Monitor manufacturers generally adopt the following four display modes: 1. Digital tube (LED display): the display content is single, only numbers can be displayed, but waveform information cannot be displayed, and the function is simple. Early single-parameter monitors all adopted digital tube. 2. CRT display: a very common display, which has the advantages of high resolution and low price, but has the disadvantages of large size, difficult miniaturization of the whole machine, high-voltage radiation and easy heating. Iii. LCD display: LCD screen. Its advantages are small size, low power consumption, no radiation and no heat. In the mid-1990s, the advent of color TFT technology overcame the shortcomings of low brightness and small viewing angle of monochrome LCD. Because color display is pleasing to the eye and intuitive, it is widely used in daily life. At present, mainstream monitors at home and abroad all use LCD display. EL display screen: before the appearance of TFT display, EL display screen was once used for high-grade monitors. besides the advantages of LCD, it also has the advantages of high brightness and large viewing angle, with the disadvantage of high cost. Therefore, with the development of TFT display, the application of EL display in monitoring field is gradually being replaced by TFT display.