1、c -1 1 .- EIA 493 82 M 3234b00 0071491 4 ANSI/EIA RS-493 - 1982 APPROVED JUNE 28, 1982 EIA STANDARD RECOMMENDED PRACTICE FOR CONVERSION OF U.S. TO METRIC DIMENSIONS FOR COLOR AND MONOCHROME CATHODE RAY TUBES AND THEIR COMPONENT PARTS RS-493 JUNE 1982 Engineering Department ELECTRONIC INDUSTRIES ASSO
2、CIATION -. . .- . I. - - - _- -. EIA 493 82 M 3234600 007l1492 b M ,:. .: -_ .- . -. NOTICE ng Standards and Publications are designed to serve the public gh eliminating misunderstandings between manufacturers and purchasers, facilitating interchangeability and improvement of products, and assisting
3、 the purchaser in selecting and obtaining wth minimum delay the proper product for his particular need. Existence of such Standards end Pub- lications shall oat in any respect preclude any member or non-member of EIA from manufactrirlg or selling products not conforming to such Standards and Publica
4、tions, nor shall the existence of such Standards and Publications preclude their voluntary use by those other than EIA members, whether the standard is to be used ei.t6er . - ._ domestically or internationally. Recommended Standards and Publications are adopted by EIA without regard to whether or no
5、t their adoption may involve patents on articles, materials, or processes. By such actim, EIA does not assume any liability to any patent owner, nor does it assume any obligation whatever to parties adopting the Recom- mended Standard or Publication. This Standard is based upon the technical content
6、 of International Electro- technical Commission, (or International Standardization Organization) recom- mendation 191-1, “Mechanical Standardization of semiconductor Devices, 1966. It conforms in all essential respetcts with the IEC (or ISO) recommendation. Published by ELECTRONIC INDUSTRIES ASSOCIA
7、TION Engineering Department 2001 Eye Street, N.W. Washington, D.C. 20006 Copyright 1982 ELECTRONIC INDUSTRIES ASSOCIATION All rights reserved PRICE: .$4.00 . Printed in U.S.A. , - _ EIA 473 82 m 3234600 0071473 B m RS-493 RECOMMENDED PRACTICE FOR CONVERSION OF U.S. TO METRIC DIMENSIONS FOR COLOR AND
8、 MONOCHROME CATHODE RAY TUBES AND THEIR COMPONENT PARTS FOREWORD The conversion procedures detailed in this EIA Recommended Standard were prepared under the cognizance of the. EIA JT-6 Committee on Television Picture Tubes and approved by the Tube Engineering Panel Advisory Council (TEPAC). This Sta
9、ndard is to be used as a guide for conversion from U.S. to metric dimensions for cathode ray tubes and their component parts. .- . EIA 493 A2 = 3234b00 0073494. T . RS-493 Page 1 RECOMMENDED PRACTICE FOR CONVERSION OF U.S. TO METRIC DIMENSIONS FOR COLOR AND MONOCHROME CATHODE RAY TUBES AND THEIR COM
10、PONENT PARTS (From EIA Standards Proposal No. 1543, formulated under the cognizance of EIA JT- 6 Committee on Television Picture Tubes.) 1.0 SCOPE 1.1 This procedure is recommended for the conversion of U.S. to metric dimensions in .the preparation of drawings, specif ications, and published data fo
11、r color and monochrome television picture tubes and their component parts. 1.2 Consideration has been given to both the ASTM (American Sotiet, for Testing and Materials) Metric Practice Guide and the IEC (International Electrotechnical Commission) Publication 191-1. This practice utilizes the proced
12、ures of both Standards which are most applicable to the specific requirements of color and monochrome television picture tubes. 2.0 UNITS 2.1 All metric dimensions shall be defined in millimeters, except the screen area shall be in square centimeters. 2.2 A decimal system shall be used with both inc
13、h and millimeter di- mensions. 2.3 To facilitate the reading of numbers having four or more digits, the digits should be placed in groups of three separated by a space instead of commas, counting both to the left and to the right of the decimal point. In the case of four digits, the space is optiona
14、l. 3.0 CONVERSION 3.1 Conversion shall be based on the conversion factor 1 inch = 25.4 mm exactly . 3.2 Round the millimeter values off to one decimal place less than the value shown in inches. Bogie (or nominal) values ending in the digits 5 to 9 shall be rounded upward, while values O to 4 shall b
15、e rounded downward. Tolerance (i.e. maximum and minimur, or both) values shall be rounded inwardly. EIA 493 82 m 3234b00 007L495-L m i , - RS-493 Page 2 . .-. 3.3 When. equations are specified, the calculations shall be made using inches and the result converted to ,millimeters, To convert the scree
16、n area from square inches to square centimeters, the value in square inches (to the closest square inch as specified in the latest issue of EIA Recammended Standard RS-324 “Registered Screen Dimensions for Color Picture Tubes“ (April, 1982) and EIA Recom- mended Standard RS-266 “Registered Screen Di
17、mensions for Mono- chrome Picture Tubes“ (March 1972; Reaffirmed Cpetember, 1979) shall be multiplied by 6.45. The result shall be rounded off to the nearest square centimeter. 3.4 4.0 FORMAT FOR DUAL DIMENSIONING 4.1 The dimensions for a dual C).S./Metric system shall be displayed by one of the fol
18、lowing methods depending on the type of drawing or textual mater i ai. 4.1.1 Tabulated with the metric (mm) dimension shown above the US. (inch) dimensions, or preceedinq the U.S. (inch) dimension in parenthesis, for example, Symbol Min. Bogie Max. L 529.21 20.835 531.57 20.928 533.93 21.021 or L 52
19、9.21(20.835) 531.57(20.928) 533.93(21.021) - 4.1.2 Dual dimensioning on the drawing shall be shown as illus- trated below: I Bogie Dimension ! 531.57 20.928 Toleranced Dimension 531.57 + 2.36 - 20.928 .O93 or - 531.57 (20.928) 531.57 - + 2.36 (20.928 - + ,093) NOTE: A key at the foot of the drawing
20、or table may be used to show the or mm (inches). inches mm method that has been followed, for example, - EIA 493 82 I 3234600 0071496 3 .- -7 RS-493 Page 3 4.1.3 In textual material, the U.S. dimension shall appear in parenthesis after the metric dimension, e.g., 51 mm (2 inches), or 50.8 mm (2.00 i
21、nches), 4.2 It is recommended that the following statement be included on drawings or textual material having dual dimensions: THE MILLIMETER DIMENSIONS ARE DERIVED FROM THE ORI- GINAL INCH DIMENSIONS (1 inch = 25.4 millimeters exactly). RELATED EIA RECOMMENDED STANDARDS RS-NO. Title Price RS-266-A
22、Registered Screen Dimensions for Monochrome $4.00 Picture Tubes (March 1972; Reaffirmed Spetember, 1979) RS-324-A Registered Screen Dimensions for Color Picture $4.00 Tubes (April, 1982) The above shown EIA Recommended Standards are available from: ELECTRONIC INDUSTRIES ASSOCIATION Engineering Department 2001 Eye Street, N.W. Washington, D.C. 20006
