Tuesday, December 8, 2020

Test NPN PNP transistor with a digital multimeter and identify transistor pinout

Test  NPN  PNP   transistor   with  a   digital    multimeter 

Test condition of  electronic   component   start  with  test   resistor , capacitor , diode , LED , and the next component is  transistor.   Before testing  transistor  you have to study how to test diode firstly  because it the same process just  more detail.   The parity of  test  leads  and  diode , forward bias , reverse  bias  also use to describe how to test transistor.   Diode model is used to explain how to test transistor.   NPN type 2 diode is common anode connection   and  PNP type 2 diode is common kathode connection.



Test  NPN  PNP   transistor  check

NPN   Transistor and   2    diode model  to test  NPN  type.




Test   NPN  PNP   transistor

                                     PNP   Transistor and   2    diode model  to test  PNP   type.



Step to  test    transistor   with  a   digital    multimeter .

1. Turn the range switch to  diode test.

2. Connect the test  lead with B and C terminal and read the measured value.  Then switch the test leads and  read the measured value again .  Good transistor will  display  0.5-0.7V    1  time  and  "OL"  1 time. Shorted transistor  will  display 000V  2 time  and  open transistor  will  display "OL"   2 time.


 The  terminal   arrangement   of   example  transistor for  test demonstration.  Different transistor part   number may   has  different terminal  designation.


Test  NPN  PNP   transistor
       B  and C terminal  test , good transistor will  display  0.5-0.7V    1  time.



Test   NPN  PNP  transistor
   B and C terminal  test , good transistor will  display  "OL"   1 time. ( switch the test leads )


3. Connect the test  lead with B and E  terminal and read the measured value.  Then switch the test leads and  read the measured value again.   Good transistor will  display  0.5-0.7V    1  time  and  OL   1 time. Shorted transistor will display 000V  2 time  and  open  transistor  will  display  OL   2 time.

Test  NPN  PNP   transistor
           B  and  E   terminal  test , good transistor will  display  0.5-0.7V    1  time.



Test  transistor
  B  and E  terminal  test , good transistor will  display   OL   1 time. ( switch the test leads )


4. C and E  terminal test , connect the test  lead with C and E  terminal and read the measured value.  Then switch the test leads and  read the measured value again.   Good transistor will  display  OL   2  time and  shorted transistor will display 000V  2 time.  

5. All  step of  testing  must  be  all  good condition  so the transistor is  still  good  ( step 2 , 3 and 4 :  B-C terminal test , B-E terminal ,C-E terminal test).   If   there is only any of  1 step  fail   , that transistor   is  bad.


Test transistor
                 C and E  terminal test  ,   good transistor will  display  OL   2  time


Transistor   test
   C and E  terminal test  ,   good transistor will  display  OL   2  time ( switch the test lead )



Identify  transistor pinout.

1.  Find  B  terminal ,   from   2   diode model  at  the beginning  ,   random the test around   6 times and you will find 2 time that the meter display  0.4-0.7V , the  B terminal is  connect with any test lead (not move) and make  the other test lead that  move to terminal no.2 and no.3 and meter  display  0.4-0.7V  2 time ( B-C , B-E). From  2 photo below so the red test lead is  B  terminal.

2.  Find  C and E  terminal ,  V BE  >   V BC  ,  V BE  is more than V BC so  terminal  No.3 is  E terminal  and   terminal  No.2 is  C  terminal.


Transistor  test
                                 Hold   the  red test lead with terminal no.  1


Transistor  Test 
Hold   the  red test lead with terminal no.  1


Transistor  test