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.

NPN Transistor and 2 diode model to test NPN type.

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.

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

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.

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

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.

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

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.