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INSTRUCTION
MANUAL
Digital
Multimeter
Models
172A.
173A
OPERATING
INSTRUCTtONE
3-6.
HOW TO MEASURE CURRENT. (MODEL 172~0~~~).
The Modell72A
measures
ac and dc current
in two
ranges:
0.3A,
and 2A.
The current
is
limited
by the
current
fuse
even
thouqh
the
DMM is capable
of
displaying
2.9999A.
CAUTION
A
The Model
172Ais
protected
by a 2 ampere
fuse
on all
ranges.
If
the
fuse
is blown,
a replacement
Keithley
Part
No.
FU-13
should
be installed
in the
rear
panel
fuse
holder.
(See Figure
2-l).
a.
DC Current.
The Model
172Adetects
dc currents
from
?I0
microamperes/digit
to r2
amperes.
When the
input
exceeds
2 amperes,
the
current
fuse
will
blow.
When using
the
MAN mode it
is
possible
to select
30A,
300A t 3000A
Ranges,but2A
Max is still
the
limit.
1.
Set
to DC Amperes.
2.
Set
to AUTO.
3.
Connect
the
signal
to be measured
at
the
HI terminal.
4.
Observe
the
displayed
digits,
polarity
sign,
decimal
point
location,
and measure-
ment
unit
(mA, or A).
If
no polarity
sign
is
indicated,
a positive
polarity
is
implied.
b.
AC Current.
The Model
l7ZA
DMM detects
ac currents
from
IO microamperes
rnsidigir
to 2 amperes
vn5.
When the
input
exceeds
2 amperes,
the
current
Fuse will
blow.
1.
Set
to AC Amperes.
(The AC indicator
should
be lighted).
2.
Set
to Auto.
3.
Connect
the
signal
to be measured
at
the
HI terminal.
4.
Observe
the
displayed
digits,
decimal
point
location
and measurement
unit
!AC
mA or AC A).
FIGURE 3-2. Typical
Model 172ACurrent
Display
(DCmA).
3-r
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