Refrigerator \ cold storage \ air conditioning refrigerant leak detector, Leak Detection
Keywords: refrigerator \ cold storage \ air conditioning refrigerant leak detector
Refrigerator \ cold storage \ air conditioning refrigerant leak detector
When the cold storage, air conditioner, refrigerator refrigeration system has occurred, sometimes even if the system operates normally, there is still a case where the cooling effect is increasing, and the detection difficulty of refrigerant leaks is quite, sometimes inspected (such as air conditioning) ), Even if you are floating on site, the operation is very inconvenient. Therefore, in the pre-sales, after-sales service, this test problem is urgently waiting.
The author introduces a portable electronic instrument for detecting cold storage, air conditioning, refrigerator refrigerant. Using this instrument to detect the refrigerant leak, only the headset is listening to the leakage like a doctor, it can accurately determine whether there is a leakage and leakage. In addition, leaks at tap water pipes can also be detected.
The detector uses a multi-stage amplifying circuit. Through the detection probe M of the instrument, use the ordinary headset to hear the very weak airflow or liquid, water flow, etc. of the leak, and the circuit composition is shown in the drawing. Show.
First, the principle of working
The leak detection probe M uses a normal electret microphone to convert a weak leak sound wave signal into an electrical signal, and the sound is passed from the microphone. After the VT1, VT2 two-stage blocking coupling is large, R4 is the automatic gain control resistance, actually a series The current is negative feedback resistor, and its presence makes the large signal fail, but also enlarges by A1 (LM1386) audio power, and finally drive the headset. This circuit uses high-resistance ear machine to listen, on the one hand, can reduce the number of amplifier, on the other hand, can isolate the interference of the external sound, and pay attention to the listening of the leak.
In order to prevent the power supply from the test interference, the device does not have a general AC power booster rectification to obtain a power supply, and a special battery (GP27A-L5 12V alkaline battery) with a motorcycle anti-theft alarm is used, and the battery is small. long lasting.
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 instrument is only the size of the cigarette case, which can be placed in the bag, which is very convenient, especially suitable for home repair.
The detection signal acquired by the electret microphone M probe is connected to the microphone socket of the instrument through the shield line, and the shield line is about 3m long, or it can be determined according to actual needs.
Second, the selection of components
R1 ~ R7: Use a 1/4 W metal film or a carbon film resistance. C1, C3, C5, C6: Select a non-polar paper dielectric capacitor. C2, C4, C7 selected pressure 16V high quality electrolytic capacitance. VT1, VW2 can be used with 2SC9014 low noise tubes. RP is selected with an L / 2W potentiometer. The A1 uses LM1386 audio power to enlarge the integrated block. The electret microphone adopts GRZ2-30. Because there is a first-level field effect tube in the elective microphone, it has the advantages of high sensitivity and good frequency sound. CZ is the headphone output jack, there is no special requirements.
Third, debugging and use
After the assembly is completed, the R2 adjusts R2 to the collector current of the VT1 at about 0.45 mA, and the adjustment R5 causes the collector current of the VT2 to be about 1.25 mA. Due to different polarization voltages required for the electret microphone, adjust the R1 size until the sound is not distortion in the headset, and the volume is appropriate.
When checking, it is best to perform in a quiet environment, determine the leakage site by the sound size measured by the mobile probe. Since this circuit is particularly sensitive to the sound, it is fine to operate. 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. In particular, it should be noted that the probe does not rub the object when the operation is to prevent strong tone, and the diaphragm is unfavorable. It has been proved to practice on site, it is a novel, efficient, convenient, safe electronic testing means. In addition to the detection of the room air conditioner, it can also be used to measure the refrigerator, freezer, cold storage and central air-conditioning system, and also measuring the water leakage of water floating pipelines, and detect gas pipelines.
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