Keithley 177 Instruction Manual page 14

depressed, the display
will
read
overrange,
signalling
the user to
go
to the next higher
range.
If
20M
is
depressed, the
display
will
read
zero regardless of
the voltage
applied.
The
method
of
calibrating the converter
may
yield
an
offset
up
to
125
digits
with the
Model
177 input
shorted. This
does not
affect
instrument
ac-
curacy.
2.
Select the desired
range
from
the
five
ranges
available.
CAUTION
MAXIMUM
ALLOWABLE
INPUT
VOLTAGE
(All
ranges);
1000V rms, 1400V peak,
10A/®Hz
maximum. Do
not exceed the
max-
imum
rating.
Instrument
damage may
oc-
cur.
3.
Connect
signal to
be
measured between
INPUT
HI
and
LO
terminals.
Observe the displayed
digits
and decimal
point
location.
The
200mV
range
is
direct-reading
in
mV
and
the
remaining four
ACV
ranges are
direct-reading
in
volts.
4.
The
crest factor (CF)
is
the
ratio
of the peak voltage to the
rms
voltage as follows:
There
will
be
some
additional
measurement
error
for signals
with a
crest factor greater than 3
(CF>3).
Typical crest factors are
as follows:
Sine
Wave
CF =
1.4
Square
Wave
CF =
1
Triangular
Wave
CF =
1.7
Positive
pulse
train
(duty cycle
CF =
3
is
0.11)
CF =
\Z1
/duty cycle
5.
The
optional
Model
1682A RF
Probe can be used with the
Model
177
to
measure 0.25V
to
15V rms
AC
signals
with a
frequency
of
20kHz
to
250MHz
(and
above
at
reduced
ac-
curacy).
6.
Refer to paragraph 2.14
for
TRMS
measurements
of
a
signal
with both
AC
and
DC
components.
2.11
RESISTANCE
(C)
MEASUREMENT
The
Model 177
DMM
measures
resistance
from Imfi/digit to
20Mfi.
See
Table 2-2
for ranges.
Nominal
settling
times to
within
one
digit
of
final
reading
are:
three
seconds on
the
20Q
range;
two
seconds on the 2000kS2
and
20MQ
ranges;
one
se-
cond on
the other four
Q
ranges.
Use the
Model 177
to
measure
resistance as follows:
1.
Turn
on power and
depress
the
fl
pushbutton.
CAUTION
MAXIMUM
ALLOWABLE
INPUT
VOLTAGE
(All
ranges):
350V
peak.
Do
not exceed
maximum
rating.
Instrument
damage may
occur.
2.
Connect
the
circuit
to
be measured
to the
INPUT
binding
posts
and
select
the desired
range from
the seven
available.
Table
2-2.
Resistance
Ranges
Range
Setting
Maximum
Reading
Full
Scale
Voltage**
Nominal
Applied
Current
200*
19.999
20mV 1mA
2000*
199.99
200mV
1mA
2k0 1.9999
2V
1mA
20k0 19.999
2V
100/tA
200k0
199.99
2V
10/tA
2000k0
1999.9
2V
^flA
20MO
19.999
2V
OAiiA
*
Front
Panel All
Ranges
Zero
Overrange:
Open
Maximum
Flashing
Circuit:
Allowable
0000
5V
max.
Input:
350V
Peak
**H1 binding post
(red)
is
negative.
3.
Observe the displayed
digits
and decimal
point to
measun
resistance using the
2k,
20k,
200k,
2000k and 20M(
ranges.
The
full
scale voltage
drop
for
these ranges
is
2\
which
is
sufficient to
cause forward conduction o
semiconductor junctions.
The
HI (Red) terminal
i:
negative.
To measure
a
resistance
In
parallel
with
j
semiconductor junction without turning
on
the junction
either
reverse bias the junction or select
the next higher
(
range.
The
latter
method
is
possible
because of the
om
decade reduction of applied test current,
but
will
result
in
measurement
with 3^2
digit
accuracy.
It is
suggested
tha
the 2k0 range be used
for
diode
testing.
This
range has
;
nominal
1mA
test current
and the displayed reading
is
tb
forward voltage drop
in
volts.
NOTE
The
front
panel
ZERO
control
operates only
on
the
20fl
and
2000
ranges.
It
has
no
effect
on
the
other
resistance
ranges.
4.
Before
making measurements on
the
200
or
2000
ranges
adjust front panel
ZERO
on
the
200 range
to
compensat
for test lead resistance.
Best performance
will
be obtains
on
the
low
ohm
ranges
when
test
connections
are
made
t
the binding posts, rather
than using
banana
plugs. Adjus
ZERO
and make
resistance
measurements
as follows: