2-8
DC
VOLTAGE MEASUREMENT.
Use the Model
178
DMM
to
measure dc volts as follows:
a.
Turn on power and depress the DCV pushbutton.
b. Select the desired range from the four ranqes available. The maximum reading
is
19999.
Over
range is indicated by a flashing 0000 except on the 1OOO-volt range.
CAUTION
Do not exceed the maximum ratings.
.
Instrument damage may occur.
C .
Neqative polarity is displayed automatically.
Positive polarity is implied
when
t h e m i n u s ( - ) d i s p l a y
i s o f f .
d Zero the
instrument as described
in Paragraph 2-11 before the first use, whenever
the’instrument
is used outside the temperature range of
18"
to 28°C, and approximately
weekly ,during normal use.
2-9 .
AC VOLTAGE MEASUREMENT. Use the Model
178
DMM to measure ac volts as follows:
a. Turn on power and depress the
ACV
pushbutton.
CAUTION
Do not exceed the maximum ratings. Instrument damage may occur.
b
19999
Select the desired range from the four ranges available. The maximum reading is
Overrange is indicated by a flashing 0000 except on the lOOO-volt range. The
instrument reads the root mean square value of a sine wave with a frequency of 45 to 20
kHz.
c.
The Model
1682
RF Probe (see Paragraph 2-12e) should be used to measure ac voltages
with a frequency of 20kHz to 100MHz.
2-10.
RESISTANCE (R) MEASUREMENT. Use the
178
DMM to measure resistance as follows:
Turn on power and depress the pushbutton.
CAUTION
Do not exceed the maximum ratings.
instrument damage may occur.
b
19999
Select the desired range- from the five ranges available. The maximum reading is
Overrange is
M refers to meqohms.
indicated by a flashing 0000. The letter k refers to kilohms, and
c.
The HI input terminal is positive and causes forward conduction of semiconductor
junctions.
d
.
Two volts is applied at full range with 5 volts maximum under open circuit conditions.
Zero the instrument
as
d e s c r i b e d
i n P a r a g r a p h 2 - 1 1 b e f o r e t h e f i r s t u s e w h e n e v e r
i s u s e d o u t s i d e t h e t e m p e r a t u r e r a n g e o f
18°
to
28°C,
a n d a p p r o x i m a t e l y
w e e k l y d u r i n g n o r m a l u s e .
2-11. ZERO ADJUSTMENT. The zero adjustment nulls input offset on the 20, 200 and 1200
volt ranges and on all resistance ranges. Typically, this adjustment need
not be per-
f o r m e d m o r e o f t e n t h a n o n c e a w e e k u n l e s s t h e i n s t r u m e n t i s o p e r a t e d a t a m b i e n t
t e m p e r a t u r e s o u t s i d e t h e r a n g e o f 18° to
28°C.
Z e r o a d j u s t m e n t m a y a l s o b e u s e d f o r l e a d
c o m p e n s a t i o n o n t h e
f u n c t i o n . Z e r o t h e i n s t r u m e n t a s f o l l o w s :
a. Turn on
the power
and select DCV
and
the 20
r a n g e .
b. Plug
i n t e s t l e a d s a n d s h o r t t h e m .
A d j u s t t h e z e r o a d j u s t ( p o t R132) f r o m t h e
f r o n t p a n e l w i t h a s m a l l s c r e w d r i v e r t o o b t a i n a r e a d i n g o f 0 0 0 0 o r
- 0 0 0 0 .
2-12. ACCESSORIES. A
w i d e r a n g e o f a c c e s s o r i e s i s a v a i l a b l e t o f a c i l i t a t e u s e o f t h e
M o d e l
1 7 8
D M M ,
e x t e n d i t s r a n g e a n d a d a p t i t f o r a d d i t i o n a l u s e s .