Fluke 825A - Functional Description

CONTROLS
TERMINALS
AND
CIRCUIT
LOCATION
SYMBOL
FUNCTIONAL
DESCRIPTION
INDICATORS
NULL
switch
Front
panel
-
А
B,C,
D,
and
E
Front
panel
56,
87,
voltage readout S8, S9,
$10
Front panel
dials
a
Rear panel of
825A, front
panel of 825AR
Rear panel of R1
825A, front
panel of 825AR
га
Rear panel of
825A, front
panel of 825AR
Set to УТУМ for determining the approximate
value
of
unknown
voltage
prior
to
differential
measurements. Five null voltage ranges of 10, 1,
0.1, 0.01, and 0.001 volts are used for differ-
ential measurements. These ranges represent
full
scale
differences
between
the
unknown
voltage
and
the
amount
of
precision
internal
reference
vol-
tage
that
is
set
on
the
voltage
readout
dials.
Provide
an
in-
line
readout
of
the
amount
of
internal
reference
voltage
necessary
to
null
the
unknown
voltage.
Serve
as
decimal
points
for
the
voltage
readout
dials.
A
different
light
illuminates
for
each
position
of
the
RANGE
switch.
Decimal lights
Changes
polarity
of
825A
to
match
polarity
of
un-
known
voltage.
With
this
switch
in
the
positive
position,
the
polarity
of
the
upper
input
binding
post
is
positive
with
respect
to
the
lower
input
binding
post
(middle
post).
Polarity switch
Output
terminals
Provided
for
attaching
a
recorder
to
monitor
vol-
tage
excursions.
Output level
control
Varies
the
output
level
of
the
output
binding
post
from
0
to
approximately
20
millivolts
full
scale
deflection.
Indicates
approximate
voltage
when
825A
is
in
VTVM
mode
and
difference
between
unknown
and
internal
reference
voltage
when
825A
is in
differential
mode.
The
upper
scale,
500-0-500,
is used
when
the
NULL
switch
is
ве
to УТУМ.
At
all
other
times,
the
lower
scale,
1-0-1,
is
used.
Sets meter to zero mechanically. This adjustment
should be used only after instrument has been
turned off for at least three minutes or when the
meter terminals have been shorted.
Mechanical
zero control
Fuse holder protrudes from instrument to provide
easy access to the fuse.
Figure 2-1. CONTROLS, TERMINALS, AND INDICATORS. (Sheet 2 of 2)
2-2.
ZEROING
INSTRUCTIONS
a.
Mechanically
zero
the
meter
with
the
adjustment
screw on the front of the meter case. If the instrument
From
time
to
time,
it
may
be
necessary
to
adjust
the
in-
is
in
the
case,
it
must
be
shut
off
for
at
least
three
ternal
meter
zero
control.
This
will
normally
be
done
at
minutes
prior
to
this
adjustment.
If
out
of
case,
another
somewhat
more
frequent
intervals
than
complete
instru-
method
would
be
to
short
out
the
meter
terminals
prior
ment calibration. Proceed as follows: to zeroing.
2-2