Transistor Testing Using Multimeter.

How to test a transistor ?
Step by step instructions:

                   The instructions are given primarily for an NPN transistor as these are the most common types in use. The variations are shown for PNP varieties - these are indicated in brackets :

                    

   1. Set the meter to its ohms range - any range should do, but the middle ohms range if several
 are available is probably best.

   2. Connect the base terminal of the transistor to the terminal marked positive (usually
 coloured red) on the multimeter

   3. Connect the terminal marked negative or common (usually coloured black) to the
collector and measure the resistance. It should read open circuit (there should be a deflection
 for a PNP transistor).

   4. With the terminal marked positive still connected to the base, repeat the measurement
with the positive terminal connected to the emitter. The reading should again read open
circuit (the multimeter should deflect for a PNP transistor).

   5. Now reverse the connection to the base of the transistor, this time connecting the
negative or common (black) terminal of the analogue test meter to the base of the transistor.

   6. Connect the terminal marked positive, first to the collector and measure the resistance.
 Then take it to the emitter. In both cases the meter should deflect (indicate open circuit for
 a PNP transistor).

   7. It is next necessary to connect the meter negative or common to the collector and meter
 positive to the emitter. Check that the meter reads open circuit. (The meter should read open
circuit for both NPN and PNP types.

   8. Now reverse the connections so that the meter negative or common is connected to the
emitter and meter positive to the collector. Check again that the meter reads open circuit.

   9. If the transistor passes all the tests then it is basically functional and all the junctions
are intact.

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