A sound sensitive sensor is a type of sensor used for flow detection, which can be set with power when wired and operated in high/low sensitivity range mode. The high sensitivity range is suitable for long and short wave signals fluctuating at 40dB. The low sensitivity range is applied to long and short wave signals fluctuating between 28db and 68db. The sound sensitive sensor can operate independently of the control device by providing an external power supply.
1, The working principle of sound sensitive sensors
A sound sensitive sensor is a built-in capacitive electret microphone that is sensitive to sound. Electret microphones are mainly composed of two parts - the acoustic electric conversion part and the impedance part. The key component of acoustic electric conversion is the polarizer diaphragm. It is a very thin plastic film with a layer of pure gold film evaporated on one side. Then, after being polarized by a high-voltage electric field, opposite charges are respectively stationed on both sides. The evaporated gold surface of the membrane is facing outward and connected to the metal shell.
The other side of the membrane is separated from the metal plate by a thin insulating liner. In this way, a capacitor is formed between the evaporated gold film and the metal electrode plate. When the polarizing film encounters sound wave vibration, it causes a change in the electric field at both ends of the capacitor, resulting in an alternating voltage that varies with the sound wave. The capacitance between the polarizing film and the metal plate is relatively small. Therefore, its output impedance value is very high, about tens of megaohms or more. Such a high impedance cannot be directly matched with an audio amplifier. So, a junction field-effect transistor is inserted into the microphone for impedance transformation.
2, Application fields of sound sensitive sensors
The sound sensitive sensor comes with an analog output for use with Sitrans control devices. This sensor can operate independently of the control device by providing an external power source. Its output signal is sent to the control panel, chart recorder, data recorder, or programmable logic controller with appropriate inputs. Mainly used for solid flow detection. At the same time, the device can also be used for detecting water pump cavitation and liquid leakage, and then generate sufficient sound alarms.