Elenco Diode/Transistor Tester - Manual (Page 4)

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6. When the transistor is shown to be OK, the base current control
gives an indication of transistor beta. The lower the setting
relative to another transistor, the higher the beta. Lamps NPN
and PNP measure base current. Higher base current results in a
brighter LED. It also indicates if current is entering or leaving the
base, thus, NPN or PNP respectively will light.
Transistor Testing - In Circuit
The DT-100 will test transistors in circuit, provided the base biasing
resistance is greater than 100
Ω. Simply follow the previous
procedure for testing out of circuit transistors. Do not apply power
to the circuit of the transistor or diode under test. The DT-100 will
supply the necessary power.
CHECKING OUT YOUR TRANSISTOR/DIODE TESTER
The following is a simple procedure for testing your DT-100.
Diode Operation:
1. Place the switch in the diode position. Short the black and red
leads together and push in the test button. The diode test LEDs
should alternately go on at about a 1Hz rate.
2. Connect the red and black leads to any good diode. Only one LED
should flash, identifying the red lead connection (anode or cathode).
Reversing the leads should cause the other LED to flash.
Transistor Operation:
1. Place the switch in the transistor position. Short the yellow (B)
and black (E) leads together. Press the test button. Vary the base
current control. The NPN lamp should light with the switch in the
NPN position and the PNP lamp when the switch is in the PNP
position.
2. Place a known good transistor in the test socket with the Emitter
in E, Base in B and Collector in C pins. Be sure none of the leads
are shorting. Vary the base current control. The OK LED should
light up. Note that on the NPN transistor, the NPN lamp also will
glow very slightly. This indicates the base current, and thus lower
intensity. The base current control should be adjusted for the
lowest setting with the OK lamp glowing.