How to test a microphone with a multimeter_How to identify the positive and negative poles of a microphone

　　A microphone is an energy conversion device that converts sound signals into electrical signals. It is a device that is exactly the opposite of a speaker (electric → acoustic). It is the two terminals of a sound device, the microphone is the input, and the speaker is the output. It is also called a microphone core, microphone, microphone, and microphone. This article mainly introduces how to identify the positive and negative poles of a microphone, and how to measure a microphone with a multimeter. First, let's understand the structure of a microphone.

　　Microphone structure

　　1. Dustproof net:

　　It protects the microphone, prevents dust from falling onto the diaphragm, prevents external objects from puncturing the diaphragm, and also has a short-term waterproof effect.

　　2. Shell

　　The supporting parts of the entire microphone, with other parts encapsulated in the outer casing, are the grounding point of the microphone and can also play a role in electromagnetic shielding.

　　3. Diaphragm

　　It is a main component for sound-to-electricity conversion. It is a stretched Teflon plastic film glued to a thin metal ring. The side of the film that contacts the metal ring is coated with a very thin metal layer. The film can be charged with electric charge and is also an electrode plate of a variable capacitor, and it is a vibrating plate.

　　4. Gasket:

　　The distance between the two plates of the supporting capacitor is left with a gap, providing a space for the diaphragm to vibrate, thereby changing the capacitance.

　　5. Plate:

　　The other electrode of the capacitor is connected to the G pole of the FET.

　　6. Polar ring:

　　Connect the plate to the G pole of the FET and provide support.

　　7. Cavity:

　　Fix the plate and the ring to prevent the plate and the ring from short-circuiting to the case (S and G poles of FET are short-circuited).

　　8. PCB assembly:

　　It is equipped with devices such as FET and capacitors, and also serves to fix other components.

　　9. PIN: Some microphones have PIN on the PCB, which can be soldered to other PCBs to connect to the front pole type. The back pole type is also slightly different in structure.

　　How to identify the positive and negative poles of a microphone

　　Look at the two tin points on the board. If they are independent, they are the positive pole. If the copper foil is connected to the outer shell, it is the negative pole. Or use a multimeter to measure the conductivity. One of the tin points and the outer shell are connected together.

　　How to test microphone with multimeter

　　Condenser labels are generally electret type, and the basic structure is shown in the figure below.

　　1. A normal electret can be tested with a multimeter. The general model directly measures the resistance value around 2K. If you blow or knock on it, you can see a significant change in resistance.

　　2. If it is a digital multimeter, connect the red test lead to the positive pole of the electret and the black one to the negative pole (usually the leg connected to the shell). The conventional model 2k resistance is good, and the change in blowing and knocking is generally greater than 500 ohms. The greater the change, the better the sensitivity.

　　3. If you use a pointer multimeter, select the right gear, connect the black test lead to the negative pole of the electret, and the red one to the positive pole. The test method is the same.

　　The above can only test the sensitivity and the general quality, but cannot determine other parameters, such as distortion and noise.