ECA EIA-501-A-1990 Recommended Practice for the Measurement of X-Radiation from Raster-Scanned Direct-View Data Display Cathode-Ray Tubes.pdf

1、ANSI/EIA-501-A-1990 Approved: March 9,1990 Reaffirmed: February 28,2001 EIA STANDARD Recommended Practice for the Measurement of X-Radiation from Raster-Scanned Direct-View Data Display Cathode-Ray Tubes EIA-501-A (Revision of EM-501) MAY 1990 Electronic Components, Assemblies the TV X-I., or the Mo

2、del 49l,or equivalent. Thin window ion chamber survey meters may also be used. See ELA Consumer Products Engineering Bulletin No. 3 “Measurement Instnunentation for X-Radiation fiom Television Receivers“.) 3.1.2 X-Radiation Measuring Instrument The principal x-radiation measuring instrument shall co

3、mply with the requirements of Title 21, Code of Federal Regulations (CFR), Chapter I, Subchapter J, Section 1020.10, subparagraph (c)-(2), and with EIA Consumer Products Engineering Bulletin No3. The instrument shali provide x-radiation measurements (mRJh) or pA/Kg in the range of the applicable lim

4、it. The radiation volume shall have across-section parallel to the external surface of the hypothetical cabinet with an area of 10 cni! and no dimension larger than 5 cm. Measurement deviations due to instrument imprecision, energy dependence and other sources of error shall be commensurate with the

5、 current instrument art. An example of an instrument which hilfills these requirements is the 440 RF/C, or equivalent. Measurements with instruments having other areas must be corrected for spatial non-uniformity of the radiation field to obtain the exposure rate averaged over a 1 O cni! area. NOTE:

6、 A larger area detector may be used, prowed that the field is determined to be uniform over its aperture. Examples: 440 RF, 203A, and TV-150. 32 Test Equipment Stable electronic conditions must be provided for the operation of the tube under tbt and to measure anode voltage and current. 32.1 Anode V

7、oltage Metering System The recommended anode voltage divider and voltmeter with an overall accuracy of 2 0.1% and the digital readout using at least four significant tgures, having a sensitivity of at least 0.01 kV. me effect of the overall accelerating potential on the x-radiation characteristics i

8、s such that the x-radiation exposure rate could double for each 1 kV change of accelerator potential, thereby making accurate voltage measurements desirable.) If the recommended accuracy of the measurement system cannot be achieved, the inaccuracy shall be accounted for by reducing the recorded volt

9、age reading by the maximum possible measurement deviation. 32.2 Anode Current Metering System The recommended anode current metering system incorporates an overall accuracy of $I 1%. (The effect of the anode current on the x-radiation characteristics is that the x-radiation exposure rate is directly

10、 proportional to the anode current.) If the recommended accuracy of the anode current measurement system cannot be achieved, the inaccuracy shall be accounted for by reducing the recorded current reading by the maximum possible measurement deviation. EM-501-A Page 3 3.23 Power Supply for the Overall

11、 Accelerating Potential The recommended power supply for the overall acclerating potential incorporates a stabfiy of 0.05%. (The effect of the overall accelerating potential on the x-radiation characteristic iS according to paragraph 3.2.1, thereby making a stable power supply desirable.) If the rec

12、ommended shbility of the power supply cannot be achieved, the variation shall be accounted for by recording the lowest voltage reading during a specific x-radiation measurement. 32.4 Anode Connector Assembly See paragraphs 6.2 and 63. 4. CALIBRATION 4.1 The measuring instrument shall be calibrated b

13、y exposure to a uniform x-ray field having an exposure rate and energy representative of those to be measured. 4.2 The calibration shall be traceable to the National Institute of Standards and Technology (NIST). 5. TEST CONDITIONS 5.1 Tube Position The tube under test shall be positioned relative to

14、 the test equipment so that measurements may be made as specified in paragraph 6.0. 52 Extemg Components Ehternal components normaiiy mounted on the tube may be in place while obtainiag x-radiation characteristics. (Extemai components may indude deflection yokes, alignment coils, mounting hardware,

15、implosion protection mechanisms, etc.) 53 warm-up A warm-up period shali be provided for both the tube and test equipment in order to obtain stable operating conditions before proceeding with the measurement. Anode current shall not vary or drift more than $L 1% while measurements are bei made. 5.4

16、Display 5.4.1 Focus The tube under test shd be operated at optimum focus. 5.4.2 Blanking The tube shall be operated with dc voltage which result in an unb1anke-d raster. 5.4.3 Multiple Guns Multiple gun tubes may be operated using only one gun. . EIA-501-A Page 4 5.4.4 Raster Geometry The horizontal

