1 judge phase line and neutral line
On low-voltage distribution lines, especially the indoor wiring of buildings, dark wires are often required to be laid through pipes for the sake of indoor beauty and durability. In the process of laying, it is sometimes necessary to find which is the phase line and which is the neutral line. Using a multimeter, you can easily judge the phase line and neutral line (you can scan QR code to learn).
(1) Contact measurement
① Judge with pointer multimeter
As shown in Figure 20-1, place the multimeter in the AC voltage "250V" or "500V" gear, wrap the black probe wire for several times, hold it tightly with your hand (do not touch the metal part of the probe), and touch the two sockets (or the exposed parts of the two wires) on the power socket with the tip of the red probe in turn. One time when the probe deflects to the right, the red probe touches the phase line and the other time is the neutral line.
For example, using dt9808 digital multimeter, turn the change-over switch to the "2V" AC voltage (ACV) gear, and judge which of the two plastic wires of the energized line is the phase line.
The specific method is as follows: first separate the measured ends of the two wires by 2 ~ 3cm, and then contact the outer skin of the other wire with the tip of the red watch pen. The display value is 0.846v. Therefore, it can be judged that the conductor with the measured voltage of 0.846v is the phase line, and the conductor with the lower measured voltage is the neutral line.
2 judge the broken core position of wire (or cable)
The conductor or cable will be heated and aged due to electrodynamic effect or thermal effect, which will cause damage or even fracture of conductor or cable core. Generally, it is impossible to find the broken part without stripping the insulation. A multimeter can be used to accurately and conveniently judge the broken parts of insulated wires or cables, and then repair the damaged parts for continued use. Judge the test wiring as shown in figure 20-4 (two-dimensional code can be scanned for learning).
Test Leads For Multimeter
Usually, when we do maintenance, we use the inspection pen we often carry to judge whether the low-voltage wires and equipment have electricity. When I work outside one day, I happen to have a broken or forgotten pencil. I have to judge whether the equipment has electricity and the color of the wire is the same, and how to judge whether it is a zero wire and a live wire, and what to do with only a multimeter on hand.
When measuring DC voltage with a multimeter, it is easy to tell which wire is positive and which is negative. When measuring AC, you can only read out the voltage, but not the zero wire and live wire:
In fact, as long as we understand the characteristics of the multimeter, we can simply judge the zero fire line.
Use the mf47 pointer multimeter as a demonstration. First, select the gear knob switch to the Ac500V gear, and gently press one finger on the black pen metal needle (the tighter the finger presses the probe, the higher the reading). Maximum reading
It's the live line. There's no reading on the zero line. Sometimes the reason for the difference in measurement is that the largest reading is the live line, the second is the zero line, and the smallest is the ground line.
Test Leads For Multimeter
There are many interfaces in the audio and video field. As a very common video and audio transmission interface, it has its own advantages in equipment transmission.
1. BNC connector
Coaxial Cable Adapter, BNC Male/RCA Female
Coaxial Cable Adapter, BNC Female/F Male
The BNC connector is different from the special display interface of the ordinary 15-pin D-SUB standard connector. It consists of RGB three primary color signals and five independent signal connectors for line synchronization and field synchronization. It is mainly used to connect workstations and other systems that require high scanning frequency. The BNC connector can isolate the video input signal, so that the interference between the signals is reduced and the signal bandwidth is larger than that of the ordinary D-SUB, which can achieve the best signal response effect.
2. RCA connector
RG59A coaxial cable, RCA male/BNC male
3-wire RCA audio/video cable, RCA male/male
The RCA connector is by far the most common audio/video terminal, commonly known as the lotus socket. It is not specifically designed for any kind of interface, it can be used for both audio and ordinary video signals.
The RCA terminal adopts the method of coaxial transmission of signals, the central axis is used to transmit signals, and the contact layer around the outer edge is used for grounding, which can be used to transmit digital audio signals and analog video signals. RCA audio terminals are generally marked in pairs with different colors: red for the right channel and black or white for the left channel. In some cases, the center and surround channel cables are color-coded to facilitate wiring distinction, but all RCA connectors throughout the system are electrically identical. Generally speaking, RCA stereo audio cables are a group of left and right channels, and each channel is a line in appearance.
3. The advantages of both
The main function of the BNC interface is to transmit video signals, and the RCA interface mainly transmits audio signals. Different interfaces have different advantages and functions. For example, the BNC connector can reduce the interference between video signals and achieve the best signal response effec
Video game cables
As technology has advanced, so have the cables required for equipment. Even though many manufacturers are moving to wireless solutions, you may still need some form of cable at all times. This is especially true for video equipment. TVs, monitors, and peripherals require a variety of cables and connections to function properly. So, what's the difference between them and which ones do you need? Let's take a look at some of the most popular types of video cables and when you need to use each.
VGA stands for Video Graphics Array. The connection was developed by IBM in 1987, making it one of the oldest video connections still in use today. It is widely used in video cards, televisions, computer monitors and laptops. VGA can support a maximum resolution of 640x480 with 16 colors, although you can increase the color to 256 by lowering the resolution to 320x200. This is called mode 13h and is usually used when booting the computer into safe mode. Mode 13h was frequently used in video games in the late 1980s. VGA is capable of transmitting RBGHV video signals, including red, blue, green, horizontal sync and vertical sync. The iconic blue adapter has screws on both sides to secure the connection. The socket consists of 15 pins arranged in three rows of five. It's since been surpassed by digital connections like HDMI and DVI, but it's still popular thanks to the rise of nostalgic gaming and its inclusion in cheap monitors and monitors.
RCA leads are one of the most intuitive video cables. Red, white and yellow plugs are synonymous with audiovisual equipment produced in the 1990s and early 2000s. It's also the primary connection for many consoles, including the Nintendo Wii. Most TVs no longer support RCA inputs.
The Digital Display Interface Working Group introduced the Digital Visual Interface (DVI) in 1999, the successor to the VGA cable. A DVI connection can transmit uncompressed digital video in one of three different modes: DVI-I (integrated) combines digital and analog in the same connector.
DVI-D (Digital) only supports digital signals.
DVI-A (analog) only supports analog.
DVI-I and DVI-D can be in sin