Here would like to share how I test FET transistor using digital VOM. I think it is very simple method.
Suppose we are testing n channel MOSFET. Normal MOSFET should act as described below.
1. Put the black probe on the drain pin, red probe on source pin. The VOM should show some 400 to 700 reading. It shows the MOSFET is in “closed” condition.
2. Now put the red probe on the remaining gate pin still holding the black probe on drain pin and it should show infinite resistance 1. Now bring the red probe back on source pin, voila now it should show much lower value than previous, about 50 to 250 depending on MOSFET type. Now MOSFET is in “open” condition. You can test it by disconnectiing the probes and touch again red on source pin, black on drain pin.
3. Now we will close the MOSFET. Holding the red probe on source pin, put the black probe on gate pin. It should show infinite resistance “1″. Now put black probe back on drain pin, it should show previous higher reading about 400 to 700, because we’ve just “closed” it.
That’s all. Believe me, it’s very simple method.
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