Radio Shack 22-174A - Transistor Testing Considerations; Limitations for Power and High-Frequency Transistors; Measuring Frequency; Frequency Measurement Safety and Setup

o
High-voltage
junctions
in
power
transistors
prevent
correct
readings.
Also,
the larger leads
of the
power
transistor can
damage
the
test socket Do not
try to determine type,
pin
out,
and hre for
power
transistors
with this meter.
o
The meter
displays a delault
junction
type and
pinout
if
you
press
hre when
you
have
not connected
a transistor.
The
meter defaults
to PnP
and CEb with the hrE measurement
given
as a very large
value or overflow
condition.
The
bar
graph
reading
is not
stable
-
it ranges
up and down
while
the display maintains
a
running
average of the
random
readings.
o
hre is
affected by temperature. Try not
to
warm
the transis-
tor with
your
hand
when
you
install the
device
in
the socket.
lf the hre reading is not
stable
when
you
first measure it, let
the transistor's temperatu re
stabilize.
.
Some transistors
designed to operate
at
high frequencies
show a small amount of
reverse
gain (reverse
beta).
This
can
make
your
meter
display an inconect transistor type
and
pinout.
To
be sure
you
have the
correct
pinout
and transistor
gpe,
check all
transistors twice
-
once
with
the transistor's
flat
side
facing
you
and once
with
the flat side
facing
away from
you.
The reading
that
indicates
the highest
gain
is
the cor-
rect reading.
Gaution: The
transistor
socket
is
NOT
protected
agains! over-
voltage.
You
can damage
the
meter
and void
your
warranty il
you
build and
use external leads for
the transistor socket.
MEASURING
FREQUENCY
WARNING:
IF YOU
TRY TO
MEASURE
THE
FREQUENCY
OF
A
SIGNAL
THAT
EXCEEDS
750
VOLTS
AC
RMS, YOU
MIGHT DAMAGE
YOUR
METER
AND
EXPOSE
YOURSELF
TO ASEVERE SHOCK
HAZARD.
Follow
these
steps
to
measure the
frequency
of a signal.
1. Set the
function
control
to
Hz. K Ez
appears
on the
display.
2.
Plug the
red
test
lead
into
the
+
jack,
and
plug
the
black
test
lead
into the
-COM
jack.
Black Red
3.
Connect
the
black test
probe
to a
ground
reference
for
the
signal,
and connect
the
red test
probe
to the signal
source.
The
meter displays
the
measured
frequencY
from
0 to 2.000
MHz.
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P"ffiffjm"
34
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