ESI 250-DA - DC Capacitance Measurement Precautions

2.
4.
4.
2
THINGS TO WATCH
OUT
FOR (cont.
i)
where:
-
DC
voltage
across
the
unknown
capacitor
-
DC
voltage
at the
generator
terminals
-
DC resistance
of the
unknown
capacitor
-
Resistance
of the
range
resistor
DC
power can be
supplied
through
the
generator
terminals
by using
an
auxiliary
ac
generator
instead of the bridge generator.
This generator
must
be
isolated from
the dc
power supply by a capacitor of
at
least
(lO/fj^^) pf.
The
internal
bridge
generator
can
be used
as the
ac
source
by
making
the
special
connection
shown
below* Bring
out the
generator leads.
Connect
one
generator
lead
to
an
isolating capacitor.
Connect
the
other side
of
the
capacitor
to
the EXT
GEN
terminal
marked LO.
Connect the
second
generator
lead
to
the
other
EXT
GEN terminal.
Set
the generator
switch
to
EXT
GEN,
It
is
also
possible
to connect
the capacitor
inside the
bridge,
in
series with
the
generator lead. If this is done
no
external
leads are
needed, and the
generator switch is set
to
INTERNAL
AC.
In either
case,
the
capacitor
should
have a value of
at
least
M-f*
GENERATOR
TRANSFORMER
LEADS
IF INTERNAL
CAPACITOR
IS
TO BE
USED
CONNECT
IT
IN SERIES
WITH THIS
LEAD.
IF
THIS IS DONE
EXTERNAL
LEADS
ARE
NOT NEEDED.
If
this
operation is repeated
often
it
may be helpful
to
connect
two
binding
posts in
series
with one
transformer lead so
that
an external
capacitor
can
be
easily attached.
These can be
mounted
between the
generator
and
detector switches.
When
the capacitor is not
needed
the
terminals
can be
connected
by a shorting
bar.
TO EXT
GEN
HI
CONNECT
>
GENERATOR
LEADS
HERE
THROUGH
CAPACITOR
TO
EXT
GEN LO
(Msli
I
250-DA
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