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

Last Update Time: 2019-01-02 15:05:41

Moving coil microphone, commonly known as microphone.

It is an acoustic and electrical converter. Moving coil microphone consists of diaphragm, coil, permanent magnet and output transformer. The diaphragm vibrates with the sound pressure, and drives the coil in it to vibrate in the magnetic field to generate induced current. The current varies with the acoustic pressure of the diaphragm. The larger the sound pressure, the greater the current generated; the smaller the sound pressure, the smaller the current generated (usually a few milli V). In order to improve its sensitivity and match the impedance of the amplifier, an output transformer is also installed in the microphone. The transformer has two kinds of self coupling and mutual inductance. According to the ratio of turns of the two side coil, its output impedance has two kinds: high resistance and low resistance. The microphone output impedance is below 600 ohms, and is a low resistance microphone. The output impedance is higher than 10 thousand ohms and is a high resistance microphone.

Detect the moving coil microphone

 ( 1 ) To detect the appearance of the structure, we should adopt the method of the first outer and the back, when there is distortion, we should first whether the lower sound head is affected,and the sense of steel are broken and then use the table to check whether the value of each round is similar.

If there is a silent failure, you should first spring the next voice coil wiring is loose, bad contact, and then use the multimeter to check whether there is any on-off; it is also necessary to check whether the switch is loose, whether the plug is welded or not, and whether the core wire and the shielding wire of the cord are open or not.


( 2 ) Judgement of silent

General microphone ( such as family karaoke microphone ), its DC resistance is 600Ω. Test the center end of the plug with the multimeter RX 100Ω, open the microphone switch on the ON, the resistance should be 600Ω. If the impedance is not measured, it is explained that there is a circuit breaking phenomenon at the head of the plug switch, which can be detected by a multimeter.

First, the front cover is unscrewed, and the two ends of the lead extraction line are directly measured. If R is used, it is proved that the inner of the voice coil is open; if the R is about 600Ω, it is proved that the voice coil is good, and the fault is in the plug or the wire rope and the switch. The practice proves that the phenomenon of circuit breaking often occurs in these places : such as the screen cable capacity of the wire rope it is easy to break, the core wire is welded, the internal contact of the switch is bad, or the connection is desoldering.

( 3 ) Serious squealing is the common fault of the microphone, which is mainly caused by the following reasons. The shielded cable in the cord is broken off or the shield wire connected to the plug falls off, and only the core wire is normal. When the microphone plug is plugged into the socket of the amplifier, because the shielding line is broken, the grounding wire is also disconnected, and the human body induction or external interference of the hand microphone will be transmitted a self-excited oscillation in a loudspeaker. After replacing the sound head, because the core wire and the screen do line in the fine line are through the toggle switch, the two wiring terminals of the Ye to the sound head, so it is easy to cause the center line docking power amplifier the ground terminal screen of the device is connected with the input terminal of the power amplifier.

The microphone of the plastic cylinder shell is not found to be a problem, nor does it produce a howling, but the center line is connected to the metal case, the human body induction leads to the power amplifier, which produces the howling. Use the multimeter RX 100Ω to block the test. One end of the sound head is welded to avoid forming a circuit; then put the switch on the " ON " position. If placed in the " OFF " position, equivalent to the centerline and the shielding line short, will also form a circuit, affecting the test. Then use the multimeter to connect the center end of the plug and the microphone metal shell, should not be turned on, indicating that the core wire is not connected with the hand-held metal part, the utility model prevents the human body from sensing, and the metal cylinder shell is connected with the terminal of the plug shield wire, so that the grounding part of the power amplifier is held, there will be no howling.

 ( 4 ) To detect the light and distortion of the sound head, the front cover of the sound head is unscrewed to observe whether the vibration film is compressed and has no elasticity. Use the multimeter RX1 file, two stylus points on both ends of the touch head; if the sound is very small, use RX 100Ωto measure the impedance. If the impedance is about 300Ω, the inter-turn short circuit exists in the voice coil, which results in the decrease of electromagnetic induction. If there is an obvious " rustling " sound on the two terminals of the touch voice coil, it is the friction sound produced by the collision between the voice coil and the magnetic steel, indicating the change of the position of the voice coil or the vibrating membrane, can not be used. If the above parts are normal, generally magnetic steel magnetic decline, only the replacement of the sound head.

This article is from Allicdata Electronics Limited.