Keithley 153, Instruction Manual, Page: 12 / 51

OPERATION
2-3.
PRELIMINARY PROCEDURES.
a. Check t h
e 117-234
S w it c h and the Fuse for t h e proper ac line voltage.
h.
Set the controls as
follows:
METER
Switch
RANGE
Switch
FUNCTION Switch
POWER
OFF
1 VOLT
VOLTS INPUT R-2M
Check
meter z
e
r o
.
If
n
e
c e s s a r y ,
adjust with
the
meter
m
e
c
h
a n ic a l zero.
MODEL
153
c.
Connect
t h e
power cord
and set the
METER
Switch
to +.
W
i
t h
i
n one minute, t
h
e meter
needle should be
at z
e
r
o
with
the
input shorted.
If
t
h
e
meter
is not
e
x a ctl y at zero
w
i t h the input shorted after approximately
20
m i n u
t
e
s ,
adjust the
internal BIAS ADJ Po­
tentiometer, R12S
for e
x a c
t me ter zero.
(See paragraph
5-5.)
For
maximum
accuracy, al­
low
the
Model 153
to
warm
up approximately
30 minutes.
d. To cancel any zero o ffs e
t
,
short the input high
to
low
and reduce
meter
sensitivi­
ty.
Ad j ust the front p a
n
e
l ZERO
Control.
2-4. VOLTAGE
MEASUREMENTS.
a.
V o lt
a
g
e
measurements can be made with either of two input resistances:
2
megohms
for all r
a ng
e
s
, or a
h
i
gh
e r
resistance,
from
20
m
e g
o hms to
200 me g
o
h m s
depending upon
t h
e
r a n g
e
.
1.
Generally, it
is
b
e
tt
er
to
use the higher input resistance
(obtained by s e
t
ti n g
the
FUNCTION
Switch t o
VOLTS OPEN).
To maintain the accuracy
of
measurements, the
in­
put r e si
s
t
a
n
ce
should
be 100 times the
s o ur c
e
resistance.
(See Table
1-1
for input
resistance by ranges.
2. With the higher input resistance, some meter deflection
may
occur with the
input
open due to extraneous siRna1 pickup.
To
reduce this pickup and also
to
speed
recovery
from input overloads when measuring
low
impedance sources, use the 2-megohm input
resis­
t a n
c
e
(obtained by
setting the
FUNCTION
Switch to
VOLTS
(R-2M).
h.
Connect
the
voltage s o u r
c
e
to
t h
e
INPUT
Receptacle. Use properly
shielded and
g r
o
unde d leads. Refer to paragraphs
2-8
and following for suggestions and
cautions.
c.
S
e
t the RANGE
Switch t
o
the highest
voltage range. Turn the
METER
Switch
to
CENTER
ZERO
for
the correct p
ol
a
r
i t y for the input
signal.
Increase the Model
153
sensitivity
until the meter shows the greates t on-scale deflection. On t h
e
3-volt and higher ranges,
the
Model 153
will
withstand overloads
to
1000
volts without
damage.
On the lower ranges,
momentary overloads
to
1000
volts will cause o n
l
y temporary instability
and
zero offset.
Prolonged
overloads will d a m a g
e
components and cause i n c r
eas
e
d noise and
sl o w e
r
response
speeds.
6