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Stethoscope microphone



Stethoscope microphone

Along with narrow and wired remote microphones, there are devices that record vibrational vibrations of walls, ceilings, stacks, ventilation shafts, etc. These devices are called stethoscope microphones. They are quite complicated . Therefore, an apparatus is described below , which can serve as a prototype of a stethoscope microphone , and the principle of its operation. The circuit diagram of the device is shown in Fig. 2.45. The amplifier of audio frequency is assembled on a DA 1 chip of type K140UD6. Resistors R 1 and R 2 specify the operating mode of the microcircuit. The gain is determined by the value of the resistance of the resistor R 3. Transistors VT 1 of the type KT315 and UT2 of the KT361 type are connected by the emitter follower circuit and amplify the current output signal . The load of the amplifier is provided by the headphones TZN-2. The vibration sensor is made from a piezoceramic head 81, removed from an old turntable. Vibration is converted by a piezoelectric transducer into electrical ones and amplified by an DA 1 amplifier . As a piezoelectric transducer В2 , can a piezo - emitter of the type ЗП - i , ЗП-2 be used? and like them from electronic watches and toys. They reproduce frequencies in the range of 800-3000 Hz, which basically covers the speech frequency range. If necessary, you can amplify the signal to the desired level. value, using an additional audio amplifier . The signal to it comes from the output of the operational amplifier DA 1. Such a sensor can be successfully used as an alarm sensor. As a piezoelectric sensor B 1 , for example, PE-1, GZP-308 and others can be used.