Radio Shack 22-812 - Checking Diodes

Making Measurements
24
4. Touch the test leads across the circuit you want
to measure.
Shrt
appears and the buzzer
sounds if the circuit resistance is less than
about 50 ohms (meaning the circuit is
continuous or shorted).
Open
appears and the
meter’s buzzer does not sound if the circuit
resistance is greater than about 50 ohms
(meaning the circuit is not continuous).
%*'%-+0)"&+1&'5
This procedure lets you check diodes, transistors,
and other semiconductors for opens, shorts, and
normal operation. It also lets you determine the
forward voltage and polarity for diodes. (This is
handy when you need to match a diode.) You can
also check LEDs using this procedure. .#
.#.#
.#
±
You can also use the meter’s
h
FE feature to quickly
measure the gain of small-signal, bipolar
transistors. See “Measuring
h
FE” on Page 27 for
more information.
1. Remove all power from the circuit under test
and discharge all capacitors.
2. Rotate the function selector to
–
––
–
/
„
„„
„
.
3. To select the diode function, press
SELECT
once.
„
„„
„
appears on the display.
4. Connect the test leads to the device you want
to check, or remove one of the leads of the
component you want to measure from its circuit
and connect the test leads to the component.
Note the first reading.
5. Reverse the test leads and note the second
reading.
If one reading shows a value and the other is
overrange (
Eý<
Eý<Eý<
Eý< appears) the device is good. If Eý<
Eý<Eý<
Eý<
appears during both readings, the device is open. If
both values are very small or zero, the device is
shorted.
±
"016'"
±
"
(continued)
its own capacitance
(see “Using Relative
Measurement” on
Page 15).
Checking Diodes
• When you test a silicon-
type semiconductor, the
values might vary
depending on the
temperature.
• The values that appear
during a diode check
show the actual forward
voltage (2.0V max). If
the voltage exceeds
2.0V,
Eý<ý
Eý<ýEý<ý
Eý<ý
appears. The
meter cannot check this
diode.
.
"%#76+10"
.
Do not connect the test
leads to a source of voltage
with the function selector
set to
–
––
–
/
„
„„
„
. This could
damage the meter or the
circuit being tested.
22-812.fm Page 24 Monday, April 8, 2002 1:32 PM