Radio Shack 22-174A - Checking Diodes; Diode Test Procedure and Interpretation

CHECKING DIODES
This lunction leb
you
check diodes and other semiconductors
for
opens and shorts. lt
also
lets
you
determine the
forward
voltage for diodes. You
can use this
function when
you
need
to
match diodes.
Reverse the
probes
or
reverse
the
component
in
the socket, and
note the
second reading.
lf
one
value is normal and the
other
is
overrange,
the
component
is
good.
lf
both
values are over-
range,
the component
is
open. lf both
values are
very
small
or zero, the
component
is
shorted.
Notes:
The value indicated by
the bar
display during
the clig$e
check function
is the fonrard
voltrage
(approX.2.5
V max.).
When
the
diode
is reverse biased,
the
display shows
the
normal
ovenange
indication,
but the bargraph
shows
25.
This reading
is
the
actual open+ircuit
(reverse
biased)
volt-
age.
(2.45
volts appears as
25 on the bargraph.)
lf
the display
shows a
low
voltage reading,
the
red test
probe
is allhe anode of
the diode
and the black
probe
is
at
lhe cathode
(banded
side)
of the diode.
This
condition
is
called the
foruard biasd condition.
lf the
diode
is in
a
forward biased
condition
and
if
you
use
the DloDgoHMgcAP to
test the diode,
the
anode
is
at
the +
side ol the socket
and the cathode
is
at the
banded
(-)
side.
This meter
supplies
enough
fonrvard voltrage
to
light most
LEDs. This lets
you
determine
if an LED
is
good
and
which
lead is the cathode.
1.
Set the
function
control to
#
-or
appearson
the display.
2. Plug the red tgst lead into
the +
jack
and the black
test lead into
the
-COM
jack.
ro
-cou
*
4
*"@fl9^Qtr
----I
l l
Black
Red
3.
Remove
power
from
the
circuit
under test.
4.
Connect
the
probes
to
the
component
you
want to
check
and note the
display. Or, connect the
component
you
want to
test
to the DloDgoHMg
CAP test socket and
note
the display.
DroDE/OHMS/CAP
30
31