17、 and vertid scan controls shall be adjusted so that the raster width and height are 90% of the screen width and height. The linearity of the scan shaii be checked and adjusted with a crosshatch pattern such that the &tance between crosshatch lines measured along the major and minor axes shaU be witb

18、iu 10% of the corresponding measurements at the center of the screen. The radius of mature of ali four raster sides shd not be less than 200 un. 6. PROCEDURE The x-radiation exposure rate shaU be measured as described below at the location of maximum intensity. The background radiation shall be veri

19、fied at the test position and corrections applied to the observed data as required. 6.1 Radiation from the Tube Face The radiation fiom the tube face shall be measured with the effective center of the detector 5 cm fiom the surface of the tube. NOTE: When the plastic spacers on the 440 RF/C Survey M

20、eter, or equivalent, are in contact with the tube face or the surface of the hypothetical cabmet, the distance from the surface to the effective center of the detector is 5 cm. The measured area of the tube face must be extended past the extremities of the actual faceplate to completely enclose the

21、effective volume of the hypothetid cabinet described in paragraph 6.4. This extension of the tube face is achieved by hypothetidy extending the major spherical curvature of the front face of the tube to the top, bottom and side surfaces of the hypothetical cabmet. The measuring instrument may be pla

22、ced anywhere over the tube face or over the hypothetid extension of it, provided that the center of the detectors front face does not overlap the top, bottom or sides of the hypothetical cabmet. 6.2 Radiation Emitted from the Funnel Portion Radiation emitted Erom the funnel portion of the entire tub

23、e (&clusive of the anode contad and tube face) shd be measured with the effective center of the detector 5 an from the surface of the hypohetica, non-absorbing cabinet that is desuii in paragraph 6.4 and shown ia Fie 2 The measuring instrument shai be positioned for maximum exposure rate with the fr

24、ont face of the detector pardel to the surface of the cabinet. The measuring instrument may be placed anywhere over the surface of the hypothetical cabinet desuibed in paragraph 6.4, provided that the center of the detectors front face does not overiap the outer edges of the surface of the hypotheti

25、cal cabmet that is bei measured. The anode contact shall be covered with a 2.5 cm diameter attenuating shield having a minimum absorption equivaient to 0.25 mm of lead and &ali be concentric with the anode contact, as shown in Figure 3. 6.21 Neck Radiation High voltage breakdown may occur at the ele

26、ctron gun under the stress of extremely high anode voltage. The resultant arcing or leakage, or both, may cause spurious x-radiation, which is independent of beam current, to emanate through the glass neck of the picture tube. When making measurements at anode voltages above the maximum rating of th

27、e tube, and it is desired to determine the exposure rate resulting from the beam current only the x-radiation from the neck of the tube should be shielded from the survey meter. EIA-501-A Page 5 63 Radiation Emitted Through the Anode Contact Radiation emitted through the anode contact shaU be measur

28、ed with the effective center of the detector 5 (mi from the surface of the hypothetical cabinet. (a) Electrical connection to the anode contact shaii be made with a non-attenuating wire connector shown in Figure i, and ) all of the glass surface of the anode contact side of the funnel portion (inclu

29、ding the frit seal area) shd be covered with an apertured shield of 6 mm maximum thickness, spaced a marhum of 3 mm from the funnel surface at the anode contact. A 25 cm diameter hole in the shield is centered around the anode contact. The minimum x-ray absorption of the shield shaU be equivalent to

30、 at least 0.25 mm of lead. 6.4 Hypothetica Cabinet The hypothetical cabinet is shown in Figure 2, the side of the hypothetical cabinet shall be 25 cm from the outside surface of the tube (excluding the extra thickness of any applied safety system, such as the tension band) at the ends of the major a

31、nd minor axes of the face. The back shall be formed in part by a vertical circular surface of 8.5 cm diameter concentric with the axis through the neck of the tube. This circular surface is to be located 2.5 cm behind the published maximum protrusion of the base of the tube, which is to be measured

32、relative to the center of the front face of the tube. The rear circular surface of the hypothetical cabiiet is then at a fixe distance behind the front face of the tube (for any given tube type), the actual distance beiig the maximum published overall length of the tube plus 2.5 cm. From the outer c

33、ircumference of this circular surface, a concentric conical surface is to extend forward at 49 to the tube axis uni3 the diameter of the conical section is inCreased to 285 cm. A vertical plane is then constructed radiating out from this maximum iameter of the cone, to form the remainder of the back

34、 of the cabinet as shown in Figure 2A Exceptions: The conical section will be completely removed for aU tube sizes with a minimum registered screen diagonal of less than 215 cm, and the back of the cabinet will be a flat vertical surface located 25 cm behind the published maximum protrusion of the b

