Test electronic components with multimeter: Multimeter test EX3 test mosfet with digital and analog multimeter

Test mosfet with digital and analog multimeter

A power component has high current , high wattage may be broken as shorted condition and open condition. Before other process testing , you may firstly check shorted condition and open condition. Testing mosfet has some detail and all steps of testing must be good so it is a good mosfet. If any of only testing step is fail , the mosfet is already broken.

N Channel MOSFET Symbol

P Channel MOSFET Symbol

Step to test mosfet with a digital multimeter

1. Discharge mosfet . short 3 terminals D-G-S together by using resistor legs or other metal wire. then remove resistor leg. After shorting 3 terminals , do not touch any mosfet terminal again. If you touch it by error , it must re-discharge. The area which can touch and hold is the black case of mosfet.

2. Test G and D terminal , read the measured value. Switch the test lead and read the measured value again. A good mosfet , meter will display "OL" 2 time.

Discharge mosfet . short 3 terminals D-G-S together , G D S is terminal arrangment.

Test G and D terminal. The first testing.

Test G and D terminal. The second testing ( switch the test lead)

3. Test G and S terminal , read the measured value. Switch the test lead and read the measured value again. A good mosfet , meter will display " OL" 2 time.

Test G and S terminal. The first testing.

Test multimeter Test mosfet with multimeter

Test G and D terminal. The second testing ( switch test lead)

4. Test D and S terminal. Use Ohm range to test D and S terminal and read the measured value. then switch the test lead and test again. A good mosfet will display " OL " 1 time and display high resistance 1 time. Some model of mosfet has internal diode connect across D and S terminal , this case you can use diode range to test it. Bad mosfet will display differnt ways that is , shored will display very low resistance 0 Ohm 2 time , open mosfet will display " OL" 2 time.

Test D and S terminal. Use Ohm range will display high resistance 1 time.

Test D and S terminal. Use Ohm range will display " OL " 1 time.

Please be careful after discharge mosfet ,don't touch any terminal. Always hold mosfet at insultated case.

Step to test mosfet with a digital multimeter

1. Discharge mosfet . short 3 terminals D-G-S together by using resistor legs or other metal wire. then remove resistor leg. After short 3 terminals , do not touch any mosfet terminal again. If you touch it by error , it must re-discharge. The area which can touch and hold is black case of mosfet.

2. Test G and D terminal. Set range to Rx10K and do zero ohm adjustment. Connect test lead with D and G terminal then read the measured value. Switch the test lead and read the measured value again.

Good mosfet , the pointer will point at ∞ 2 time.

3. Test G and S terminal. Set range to Rx10K and do zero ohm adjustment. Connect test lead with G and S terminal then read the measured value. Switch the test lead and read the measured value again.

Good mosfet ,the pointer will point at ∞ 2 time.

Test G and D terminal. Good mosfet , the pointer will point at ∞ 2 time.

Test G and S terminal. Good mosfet , the pointer will point at ∞ 2 time.

4. Test D and S terminal. Set range to Rx10 ( or Rx100 ) and do zero ohm adjustment. connect test lead with D and S terminal then read the measured value. Switch the test lead and read the measured value again.

Good mosfet ,the pointer will point at low resistance 1 time.

Good mosfet ,the pointer will point at ∞ (or high resistance ) 1 time.

( some model it will point at high resistance instead of ∞ )