Electret microphone performance measurement circuit

 (1) Judgment of polarity The electret microphone (microphone) is composed of an acoustic-to-electrical conversion system and a field effect tube. It can be seen from Figure 6-50 that
there is a diode indirectly between the gate and source of the field effect transistor, so the forward and reverse resistance characteristics of the diode can be used to determine the drain and source of the electret microphone.
    Judgment method; turn the switch of the multimeter to the R×lktl position, connect the nested test lead to one electrode, and the red test lead to the other electrode, write down
the reading in the table} Exchange the two test leads and measure again, and write down the reading in the table , compare the two test results, and measure the smaller resistance value. The electrode connected to the black test lead
is the Ying pole, and the electrode connected to the red test lead is the mattress pole. ,
    (2) Judging the quality and sensitivity of the microphone. The picture shows the
electret microphone performance measurement circuit .
    When the sound pressure acts on the microphone, there is an output on the millivolt meter. According
to this principle, we can use the battery in the multimeter to replace
E in Figure 6150, the internal resistance of the multimeter to replace Rr in the figure, the meter head of the multimeter
to replace the millivolt meter in the figure, and use external sound sources (voices or mouth blowing) instead of
the speaker and signal source in the picture. When the sound pressure acts on the microphone, the meter will have a
certain output. Depending on whether the microphone has output, the quality of the microphone can be judged. According to the size of the output, the sensitivity of the microphone is judged.
    The test method is as follows: Set the multimeter switch to the Rx lktl position, connect the black test lead to the drain (D) of the microphone, and the red test lead to the source
(s) of the microphone. At the same time, they are grounded, blow into the microphone with your mouth, and watch the multimeter needle. The greater the amplitude of the swing, the higher the sensitivity. If the meter pointer
has no indication, it means that the microphone is invalid; if there is an indication, it means that the microphone is working normally; the size of the indication range indicates the sensitivity of the microphone .