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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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