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CTA-412

Revision A, December 2004

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Electrical Performance Standards for Direct View High Resolution Monochrome Closed Television Monitors



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Description / Abstract:

The Electrical Performance Standards for Direct View High Resolution Monochrome Closed Circuit Television Monitors given here represent, it is believed, the best agreement between the members of the Closed Circuit Television Committee, who drafted these Standards, consistent with the rapidly developing state-of-the-art.

Committee TR-17 has undertaken the development of Electrical Performance Standards for Direct View High Resolution Monochrome Closed Circuit Television Monitors to define significant parameters descriptive of operation of these devices and to outline minimum levels of performance deemed desirable to develop an acceptable display. This effort will promote interchangeability of the products of different manufacturers, thereby eliminating confusion on the level of performance that can be expected from an appropriately specified device. It will assist the purchaser in selecting and obtaining the proper product for a particular need. The lack of a previous standard for high resolution closed circuit television monitors justified this work.

The Standards consist of (1) Definitions, (2) Standards, and (3) Suggested Methods of Measurements, for those parameters believed to be importance.

These Standards are intended to apply only to Direct View High Resolution Monochrome Closed Circuit Television Monitors with a video input; that is, signals generated at a nearby point where control can be exercised over picture quality. They are intended to apply with a video signal as described by EIA Standard RS-343A, "Electrical Performance Standards for High Resolution Monochrome Closed Circuit Television Camera," latest revision thereof.

Standard Measurement Conditions

Measurement of signal levels shall be made in accordance with IEEE Standard 205-1958, Reaffirmed 1972, or latest revision thereof, on Television; Measurement of Luminance Signal Levels except that the frequency response filters shall not be used. This standard defines the levels of a television video signal in terms of IRE Units. Reference white level is +100 IRE Units, blanking level is 0 IRE Units, and sync tip level is −40 IRE Units. Thus the peak-to-peak level of a composite video signal extending from sync tip to level to white level is 140 IRE Units.

Unless otherwise specified, all monitor measurements shall be made with a composite video signal input, sync negative, having a nominal level of one volt peak-to-peak (140 IRE Units). The sync signal shall have a nominal amplitude of 0.286 volt, (40 IRE Units), and the picture signal with setup, as measured from blanking level to reference white level, shall have a nominal amplitude of 0.714 volt (100 IRE Units). The nominal value of set-up shall be 0.054 volt (7.5 IRE Units).

The input signal shall be fed to the monitor by means of a 75 ohm coaxial cable terminated at the monitor with 75 ohms. The source impedance of the equipment feeding the monitor shall also be 75 ohms.

Initially the monitor shall be set-up using an electronically generated composite test signal. The picture signal may be a white window, staircase or multiburst with white reference. The APL (average picture level) should be 60% or less and the applied composite video voltage should have a standard level of 1.0 volt (140 IRE Units).

The window signal to be used in specific tests within this standard shall generate a displayed rectangle having a 4:3 aspect ratio and a equal to nominally 20% of the normal active raster area and be capable of being positioned as required on the monitor screen.

The active raster area shall be the complete unblanked area, regardless of that portion which may be obscured by the mask or display tube edges.

If provisions are included to either switch or rewire the monitor for normal scan/underscan operation, the monitor shall be operated in the normal scan mode. If the monitor includes a switch for dc Restoration "ON-OFF", it shall be operated in the "ON" mode. The set-up controls and adjustments such as focus, centering, scan size, and scan linearity, should be adjusted to their optimum positions. The aspect ratio, relating width to height, of the active scanned area should be 4:3. By means of the contrast and brightness controls the black reference in the video signal should be set to subjective black, and the white reference set to the manufacturer's rated maximum luminance. The highlight areas on the CRT should be observed to determine that the TV scan lines are visible. This insures that the CRT is not being over driven causing CRT spot blooming. To accommodate for variations in black level subjective black may be re-established by adjusting the brightness control only when switching to test signals of different APL's. The input line voltage shall have a nominal value of 120 volts 60 Hz.

Certain tests such as Maximum Luminance, Interlace, Luminance Stability, Low Frequency Response, Gray Scale and Contrast Ratio, Horizontal Resolution, Mid-Frequency Response, Transient Response, and Raster Modulation are made by means of a luminance meter or a TV camera focused on the monitor CRT faceplate. For these tests the ambient light falling on the CRT bonded faceplate or the protective glass cover in front of the CRT faceplate should be 0.1 foot-candle or less.

Measurements of Low Frequency Response, Mid-Frequency Response, Luminance Stability and Raster Modulation, call for displays in which the white areas are displayed at approximately 50% of the rated maximum luminance of the monitor. In all these cases the composite input video signal shall have a standard sync level of 0.286 volt (40 IRE Units). The portion of the composite video input signal as measured between blanking level and white level shall be adjusted to have a value of 0.5 volt (70 IRE Units). This insures that the setting of the contrast and brightness controls will provide correct interstage video voltages and bias on the CRT. The portion of the composite video input signal between blanking level and white level is set to 0.5 volt (70 IRE Units) instead of 0.36 volt (50 IRE Units) because of the non-linear transfer characteristic of the monitor CRT.

The monitor shall meet all performance specifications over the specified temperature range with only the adjustment of external controls.

Certain test require the use of a calibrated foot-lambert meter. This meter should have an acceptance angle such that it measures only the specified are without spill over from the surrounding area.