Radio Shack 22-174A - Checking Transistors; Transistor Pinout, Type, and Gain Measurement

Follow
these
steps
to
determine
a transistor's
pinout,
type, and
base
gain.
1.
Disconnect
the
test leads
from
the
meter.
Voltage
connections
might
affect
the hre reading.
++
2. Plug
a transistor
into
the
hFE
socket.
3. Set the function
control
to
hFE. hrE
appears
on
the
display.
The meter
displays
the
transistor
type
(upu
or
PnP)
for
several
seconds.
Then
the meter
displays
the transistor's
pinout.
The
three letters
it
displays
correspond
to the
three
terminals
of the nre
socket. For
example, if
the meter
displays
uuc,
the far left
lead is
the
emitter, the middle
lead is
the base, and
the
far
right
lead
is
the collector.
aro16a
Pr^P
EEI
k
Ebt
Notes:
o
Do not take the
hre reading as an absolute
measurement,
but
rather as an
indication
that
the transistor
is operating.
The
true
gain
of a transistor depends
on
its
operating cur-
rent. This meter applies 500 to
1000
pA
to the emitter and
collector and
measures the base
current to calculate the
base
gain.
o
You
cannot
measure the hre of a transistor
that is con-
nected in a circuit.
You
cannot
measure the hre of an
FET
or
other non-bipolar
transistor.
Some
power
darlington
transistors contain
internal base-to-
emitter resistors.
Because the meter uses two
current read-
ings
to calculate
hre, any
internal transistor
resistance
causes undependable
readings.
rF
After
another short
pause,
the
meter
displays the
actual hre of
the
transistor. This value
ranges from 1
to 39,999.
The
meter
continuously
displays
the hre,
even
if
you plug
another
transistor
into
the socket.
To force the
meter
to
re-
examine the transistor
type and
pinout, press
TEST after
you plug
in the
new transistor.
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