Diagram of measuring buzzer and microphone with multimeter

6. Usually, the manufacturer of electret microphones provides operating voltage schemes or typical operating voltage values ​​(mostly 1.5V, 3V, and 4.5V) and maximum operating voltage (≥12V). Do not exceed the voltage limit during use, otherwise the internal field effect tube will be broken down. Except for the electret microphones of microelectronic devices that often use a 1.5V power supply, the operating voltage of most electret microphones is within the 3 to 10V scheme. A higher operating voltage is conducive to expanding the dynamic scheme of the microphone and avoiding serious distortion in situations with high sound pressure levels; if the operating voltage is too low, it will not only affect the dynamic scheme of the microphone, but also reduce the operating current of the microphone, affecting the signal-to-noise ratio of the circuit. If conditions permit, it is best to let the microphone operate at the voltage recommended by the manufacturer to obtain the best performance.

7. During electronic manufacturing or repair, if the three-terminal electret microphone is found to be damaged and there is no suitable replacement at hand, it can be replaced by a common two-terminal electret microphone of the same size and similar main parameters such as sensitivity. The specific method is as shown in Figure 4. Use a knife to cut off the copper foil of the solder pins of the two-terminal electret microphone that are not connected to the metal shell, and weld independent leads to the metal shell. Then the original two solder pins plus the metal shell (ground terminal) form a three-terminal electret microphone.

Figure 4 Obtaining a three-terminal microphone

8. When installing and using an electret microphone, it must be kept as far away from the speaker as possible, and not to be pointed at the speaker to avoid howling. When using several electret microphones together, they cannot be directly connected in parallel, but each microphone should be connected to the corresponding front expansion circuit separately, and then "combined" according to needs after expansion.

9. When using an electret microphone, keep a certain distance between your mouth and the microphone. If you keep your mouth too close, the dynamic signal will be blocked and distorted. If you keep your mouth too far away, the dynamic signal will be reduced and the noise will increase. In addition, the sound receiving hole on the front of the microphone should be pointed toward the sound source to obtain better frequency response and sensitivity. Whether the microphone is used or stored, it should be kept dry and avoid moisture. For external electret microphones, the lead wire should be retracted and released in one direction. Do not twist it randomly, otherwise it will easily cause the lead wire to break or short-circuit.