As the FET structure, principle and common transistor different conditions in the amateur use multimeter to determine the method is not the same as before the test what your hands touch touch water pipe, or ground, to let go of the body's charge.

1.G pole (gate) of the judge: multimeter with R × 100 files, each FET were measured resistance between two feet (both positive and negative to the test once), there should be a pair of feet to several hundred ohms resistance (such as are high-value,
then the two tables document stuck with two legs, black ink and then point to another foot, such as the still high resistance, and then the other foot red pen point, the total time in a low-resistance feet circumstances, such as the lack of them, tubes should be corrupted) then multimeter connected the two tables document the pin is very D (drain) and the S pole (source), on the other foot are large resistance is G pole (gate).

2.D pole (drain), S pole (source) of the judge: multimeter put R × 10 stalls, will be red, black table document stuck in determining whether the D, S pole on the positive and negative poles were measured to resistance value, the measured resistance value is larger, with black table pen and most G (gate) contact with, and then restore the status quo, in this process, red, black ink should always be compared with the original pin contact, Then multimeter readings, two things occur: if the reading from big to small, the multimeter connected black ink by the pin for the D pole (drain), red table document received by the pin for the S pole (source); If the multimeter reading did not change obviously, still is greater, then the black table document should maintain contact with the pin, then move the red sheet document and most G (gate) and touch. At this point, if resistance from big to small, black pin-connected table document the pole for the S (source), red table document received by the pin for the D pole (drain).

3. Type of determination: determine the D pole (drain) and the S pole (source), if the multimeter connected to the black tables document the most D (drain), then red table document the S pole to S pole (source), brush hair with a black sheet and G (gate) pole, then indicate that the N-channel FET; if access to the black table document the S pole (source), red table document is very connected to D (drain), and Xu Yong-hong table document to trigger the G pole (gate), then that for the P-channel FET.

4. Transconductance determine the size: for N-channel FET, with the S pole of red table document access (source) D black table document access most (drain), multimeter reading should be greater this time if the use of 100K resistors at one end press the D pole (drain), again the most G (gate), multimeter reading will change, the change is evident, indicating that the greater the FET transconductance.

For the D-channel FET, connected with black table document S pole (source), red table document access most D (drain), the same way as before.

Some very hands touch G (gate) of the method to test also, but could easily lead to breakdown failure.

Some high-power tube, S pole (source) and D pole (drain) and have a reverse diode , testing should be considered in this situation.

Field effect transistor - transistor combination of tubes, also according to the method of testing.