors with
ferromagnetic
cores
normally
due to
saturation
effects
the
inductance
will decrease
with higher
current or
voltage
amplitudes. At
PM
6303
these
amplitudes
are
resulting
from the 2
Vrms
open-circuit
voltage and
the
internal
400
fi
resistance
of
the
instrument and
the
CUT
impedance.
For lower
amplitudes
an
additional
resistor
3*
71.5
Q. may
be
connected
between
GUARD
and the
centre 4
mm socket
(marked
with
a
-sign).
For Rp
=
71.5 ft
fig.
6
shows the
CUT
voltage and
current versus
impedance
relationship.
In
the
shown
impedance
range the
measurement
error is
increased
to
about 0.5 %
maximum
by
the
load
resistor.
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