麦克风的原理

麦克风的原理 Structure and characteristics? The internal structure of the electret microphone is shown in figure 1 (a), which consists mainly of "acoustic - electricity" conversion and impedance transformation. "Sound - electricity" transformation of key components is electret diaphragm vibration, it is a very thin plastic film as a substrate, on the one side evaporation a layer of pure metal film, and then after dealing with the high voltage electric field "in", formed in the two sides can maintain the long-term opposite charges - which is "electret" (also known as "permanent charge body") the origin of the word. The metal membrane of the vibrating diaphragm is facing outward and is connected to the metal casing of the microphone. The other side is near a metal plate with a stomata, which is separated by a thin plastic insulation washer. In this way, the vibrating diaphragm and metal plate is formed between a itself has a capacitance electrostatic field - visible electret microphone in fact is a kind of special, no external polarization voltage capacitor microphone. The metal plate is connected to the grid of the special field effector, and the source of the field effector S and the drain D as the receiver of the microphone. In this case, with the metal case, there are three electrode in the body, which is shown in figure 1 (b). If the source S (or the drain D) of the field tube is connected to the metal case, the receiver is left with two electrodes. ? ???? The internal structure of the electret microphone is shown in figure 1 (a), which consists mainly of "acoustic - electricity" conversion and impedance transformation. "Sound - electricity" transformation of key components is electret diaphragm vibration, it is a very thin plastic film as a substrate, on the one side evaporation a layer of pure metal film, and then after dealing with the high voltage electric field "in", formed in the two sides can maintain the long-term opposite charges - which is "electret" (also known as "permanent charge body") the origin of the word. The metal membrane of the vibrating diaphragm is facing outward and is connected to the metal casing of the microphone. The other side is near a metal plate with a stomata, which is separated by a thin plastic insulation washer. In this way, the vibrating diaphragm and metal plate is formed between a itself has a capacitance electrostatic field - visible electret microphone in fact is a kind of special, no external polarization voltage capacitor microphone. The metal plate is connected to the grid of the special field effector, and the source of the field effector S and the drain D as the receiver of the microphone. In this case, with the metal case, there are three electrode in the body, which is shown in figure 1 (b). If the source S (or the drain D) of the field tube is connected to the metal case, the receiver is left with two electrodes. ?? ? The presence of the microphone in the polar body is made up of the structure of the microphones. Figure 1? ??????????? ??????????????? ? The end of the day is the last day of the year. (a)? Internal structure???????????????????????????????????????? (b)? Internal circuit? Hall of fame: celebrities bring you to feel their driving life. ??????????????????? ???? Electret microphone works like this: when the electret diaphragm acoustic vibration, can cause with the change of the distance between the metal plates, namely electret diaphragm vibration and metal plate between the capacitance change as sound waves, resulting in both ends of capacitance inherent in the electric field changes (U = Q/C), changes over sound waves are produced by alternating voltage. Because the electret diaphragm and metal plate formed by the capacitance between the relatively small capacity (generally for dozens of wave method), and its output impedance values (XC = 1/2 PI fC) is very high, about more than decades megohm. Such a high impedance is not directly with the general audio amplifier at matching the input, so in the microphone access a junction field-effect transistor for impedance transformation. Field effect tube with very high input impedance will of voltage on both ends of the "capacity", and at the same time of amplification, get and sound waves corresponding to the output voltage signal. ????? The field effect tube inside the microphone is a low noise special tube, The compound of its grid G and the source polar S has a diode VD, as shown in figure 1 (b), which mainly ACTS as a "anti-blocking" effect. Must work well in the right of the field effect tube under dc voltage, so the electret microphone belongs to the active device, namely must give electret microphone when using combined with appropriate dc bias voltage, to ensure that its normal work, this is different from the ordinary moving-coil microphone, piezoelectric ceramics. ? What are the shapes and types? It is commonly used in the form of the microphone, which is used in the microphones. The machine is suitable for installation in all kinds of electronic devices, as shown in figure 2 (a). The most common type of machine is