What is the structure of the moving coil microphone and how is it detected?

Moving coil microphone. Generally known as a microphone.


It is an acoustic and electrical converter. A moving coil microphone consists of a diaphragm, a coil, a permanent magnet, and an output transformer. The diaphragm vibrates with sound pressure and drives the coils in it to vibrate in the magnetic field to generate an induced current. The current changes with the sound pressure of the diaphragm. The greater the sound pressure, the greater the current generated. The lower the sound pressure, the smaller the current generated (usually a few mV). An output transformer is also attached to the microphone to improve sensitivity and to match the amplifier's impedance. Transformers have two types of self-coupling and mutual inductance. There are two types of output impedance, high resistance and low resistance, depending on the turns ratio of both side coils. The output impedance of the microphone is less than 600 ohms, and it is a low resistance microphone. The output impedance is higher than 10,000 ohms and is a high resistance microphone.


Detect moving coil microphone


 (1) To detect the appearance of the structure, adopt the method of the first outside and back, if there is distortion, the sense of steel is broken, first whether the lower sound head is affected A table to check if the value of each round is similar or not.


If a silent failure occurs, first make sure that the next voice coil wiring is loose and loose, and then use a multimeter to check if it is on or off. You also need to make sure that the switch is loose, the plug is welded, and that the cord and shield are open.

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(2) Judgment of silent


Common microphones (such as family karaoke microphones), their DC resistance is 600Ω. Test the center end of the plug with a multimeter RX100Ω and open the microphone switch ON. The resistance is 600Ω. If the impedance is not measured, it is explained that there is a break in the plug switch head. This can be detected with a multimeter.


First, unscrew the front cover and measure both ends of the lead extraction line directly. Using R will prove that the inside of the voice coil is open. If R is about 600 ohms, the voice coil is good and the fault is in the plug or wire rope and switch. In such places, it is actually proven that the phenomenon of disconnection occurs frequently. For example, the screen cable capacity of the wire rope is fragile, the core wire is welded, the switch's internal contact is bad, or the connection is bad, solder removal.




(3) Serious calls are a common drawback of microphones, which are mainly caused by the following reasons. The shield cable in the cord is broken or the shield wire connected to the plug is disconnected, and only the core wire is normal. When the plug of the microphone is inserted into the socket of the amplifier, the shield wire is cut, so the ground wire is also cut, and the human body's induction and the external interference of the hand microphone are transmitted to the self-oscillation of the loudspeaker. . After replacing the sound head, the core and screen are lined with thin lines, so the two wiring terminals of Ye to the sound head will pass, so it is easy to activate the centerline docking power amplifier. The device's ground terminal screen is connected to the power amplifier's input terminal.


The microphone of the plastic cylinder shell is not a problem and does not cause howling, but the centerline is connected to a metal case, and the induction of the human body causes a power amplifier to generate howling. Use the multimeter RX100 Ω to block the test. One end of the sound head is welded so as not to form a circuit. Then turn the switch to the "ON" position. Placing it in the "OFF" position will also affect the circuit as well as shortening the center and shield lines, which will affect the test. Then use a multimeter to connect the center end of the plug to the metal shell of the microphone. The practical model prevents the human body from sensing that the core wire is not connected to the handheld metal part. Since the metal cylinder shell is connected to the terminal of the plug shield wire, there is no howling because the earth portion of the power amplifier is fixed.

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 (4) In order to detect the light and distortion of the acoustic head, loosen the front cover of the acoustic head and observe whether the vibrating film is compressed and has no elasticity. Use two stylus points at the ends of the touchhead, a multimeter RX1 file. If the sound is very low, use RX100 Ω to measure the impedance. If the impedance is about 300 ohms, a short between turns exists in the voice coil, which is