35、ase of the tube as shown in Figure 2C. For all other tube sizes, where the resultant cabinet height is less than 285 cm, the maximum diameter of the conical section coincides with the maximum height of the cabinet. The vertica piane forming the remainder of the back of the cabinet is then constructe

36、d radiating from the maximum diameter of this shortened conical section as shown in Figure 2B. For convenience in locating the x-radiation search and measuring instruments with respect to the hypothetical surface, a box, or parts of a box, of the Size speafed may be constructed. However, while measu

37、rements are made in the vicinity of the maximum diameter of the conical section of the back of the cabinet, either the flat surface radiating from the maximum diameter of the cone, or the conical sedion, wiil have to be removed to allow the x-radiation measuring instrument to be placed on any part o

38、f that surface without hindrance from the other parts of the box The constructed box, or parts of the box, should be of a low absorbing material to prevent loss of measurement sensitivity. Unless the box is removed while measurements are being made, a correction factor must be determined over the vo

39、ltage range used for each meter location on the box being used and the x-radiation data adjusted accordingly. 6.5 Reading Technique 65.1 Model 440 RF/C - it is recommended that the 0-1 scalenot be used. The measurement period should not be less than 30 seconds. The lowest reading during the measurem

40、ent period should be recorded, ignoring sporadic downscale pulses. Background should be determined using the same technique. EM-501-A Page 6 65.2 During the test exposure period, the anode voltage and current shall be constantly monitored and the lowest observed values of each recorded. 7. REPORT 7.

41、1 Origin - Date - Observers Name - Laboratory - Procedure Used 7.2 Tube Identification 73 Extend shielding and components, including deflection yokes if used shall be speciEed together with their critical dimensions and their location on the tube. 7.4 The foilowing equipment information shall be on

42、record - Manufacturer - Serial Number - Accuracy Specification - Correction Factors, if applicable - calibration Date - Calibration Source and Accuracy - Any other pertinent information to qualify the results. This information is required for at least: - The anode voltage metering source. . - The an

43、ode current metering soure. - The principal x-radiation measuring instrument. 7.5 The foiowing data shaii be recorded: - Measurement Location - Gun or Guns Used - Anode Current - Overall Accelerating Potential - X-Radiation Reading - Background Reading. EM-501-A Page 7 EIA-501-A Page 8 -. .I . . Wir

44、e Connector (0.5 mm dia. max.1 FIGURE 1 Lead Glass DIAGRAM SHOWING CONSTRUCTION AND CONNECTION OF NON-AITENUATING WIRE CON“OR EIA-501-A Page 9 t I I U LARGE CRTs ( 235 cm BULB HEIGHT) NOTE: L = maximum published overd length (Figures 24,2B and 2C) SMALL CRTs (235 cm BULB HEIGHT 521.5 cm SCREEN DIAGO

45、NAL) t SI V1.i FIGURE 2C LI. I 1_ VERY SMALL CRTs ( 215 un SCREEN DIAGONAL) EIA-501-A Page 10 1 r“- 2-5 cm *la- Shieid - Hin. Absorption Equv. to 0.25 mm Lead 3 mrn max, e Lead (See Fg. 1) Funnel Clams Anode Contact . Centering Hans FIGURE 3 DETAIL OF ANODE CONNECTOR AND SHlELD EIA-501-A Page A-1 AP

46、PENDIX A DETERMINATION OF ATENUATION FACTTOR OF ANODE CONNECTORS A. Procedure A.l This procedure is the same as that in paragraph 63 except that the anode connector to be measured is used instead of the non-attenuating wire connector. The location of the maximum intensity of radiation should be dete

47、rmined by probiug, since it may differ from that found in paragraph 63 depending upon the connector design. With certain anode connector designs, the location and magnitude of maximum intensity may depend upon the connector orientation, therefore it may be necessary to probe for the maximum value wi

48、th the connector reinserted in different rotationai positions. A2 Attenuation Factor The attenuation factor at a particdar anode voltage is the quotient of the value determined by the procedure of paragraph 63 divided by the value determined by the above procedure when measured on the same tube. EIA

49、 Document Improvement Proposal Submitters Name: If in the review or use of this document, a potential change is made evident for safety, health or technical reasons, please fill in the appropriate information below and mail or FAX to: Telephone No.: FAX No.: e-mai 1 : Electronic Industries Alliance Technology Strategy & Standards Department - Publications Office 2500 Wilson Blvd. Arlington, VA 2220 1 FAX: (703) 907-7501 Document No. Document Title: Urgency of Change: Immediate: 0 At next revision: II Problem Area: a. Clause Number and/or Drawing: b. Recomme