Radio Shack 22-168A - Page 29

© Do not take the hFE 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 current.
This meter applies 500 to 1000 A to the
emitter and collector and measures the base
current to calculate the base gain.
Even though the meter tums off the test
probes during the hFE measurment, a voltage
connection might affect the hFE reading. Do
not connect the test probes to a voltage
source during this measurement.
* You cannot measure the hFE of a transistor
that is connected in a circuit.
* You cannot measure the hFE of an FET or
other non-bipolar transistor.
© Some power Darlington transistors contain an
intemal base-to-emitter resistor. Because the
meter uses two current readings to calculate
hFE, any intemal transistor resistance causes
undependable readings.
¢ 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 hFE for power tran-
sistors with this meter.
© hFE is affected by temperature. Try not to
warm the transistor with your hand when you
install the device in the socket. If the hFE read-
ing is not stable when you first measure it,
let the transistor’s temperature stabilize.
Warning: The transistor socket is not protected
against overload. You can damage the meter and
void your warranty if you build and use external
leads for the transistor socket.