Depending on the capacity of the electrolytic capacitor, the multimeter's R×10, R×100, and R×1K blocks are usually used for testing and judgment. The red and black test leads are respectively connected to the negative pole of the capacitor (the capacitor needs to be discharged before each test), and the yaw of the hands is used to judge the quality of the capacitor.
1. If the hands are quickly swung to the right and then slowly retracted to the left, the capacitor is generally good.
2. If the needle does not turn after swinging, the capacitor has broken down.
3. If the hands are gradually returned to a certain position after the needle is placed, the capacitor has leaked.
4. If the hands are not placed, it indicates that the capacitor electrolyte has dried up and lost capacity.
Some leakage capacitors are not easy to accurately judge by the above method. When the withstand voltage of the capacitor is greater than the voltage value of the battery in the multimeter, according to the characteristics that the leakage current is small when the electrolytic capacitor is being charged and the leakage current is large during the reverse charging, the R×10K block can be used to reversely charge the capacitor. Whether the needle stays stable (ie, whether the reverse leakage current is constant), thereby judging the quality of the capacitor, and the accuracy is high.
The black pen is connected to the negative pole of the capacitor, the red pen is connected to the positive pole of the capacitor, the hands are quickly swung up, and then gradually retreat to somewhere to stay still, indicating that the capacitor is good, and the hand is unstable after a certain position or stays. The capacitor moving slowly to the right has leaked and cannot be used any more. The hands are typically stuck and stable over the 50 - 200K scale.
The so-called portable projector, also known as pocket projector, mainly through the 3M LCOS RGB three-color projector and decoding technology, the traditional huge projector is compact and portable, making the projection technology closer to life and entertainment.
Advantages compared with traditional projectors:
1. Small size, light weight, easy to carry.
2. Low calorific value and low noise.
3. The price is relatively cheap.
4. Most models support wireless connection through software projection.
Applicable fields:
1. Replace some functions of TV: some machines can have built-in CMMB function, or can be directly connected to the set-top box to put TV, which can be used as a 21-inch TV during the day and a 60-100-inch TV at night (Note: Because of lumen and resolution issues, lumens during the day If the degree is not enough, it must be projected at a close distance) to achieve the effect of home theater; it is convenient to move and break through the traditional film and television space. Even if you are on the mountain, you can also share today's TV series, movies, and MTV with your lover.
2. Business trip: Portable projectors are easy to carry because of their small size and light weight. When you need to display computer content or mobile phone content, you only need to connect the portable projector to achieve the demonstration effect.
3. Private space: For dormitory beds or small private spaces, in the absence of a computer, you can use a portable projector to project the content of your mobile phone to watch video pictures, etc., without staring at the mobile phone at close range.
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