The author introduces an electronic instrument for detecting earthquakes and automotive tires, cold storage, air conditioners, refrigerator refrigerant leakage. Using the instrument to detect the leaflet leak, do not use eye observation, only the ear is listening to whether there is a leakage and the size of the sound, it can accurately determine whether there is a leakage and leakage, and can also detect the leak of the car tire and tap water pipeline. Also suitable for use in the earthquake disaster area.
The inspector uses the multi-pole amplifier circuit, through the detection probe M of the instrument, leaks the spurt of the spill, and enlarges to drive the headphones, so that people can listen to the "silk" sound, The purpose of accurate determination of the leakage site can be achieved by the sound. Its circuit formation is shown in the figure.
Teamwork and requirements
M leak detection probe uses a normal resident microphone to convert a weak leak sound wave signal into an electrical signal, output from the residential microphone to VT1, VT2 two-pole blocking coupling amplifier, R4 is the automatic gain control resistance, in practice, is actually a series current Negative feedback resistance, its existence, makes the large signal in distortion, and the audio power is enlarged by A1, LM386, and finally drive the headset. This circuit can only be listened with high-resistance headphones due to the limit of the number of circuit amplified levels (multiple).
In order to prevent the power supply from interference detection, the device does not have to be used, and the GP27A-L5 12V alkaline battery for motorcycle anti-theft alarm is powered. The battery is small and the life is long.
This power supply method can be completely eliminated to eliminate interference of AC noise. The power switch SA is switched with a miniature button. The full instrument is only the size of the cigarette case, can be released, carrying very convenient, especially the repair master of the on-site service.
A headphone socket and a residential microphone socket are provided on the outer casing. The detection signal acquired by the resident microphone M probe passes through the shield line to the microphone socket of the instrument, and the shield line length is 3m to 10m, or it can be determined according to actual needs.
Electronic component selection
R1 ~ R7 uses a 1/4 W metal film or a carbon film resistance. C1, C3, C5, and C6 select a non-polar porcelain interval capacitor. C2, C4, C7 selected pressure 16V high quality electrolytic capacitance. VT1, V12 can be used with 2SC9014 (or 3DX6) low noise front tubes. RP uses the winding resistance and the power is 1 / 2W. The A1 uses the LM386 audio power to enlarge the integrated block. The M resident microphone is used as a GRZ2-30. Because the leveling field effect tube in the resident microphone is enlarged, it has the advantages of high sensitivity, frequent frequency sound. CZ is the headphone output jack, there is no special requirements. Generally, the alignment of the alignment value is performed in the figure in the figure.
Making debugging and use
The VT1 and VT2 triodes in the figure are mounted on the circuit board, and the regulation of R2 causes the collector current of the VT1 to be about 0.45 mA, and the regulation of R5 causes the collector current of the VT2 to be about 1.25 mA. The R1 needs to be adjusted due to different polarization voltages required for the resident microphone. Adjust the R1 size until the sound heard in the headset is not distorted and the volume is appropriate.
When checking, it should be carried out in a quiet environment, and the leakage site is determined by the sound size measured by the mobile probe. Since this circuit is particularly sensitive to the sound, you should pay attention to the operation. In order to prevent audio feedback and external interference, the headphones must be clamped, when adjusting the volume and opening, the power source, should take the headset in advance. Wear / pick the headphones to move quickly, and the probe does not touch the object to prevent strong sound from the eardrum.
The on-site practice proves that this sound check is used to achieve the purpose of the refrigerator, air conditioner, and the detection of underground water pipes. It is a novel, efficient, convenient and safe electronic testing means. The instrument can also be used to check the freezer, cold storage and central air conditioning refrigeration systems, and can also check the gas pipelines and the ventilation of automotive tires.
Author: Sun Yong
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