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Polarity
(Negative
in
indicated, positive
is
implied
when
minus {—
)
display
is
off.)
NOTE
Due
to
the long thermal time constant
of
the
20mV
range
zero,
a
one
hour
warm-up
time
may
be necessary
to adjust
zero
to the
final
VV
set-
ting.
Typically,
only a
one
to three microvolt
zero
shift
can be expected
during
this
warm-up
period,
if
the
ambient temperature
Is
within the
specified
18° to
28°C and
the instrument has not
been
subjected
to
temperature
outside of
this
range.
Thus,
since the
expected
zero
shift
is
both
small
and
slow,
normally zero can
be
ad-
justed
and
several
measurements
taken without
having
to
achieve the
final
zero
setting.
A.
Make
connections
to
the
Model
177 as described
above. For the best performance, connections should
be
made
to
the binding posts
rather
than using
banana
plugs.
B.
Set
the
Model
177
to
the
20mV
range.
C.
Disconnect
the leads
at
the
circuit
to
be
measured and
short
them.
D.
Allow
the thermal
EMFs
generated
at
the
connections
to
stabilize.
E.
Adjust the
front
panel
ZERO
knob
for a
display indica-
tion
of
O.OOOmV
(a
flashing
±0.001mV
is
permissible.)
NOTE
The
ZERO
control
operates only
on
the
20mV
and
200mV
ranges.
It
has
no
effect
on
the other
DC
voltage ranges.
F.
Make
the
measurements by
applying the
signal
and
reading the
mV
on
the
display.
Nominal
settling
time
for
the
20mV
range
is
three
seconds
to within
one
digit
of
final
reading.
NOTE
An
overload
input to
the
Model
177
may
cause
temporary
zero
shift
due
to
thermal
gradients.
G.
The
zero
setting for
the
20mV
range
will
also
be
valid
for
the
200mV
range.
Nominal
setting
time
for
the
200mV
range
is
one second
to within
one
digit
of
final
reading.
6.
The
optional
Model 1600A
High Voltage Probe can be
used
with the
Model
177
to
measure
DC
voltage
up
to
40kV,
at
reduced
accuracy.
2.10
AC
VOLTAGE
MEASUREMENT
The Model
177 measures
AC
voltages
from
10/tV to
1000V.
The
instrument
measures
the
true root
mean
square
(TRMS)
of a signal within
the frequency
range
of
45Hz
to
20kHz.
The
maximum
reading
is
19999.
Overrange
is
indicated
by
a
flashing
0000
except
on
the
1000V
range.
On
the
1000V
range, the
display
can
read
beyond
the
maximum
allowable
input voltage.
The
maximum
crest factor for rated
accuracy
Is
3.
AC
accuracy
Is
specified for
2000
counts
and
above.
Nominal
settling
time
for
aii
AC
voltage ranges
is
2.5
second
to within 10
digits
of
final
reading.
Use
the
Model
177
DMM
to
measure
AC
volts
as
follows:
1.
Turn on
power
and
set
the
AC/
DC
pushbutton
to the
in
or
AC
position.
Depress
the
V
pushbutton.
NOTE
The
20ju
and
20M
ranges
are inoperative
for
AC
volts.
If
the
20/4
pushbutton
is
inadvertantly
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