CRT Monitors Information
CRT monitors are ruggedized for use in control room, factory floor, or process applications. CRT stands for cathode ray tube. A CRT is essentially a sealed glass bottle with no air inside. It begins with a slim neck and tapers outward until it forms a large base. The base is the monitor's "screen" and is coated on the inside with a matrix of thousands of tiny phosphor dots.
Important display specifications to consider when searching for CRT monitors include:
- image resolution
- vertical scanning frequency
The diagonal is the measurement from one corner to the corner diagonally across from it. Common diagonals include 10 in., 12 in., 14 in., 15 in., 17 in., 19 in., 21 in., and 23 in. Image resolution is a measure of how sharp the image will appear on the screen; the higher the resolution, the sharper the image. The vertical scanning frequency, or refresh rate, is the rate at which each pixel on a screen is re-drawn. A low refresh rate results in an image that flickers, resulting in eyestrain. The standard for flicker-free images is 85Hz. CRT monitors can be supplied in color or monochrome. The range of colors is generated with varying combinations of different discrete colors. One common technique is sensing the red, green, and blue components (RGB) and combining them to create a wide spectrum of colors. A monochrome monitor has an image that is presented in black, white, and grayscale.
Important physical specifications to consider when searching for CRT monitors include:
- user controls
- external connections
Mounting options for CRT monitors include panel mount, chassis mount, rack mount, and desktop. User controls include front panel, rear panel, and on-screen display. Common external connections include serial interfaces, parallel interfaces, USB, SCSI, and mouse port. Technology choices for CRT monitors include shadow mask, aperture grille, and enhanced dot pitch. A shadow mask is a fine metal sheet containing holes that correspond with the tube's phosphor dots. As the electron beam passes through these holes, it becomes slightly narrower and is guided more accurately toward its target phosphor. An aperture grille is made up of fine strips of metal that are strung at high tension across the inside of the tube. The phosphor lines have no horizontal breaks. The aperture grill design attributes allow a greater amount of the electron beam through, resulting in a brighter picture. The strips run from top to bottom, so the tube can be flat vertically, reducing glare and image distortion. Enhanced dot pitch (EDP) concentrates more on the phosphor implementation. The distance between the phosphor dots on the horizontal has been reduced, and the dots have been elongated so they are oval rather than round.
Common features found on CRT monitors include flat screen, touch screen, anti-reflective coating, non-interlaced, industrial metal cabinet, and digital video input signal. The monitor can have a (nearly) flat screen as opposed to a curved screen typical of most CRT monitors. A touch screen is a user-friendly device; the user touches the screen and the input is communicated directly to the computer. An anti-reflective coating is a specialized coating used to reduce glare. Non-interlaced (NI) is where the electron beam draws every line before returning to the top for the next frame, resulting in a far steadier display. Industrial metal cabinets provide protection from harsh industrial environments. Some monitors can accept digital video input signals. An important environmental parameter to consider when searching for CRT monitors is the operating temperature.
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