Radio Shack 22-174A - Measuring Resistance; Resistance Measurement Safety and Procedure

MEASURING
RESISTANCE
WARNING:
BE
SURE THE
CIRCUIT
UNDER TEST HAS
ALL
POWER
REMOVED
AND ANY
ASSOCIATED
CAPACITORS
ARE
FULLY DISCHARGED
BEFORE
YOU MAKE A
RESIS-
TANCE MEASUREMENT.
The resistance
measuring
circuit
compares the voltage
gained
through a known
resistance
(internal)
with the voltage
oevel-
oped across lhe
unknown resistance.
So, when
you
check
in-
circuit resistance,
be
sure the
circuit under test has
all
power
removed
(all
capacitors
are
lully
discharged).
As
with
the voltage
range,
use the
measuring
unit
displalqto
determine
the
current resistance
range.
lf
only e appdais
on the
display,
the values
of
the measurements
are in
ohms.
lf
K
and Q
appear
,
the meter
is measuring
kilohms
(the
reading
x 1000).
lf
M
and e
appear,
the meter is
mea-
suring
megohms (the
reading
x 1,000,000).
The
meter
has
a fuse
and
a special
circuit
that
protects
the
lesisJance
ranges
from
over-voltage
(voltages
greater
than
5 volts).
lf
you
blow
the meter's
fuse,
the
meter
does not
op
erate
correctly
in
the
ohms mode.
Check
the
fuse
if
the me.
ter displays
0 for
all resistance
measurements,
or
if
it
dis-
plays
other
unusual
readings.
3.
Connect
the
probes
across
the
circuit
to
be
measured,
or
plug
the
resistor
under
test into
the
oHMS/DtoDE/cAp
sockel.
lf
the resistance
is
greater
than
1 megohm,
the
display
takes
a
few
seconds
to stabilize.
This
is
normalfor
high-
resistance
measurements.
\*7
Reslstor
l+
o {F
-
[cf:-
c-]
+
\CIMY
DtoDE,/oHys/clp
Notes:
Set the function
control to
Q . O appears
on the
display. lf
there is no
resistance
connected
to
the
meter,
the meter
sets
itself
to
the
highest
measurement
range if
the
meter is in
the auto mode.
When
the
display shows
u Q, the
overrange
indication
also
appears.
2. Plug the red
test lead into
the +
jack
and the black
test
lead
into
the
-COM
jack.
Black Red
26
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