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845AR
1-1.
INTRODUCTION
1-2.
The
Fluke
Model 845AR
High
Impedance
Volt-
meter-Null
Detector allows
measurement
of
dc voltages
from
one microvolt
to
1000
volts
dc
in
19
ranges.
When
used
as
a
null
detector
on
the
100
millivolt
range and
below,
the input
impedance
is
an
excellent
lj/
megohms?
A
linear
recorder
output allows the
instrument
to
be
used
for
production
testing,
and
also as a dc
amplifier
with
a
maximum
gain
of
120
db.
1-3.
The
instrument
may
be
wired
to
operate
from
a
line
power
source
of
115
volts
ac or 230
volts
ac,
as
desired.
The
instrument
is
designed
to
be
mounted
directly
in
a
standard
EIA
19 inch relay rack.
Resilient
feet
are also provided
for
bench
top use.
grounding.
Better
than 10*0
ohms
up
to
80%
relative
humidity and
35°
C.
With
driven guard,
isolation
im-
proves by
at
least
one order
of
magnitude
up
to
1013
ohms.
Any
input
terminal
may
be
floated
1100
volts
off
chassis ground.
y
DC
COMMON MODE
REJECTION
ft
better than 160
db,
input short-circuited,
80%
relative
humidity; better than
140
db,
open-
circuited,
50%
rela-
tive
humidity; better
than 120
db,
open-circuited,
80%
relative
humidity.
AC
COMMON MODE
REJECTION
(below 100
kHz)
100
volts
rms
or
120 db greater than end
scale,
which-
ever
is
less, will effect
reading
less than
2%
of
end
scale.
Input
open-circuited.
1-4.
ELECTRICAL SPECIFICATIONS
INPUT
VOLTAGE
RANGE
1
microvolt
to
1000
volts
dc
end
scale
in
nineteen ranges,
using
XI and X3
progression.
INPUT RESISTANCE
100
megohms
onllOO
millivolt
range and above/ 10
meg
ohms
on
100- millivolt r-ange-and-below-.
Vw/
'1
(00
I
gv\e*»
accuracy
\
-
±(3% end
scale +
0. 1
microvolt).
AC
NORMAL MODE
REJECTION
(60
Hz
and
above)
AC
voltages 60 db
above end
scale
will effect
reading
less than
2%
of
end
scale.
Maximum
voltage not
to
ex-
ceed 750
volts
rms.
RECORDER OUTPUT
0-1
volt,
one
side at
chassis ground;
linear
to
0.
5%
of
end
scale.
Source impedance,
5k
to
7.
5k.
OF
ZERO
Better than
0.
15
microvolt/hr,
better than
0,
3
micro-
volt/day.
MAXIMUM
NOISE
(input
shorted)
Range
Noise
(peak-peak)
TEMPERATURE
COEFFICIENT OF ZERO
Less
than
0.
1
microvolt/
0
C
from
15°
C
to
35° C.
Less
than
0.
2
microvolt/
0
C
from
0°C
to 50° C.
1
microvolt
0.
20 microvolt
3
microvolt
0.
25
microvolt
10 microvolt
-
1000
volt
0.
30 microvolt
METER
RESPONSE
TIME
(to
90%
of
reading)
Range
Time
1
microvolt
5
seconds
3
microvolt
3
seconds
10 microvolt
-
1000
volt
1-1/2 seconds
INPUT ISOLATION
Better than lO
1
^
ohms
at
less than
50%
relative
humidity
and
25°
C
regardless
of
line,
chassis, or
recorder
ZERO CONTROL RANGE
±5 microvolt
minimum.
OVERLOAD PROTECTION
Up
to
1100
volts dc
may
be
applied
on any
range.
Typical
recovery time
is
4
seconds.
INPUT
POWER
115/230
volts ac
±10%,
50
to
440 Hz, approximately
3
watts.
1-5.
ENVIRONMENTAL
SPECIFICATIONS
OPERATING
TEMPERATURE RANGE
Within
all
specifications
from
15°
C
to
35° C.
X-l
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