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2. With the power switch
off, the battery
charge circuitry
is
automatically
energized
to charge the battery
et the maxi-
mum rate. When the battev
pack is first installed,
or if it
has completely
discharged,
allow it to charge for at least 14
hours in this condition.
NOTE
For maximum
battery
life, do not allow the bat-
tery pack to remain completely
discharged.
Con-
stant charging
will not harm either the battery
pack or the instrument.
The Model 177 may be
operated
up to six hours from fully charged
bat-
teries.
However,
since
10 charge/discharge
cycles
may be required
to reach
full batten/
capacity,
less than six hours DMM operation
can
be expected
when the battery
pack is first in-
stalled.
3. When the Model 177 DMM is in use on line power, the bat-
tery charger maintains
a trickle charge on the battery pack.
2.7 OPERATING
INSTRUCTIONS
The basic operating
instructions
for the Model 177 DMM are
outlined
in the following
steps, and condensed
operating
in-
structions
are provided
on the bottom
cover of the instru-
ment and contained
in Table 2-l.
These instructions
should
only be used after becoming
completely
familiar
with
the
operation
of the Model 177 through
day-to-day
use. Until this
familiarity
has been achieved,
best performance
and safest
operation
will be obtained
by using the individual
instructions
provided
in this section.
Refer to Figure 2-3 and operate
the
DMM es follows:
1. Turn on the power by depressing
the ON/OFF
pushbutton
and allow
a 10 minute
warm-up
time.
Allow
additional
warm-up
for zero stability
on lowest DMM and Q ranges.
2. Select
the function
with
the AC/DC,
R, V, or A push-
buttons.
3. Select
the range
by depressing
the appropriate
push-
button.
4. Connect
the source to the INPUT terminals.
Accessories
described
in Section
1 should
be used as required.
CAUTION
Do not exceed the maximum
input ratings
shown
below.
DCV
ACV
DCA. ACA
R
QOmV,
ZOmV,
ZVI:
450V
rms continuous;
1200V
peak
momentan/,
for
up
to
eight
seconds
per minute maximum.
(20.12OOV):
12OOV peak.
;I
;;;ges):
1OOOV rms;
1400V
peak;
.
(All Ranges):
ZA, 250V
DC or rms (fuse pro-
tected).
(All Ranges):
350V peak.
2.9 ZERO ADJUSTMENT
The front panel zero adjustment
provides
compensation
for
test lead resistance
and thermal
EMFs generated
in the cir-
cuits connected
to the DMM input terminals.
The zero adjusr-
ment is operative
on the 20mV and 200mV
ranges of DCV.
20 and 200R ranges and all DCA ranges. In general, the zero
must be readjusted
whenever
the function
is changed and the
measurement
is to be made on a range where the zero adjusts
ment is operative.
The accuracy
specifications
assume that
zero is adjusted
on the lowest range of the function.
Where
applicable,
a specific
zero adjustment
instruction
is provided
in the description
of how to make the particular
function
measurement.
2.9 DC VOLTAGE MEASUREMENT
The Model
177 measures
DC voltages
from
l,lV/digit
to
12OOV. The maximum
displayed
reading is 19999. Overrange
is indicated
by a flashing 0000 except on the 12COV range. On
the 1200V range, the display can read beyond
the maximum
allowable
input voltage.
Use the Model 177 to measure
DC
volts as follows:
CAUTION
Do not exceed the maximum
input voltage
ratings,
or instrument
damage may occur.
1. Turn on power
with ON/OFF
pushbunon
and select DC
with the AC/DC
pushbutton.
2. Select the desired range from the six ranges available.
The
decimal
point is positioned
by the range pushbuttons.
The
1200V DC range is selected
by the 1000 pushbutton.
NOTE
The 20M pushbutton
is inoperative
for DC volts.
If this pushbutton
is inadvertantly
depressed.
the
Model
177 will
read
zero
regardless
of the
voltage
applied and the eight second per minute
overload
rating will apply.
3. Connect
the signal to be measured
between
the INPUT HI
and LO binding
posts.
The binding
posts accept
wires,
spade lugs or banana plugs for ease of connecting
the cir-
cuit to be measured.
Low thermal cabling and connections
are recommended
for measurements
on the 20mV
and
200mV
ranges.
4. For the top four
ranges.
merely
observe
the displayed
digits,
polarity
sign and decimal
point locations.
The top
four ranges
are direct-reading
in volts.
Nominal
settling
time is located to within
one digit of final reading.
5. For the 20mV and 200mV
ranges,
the front panel ZERO
must be adjusted
to obtain
rated accuracy.
This adjust-
ment
is necessary
to
compensate
for
thermal
EMFs
generated
by
the
connections
to
the
circuit
to
be
measured.
These voltages
may be only a few microvolts
or
several tens of microvolts.
The zero adjustment
span is set
up at the factory
to allow at least f75,tV
adjustment.
To
adjust zero, proceed
as follows:
2-3
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