voltage measurements. The switch within the
Capacitor
Exam-eter automatically connects the unit
under test
Into the proper circuits.
The leakage
test
section of the Instrument consists
of a variable source of D.C.
voltage
and a
meter. The
leakage Is read directly on a D.C. mllllammeter. A
leakage current
up to
50 mllllamperes can be measured
along with the actual D.C. voltage Impressed on the
capacitor. No
switching from
tap to
tap
is necessary
as a continuously variable D.C. voltage can be obtained
from 0 to 650 volts. This makes It possible to form
up
electrolytic capacitors of any rating up to 550 volts.
By special regulation of the leakage circuit the meter
when
set on the 50 ma. range is
protected
against
damage due to overloads caused by shorts and high
leakage electrolytlcs.
The megohm range
of
the instrument
Is particularly
useful
for the measurements of Insulation resistance on
paper and mica condensers. It
is
.especially useful
In
detecting
faulty coupling condensers. The instrument
provides
direct and positive means of making
measure-
ments
as
the meter
dial Is accurately calibrated In
megohms.
The
sensitivity of the instrument is high and will be
found useful for tests
on Insulating materials, and parts
such
as terminal boards.
The range
covered by this part of the instrument
Is
from 3 megohms
to 10,000 megohms in three separate
ranges.
The Puick-Check features
of the Solar Models QCA
and pc are
Incorporated in this Instrument. The pulck-
Check section consists essentially
of a
complex
balanced
radio frequency oscillator,
a visual indicator in the form
of a
sensitive mllllammeter, and a source of power. The
oscillator system Is arranged to permit easy
and
positive
determination
of capacity quality under static or dy-
namic
conditions. The condenser under test may be
operating in
a circuit, or it may be disconnected. The
Puick-Check section determines opens, Intermittents,
shorts,
R.F. impedance
and high power factor.
The
instructions to follow specify certain limits which
have
been set as
standards to be used as a guide
in
judging satisfactory
condensers. These limits were set
arbitrarily
on the basis of
our years of
experience with
condensers. In
general, condensers which meet these
specifications
will be found satisfactory
in operation,
while
those rejected will
interfere with satisfactory opera-
tion of the
circuit in which they are
used.
Pn
the
other hand,
it
is well known that
condensers
used in certain specific circuits
may be more or possibly
less critical with
respect to their electrical
constants than
our limits
indicate.
These exceptional cases can be
handled best by
intelligent
use of the
Capacitor Exam-
eter
after
careful and thorough study of all the ac-
companying instructions.
CAUTION: Do not remove or loosen
the bridge con-
trol
knob,
since this is carefully set during
calibra-
tion at the factory.
OPERATING
INSTRUCTIONS
PUANTITATIVE
MEASUREMENTS
In
order to make
quantitative measurements at
least
one terminal of the condenser
must be disconnected from
the circuit, or the condenser may be
entirely discon-
nected.
To
make the
instrument ready for test, the
following
procedure should be followed:
1. Insert the test leads,
with
the
rubber protection
over the clips, into the tip jacks marked "Cond.
Test." The red
plug
should be connected into the
red tip jack and the black plug
Into the black
tip jack to obtain the correct polarity.
2. Set the selector switch on the desired range.
3. Connect the line plug to the power outlet and
turn
on the voltage control
switch. Allow about
one minute for the tubes to heat up and then
proceed with the testing as described below.
INSULATION RESISTANCE TEST
A simplified circuit diagram showing
the
Insulation
resistance test
circuit
is given In Rg. I. This circuit con-
sists of a D.C. source of voltage,
a
vacuum tube volt-
meter, and a mllllammeter calibrated In megohms. A
leakage current flowing
through
the condenser under test
will develop a voltage across "Rc" which is Impressed
as a negative bias across
the
grid of the V.T.
causing
a decrease In the plate current. The change in plate
current caused by the leakage of the condenser
is shown
2
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