Radio Shack 22-812, Owner'S Manual

Page: 23 / 32

23
Making Measurements
Note: If your measurement exceeds
the currently selected range,
EEEEý< ý< ý< ý<
ap-
pears until the measured voltage or
current is reduced to a value below
the currently selected range.
MEASURING
RESISTANCE
The resistance measuring circuit in
your meter compares the voltage
gained through a known resistance
(internal) with the voltage developed
across an unknown resistance.
WARNING: Be sure the circuit under
test has all power removed and any
associated capacitors are fully dis-
charged before you make a resis-
tance measurement.
Caution: Your meter has a circuit to
protect the resistance range from
over-voltage. However, to avoid acci-
dentally exceeding the protection cir-
cuit’s rating and to ensure a correct
measurement, never connect the test
leads to a source of voltage while the
function selector is set to
• • • •
.
1. Remove all power from the cir-
cuit under test and discharge all
capacitors.
2. Rotate the function selector to
• • • •
.
Caution: Never connect the test
leads to a source of voltage while
the rotary function selector is set
to
•
• •
•
.
3. If necessary, press
SELECT
until
Ω Ω Ω Ω
,
K
Ω Ω Ω Ω
,
or
M
Ω Ω Ω Ω
appears to set the
meter to measure resistance.
Note: With no resistance con-
nected across the test leads
(meaning resistance is infinite),
EEEEý < ý < ý < ý <
appears when you set the
meter to measure resistance.
This is normal.
4. Touch the test leads across the
resistor you want to measure, or
remove one of the leads of the
component you want to measure
from its circuit and touch the test
leads across the resistor. If the
meter is set to automatic range
control, it automatically moves to
the proper range.
If you set the meter to use manual
range, repeatedly press
RANGE
to set
manual-range control and change the
range (if necessary).
Notes:
• If you are measuring resistance
of about 1M
Ω
or more, the dis-
play might take a few seconds to
stabilize. This is normal.
• As with the voltage range, use
the measuring units that appear
on the display to determine the
current resistance range. If only
Ω Ω Ω Ω
appears, the values of the
measurements are in ohms. If
AAAA
and
Ω
Ω Ω
Ω
appear, the meter is mea-
suring kilohms (1 kilohm =
1000
Ω
). If
C
C C
C
and
Ω Ω Ω Ω
appear, the
meter is measuring megohms (1
megohm = 1,000,000
Ω
).