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OPERATING INSTRUCTIONS
MODEL 616
FIGURE
10.
Operation
As
An Ohnmeter in
NOSM/i.L
Mode
3-8.
O PE
FaT
I
ON
a
s
A.N
OHMME
TER.
The Model 616 can
be used to
measure resistance from
1
ohm
to
2
x
ohms.
Although
the
Model
616
is
useable
as a
general
pxirpose
chmmeter.
;lr.
has certain characteristics
which enable
rellahlt'
Tseasurements
of
very large
resistances with
fast
response,
a.
Normal Mode Ohm
s
Measu
re
ments.
In this,
mode
^
the
Model
616
measures resistance over
a
wide range.
The
use
o:t
the
NOPM/U.
mode
is
recommended
for
measurements
up to
10^^'
ohms
(use
the
FAST mode
for
larger resis-
tances).
The Model 616 uses
a
constant current method
i'or
seasuriiig
resistance.
Therefore,
the
digital
Make connections
to
the
Model
616
using
a
shielded
triaxial cable.
Keep cable length
as
short
as
possible
to
reduce
the
slowing effects
ot
cable
capacitance.
The nero
control
luay
need occasional
adjustment
to
reduce any voltage
offset,
which may
occur due
to the
temperature
variations,.
To
rezero
the
Model
616,
se't
the ZERO CHECK
Switch
to
CHECK
position
and
adju.st
the front panel ZERO
control
for
a
O-O-O-O display.
(The re^commended war-mup
time
for
the
Model
616
is
two
hours,
although
it
.is
useable
immediately after power
is
turned on.)
Tfic
Model 616
provides
a
direct reading display with automatic
decimal point position.
the input terminals where
V =
I
x
R (the
current
I
is
selected in decade
steps using the RANGE Switch)
.
To
use
the
Model
616
as
an
obrnmeter,
set the
front panel
controls
as
follows:
RANGE
—
10^
OHMS
(or
other appropriate range)
SENSITIVITY
—
AUTO
FAST /NORMAL
—
NORMAL
TABLE
3-5.
Ohms Settings
Source
Res
is
tance
Range
Setting
Sensitivity
Setting
Digital
Distlav
Typical
Accuracy*
i
lo?-^
100
V
100.0
±
51
d
io"
10
V
10.00
+
51 d
lojf
1
V
1.000
+
51
d"
lof^
1
V
1.000
+
51
d
ioi°
loH
1
V
1.000
+
51
d
lo!
10^
1
V
1.000
±
51
d
10°
1
V
1.000
±
21
d
lol
1
V
1.000
±
6
d
IQ?
10?
1
V
1.000
+
6
d
10?
1
V
1.000
±
6
d
iS
10^
1
V
.1000
+
6
d
10^
10c
100 mV
.01000
+
6
d
10^
10^
10
mV
.00100
±
2 d
*exclusive
of noise, zero drift, and
loading error.
Fast
Ohms Measurement.
In this mode, the
Model
616
measures very
large,
resistances with
7-esponse (use this
mode
for
resistances larger than
10^^ ohms).
When
the
FAST/NORMAL switch
is
set
to
FAST, the
unknown resistance
(Rx)
is
floating
with respect
to the
low side of the voltage ampli-
fier.
The
unknown resistor
is
connected
across the
feedback
so as to
reduce
the
effects
of
capacitance
and therefore
speed up
the
measuring
time.
To use
the
Model
616 for
FAST ohmmeter measurements, set
the front
panel controls
as
follows:
12
RANGE
—
10
OHMS
SENSITIVITY
"
AUTO
FAST/NORMAL
—
FAST
Connect
the
unknown resistance between
Input HI and
GUARD
(on the
rear panel)
NOTE
When
the
FAST mode
is
used for resistance
meas-
urements,
the
unknown resistance sample
is
con-
nected
in
feedback around
the electrometer
amplifier.
Therefore
the
resistance
must
be
floating and not referenced
to
LO.
10
0374
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