cylindrical, with a diameter of phi 6mm, phi 9.7 mm, phi 10mm, phi 10.5 mm, phi 11.5 mm, phi 12mm, phi 13mm. A variety of specifications; Pin electrode is count points at both ends and three type two kinds, pin form can be directly welded on the circuit board inserted into type, with soft shielding wire lead type and without lead leg type 3 kinds. If size is classified, there are common type and miniature. Based on type MF50 pointer multimeter, for example, introduced under the condition of amateur use multimeter to quickly determine the polarity of the electret microphone and detect the stand or fall of electret microphone and the performance of the concrete method. ? The detection of the microphone in the polar body. Figure 1? In the United States of China??????????? ???????????????????????????????????????????????????????????????????????????????????? (a) to judge polarity and good? In the end of the year. ???????????????????????????????????????????????????????????????????????????????????? (b) check the sensitivity of the microphone at both ends? In the end of the year.??????????????????????????? ?????????????????????????????????????????????????????????????????????????????????????????? (c) detect the sensitivity of the three-terminal microphone. ?? Determine polarity - the electret microphone internal field effect tube drain and source D S lead electrode directly as the phone, so just judge the drain and source D S, also is easy to determine the electrode of the electret microphone. As shown in figure 1 (a), the multimeter is set to "R * 100" or "R * 1k", and the black marker picks up any pole, and the red marker picks up the other pole and reads the number of resistors. Two pens and, after reading resistance number again, and compare the two measurements, a smaller resistance, black pens and meet for the source S, red pens and get close to drain D. Further: if the metal shell of electret microphone and detected by the electrode is connected to the source S, then tested the receiver should be on both ends of the electret microphone, the drain electrode D shall be the "power/signal output foot", the source S electricity is "grounding pin"; If the metal case of the microphone is connected to the drain D, then the source S electrode should be. "Negative power/signal output foot", the drain electrode is extremely "grounding". If the receiver of the metal shell to be measured and the source and drain electrode D S are interlinked, three-terminal type electret microphone, the drain and source D S electrodes respectively as "positive power supply pin" and "signal output foot" (or "signal output foot" and "negative" power supply pin), metal shell is "grounding pin". ? For good or bad - in the above measurements, the normal resistance value of the microphone should be a small amount. If the positive and reverse resistance values are infinite, then the field effect tube inside the microphone is opened. If the positive and reverse resistance are close to or equal to 0 Ω, then tested the microphone inside the field effect tube has been breakdown or short circuit happened; If positive and reverse resistance values are equal, the crystal diode between the field effect tube grid and the source polar S has been cleared. Because the microphone in the pole is a one-time pressure seal, the internal failure is usually unable to repair and replace the old one. ? The detection sensitivity, the multimeter to x 100 "R" or "R x 1 k" electric block, as shown in figure 1 (b), black pens and (multimeter internal battery anode) after being measured both ends of the electret microphone drain D, Red pens and connect the grounding end (or red pens and pick up the source S, black pens and connect the grounding end), the multimeter pointer indicating on a scale, with a mouth positive rusheng hole breathed into the mouthpiece, multimeter pointer should be larger. The larger the motion of the needle, the higher the sensitivity of the receiver. If no response or response is not obvious, the microphone has been damaged or degraded. For three-terminal type electret microphone, as shown in figure 1 (c), black pens and still pick up the phone to be tested drain D, red pens and connected to the same source S and grounding terminal (metal shell), then testing can be blowing in the same way. ? ???? The above detection method for the loading type electret microphone, external type with lead plug on electret microphone, can be directly on the plug as shown in figure 2 is measured. But beware, some switch mounted ON the microphone, test to the switch to "ON" position (ON), and is not able to switch to "OFF" (OFF) position. Otherwise, normal testing will not be possible. ? ? ? 1234567890 abcdefghijklmnabcdefghijklmn! @ # $% ^ & * () _ +. The two pick up lu, 13579. Sapphire case yuan evening or spend the night dongfeng more blows the star like BMW carving car fragrance full road chicken sound moving horse-ray turn, night fish dragon dance moth son hoary willow gold wisp of accomplished with fragrance to he found thousands of baidu may look back that person but in the lights dim You might like