What gases can be detected by the four-in-one gas detector?
1. Four-in-one gas detector
I believe everyone knows that in the use of many gas detectors, because of the different detection gases, there are also many types of detectors. Among them, the four-in-one gas detector is a gas detector that many people will use at present. , because it can support us to detect gas at the same time. So which four gases are detected by the four-in-one gas detector?
The four-in-one gas detector detects four gases, as follows:
Combustible gas (LEL), oxygen (O2), carbon monoxide (CO), hydrogen sulfide (H2S)
Because these four gases are common gases produced during our production or operation, they have an impact on our life safety. The four-core one-gas detector is equipped with different gas sensors according to different gases, which is easy to maintain and is suitable for flammable and toxic gas leakage.
The four-in-one gas detector is a composite detector that can detect multiple gases and can display the numerical index of four gases or one gas at the same time. When a certain gas index to be detected is within the alarm range, the instrument will automatically perform a series of alarm actions, flashing light, vibration and sound.
Generally, it can be applied to enclosed and semi-enclosed spaces, as well as post-event safety inspections on fire house sites. There are many fields of application, such as petroleum, chemical industry, metallurgy, mining, fire protection, gas, environmental protection, electric power, communication, papermaking, printing and dyeing, grain storage, urban water supply, sewage treatment, food, scientific research, education, national defense and other fields. application.
2. Types of SMT detection technology
(1) Manual visual inspection is a method of detection with the naked eye. Its detection range is limited, and it can detect missing components, square polarity, correct model, bridging and partial solder joints. Because manual visual inspection is easily affected by human subjective factors, it has high instability. Manual visual inspection is even more difficult when dealing with 0603, 0402 and fine-pitch chips, especially when BGA components are used in large quantities, manual visual inspection is almost powerless to check the soldering quality.
(2) Flying probe test is a machine inspection method. It uses two probes to power up components to achieve detection. It can detect defects such as component failure and poor performance. This test method is relatively suitable for plug-in PCBs and low-density PCBs mounted with components above 0805. However, the miniaturization of components and the high density of products make the shortcomings of this detection method obvious. For 0402-level components, due to the small area of the solder joints, the probes cannot be connected accurately, especially for high-density consumer electronics products, the probes will not be able to touch the solder joints. In addition, it cannot accurately measure PCBs that use electrical connections such as parallel capacitors and resistors. Therefore, with the high density of products and the miniaturization of components, flying probe testing is used less and less in actual testing work.
(3) ICT bed of needles testing is a widely used testing technique. Its advantage is that the test speed is fast, and it is suitable for a single variety and a large number of products. However, with the enrichment of product varieties, the improvement of assembly density and the shortening of new product development cycle, its limitations are becoming more and more obvious. Its disadvantages are mainly manifested as: it is necessary to specially design test points and test molds, the production cycle is long, the price is expensive, and the programming time is long; the test difficulty and test inaccuracy caused by the miniaturization of components; after the design of the PCB is changed, the original test Molds will not be available.
(4) Automatic optical detection AO is a detection method that has emerged in recent years. It obtains images of components or PCBs through CCD photography, and then judges defects and failures through computer processing, analysis and comparison. Its advantages are: fast detection speed, short programming time, can be placed in different positions in the production line, easy to find faults and defects in time, and combine production and inspection into one. Therefore, it is a detection method that is widely used at present. But the AOl system also has deficiencies, such as the inability to detect circuit errors, and the detection of invisible solder joints is powerless.
(5) Functional test. ICT can effectively find various defects and failures that occur during the SMT assembly process, but it cannot evaluate the performance of the system composed of the entire PCB circuit board in terms of clock speed. The functional test can test whether the entire system can achieve the design goal. It regards the unit under test on the circuit board as a functional body, provides input signals to it, and detects output signals according to the design requirements of the functional body. This type of testing is to ensure that the board is functioning as designed. The simplest method of functional testing is: connect the special circuit board on an assembled electronic device to the appropriate circuit of the device, and then apply voltage. If the device works normally, it indicates that the circuit board is qualified. This method is simple and requires less investment, but it cannot automatically diagnose faults
