1、AECMA STANDARD NORME AECMA AECMA NORM Edition approved for publication 30 September 2004 prEN 3475-705 Edition P 2 September 2004 Comments should be sent within six months after the date of publication to AECMA-STAN ICs: 49.060 Descriptors: ENGLISH VERSION Aerospace series Cables, electrical, aircra
2、ft use Test methods Part 705: Contrast measurement Will supersede EN 3475-7052002 Srie arospatiale Luft- und Raumfahrt Mthodes dessais Prfverah ren Cbles lectriques usage aronautique Partie 705 : Mesure de contraste Elektrische Leitungen fr Luftfahrtverwendung Teil 705: Kontrastmessung This “Aerospa
3、ce Series“ Prestandard has been drawn up under the responsibilify of AECMA-STAN (The European Association of Aerospace Industries - Standardization). It is published for the needs of the European Aerospace Industry. It has been technically approved by the experts of the concerned Domain following me
4、mber comments. Subsequent to the publication of this Prestandard, the technical content shall not be changed to an extent that interchangeability is affected, physically or functionally, without re-identification of the standard. After examination and review by users and formal agreement of AECMA-ST
5、AN, it will be submitted as a draft European Standard (prEN) to CEN (European Committee for Standardization) for formal vote and transformation to full European Standard (EN). The CEN national members have then to implement the EN at national level by giving the EN the status of a national standard
6、and by withdrawing any national standards conflicting with the EN. Electrical Domain I I Copytight 2004 O by AECMA-STAb Copyright Association Europeene des Constructeurs de Materiel Aerospatial Provided by IHS under license with AECMANot for ResaleNo reproduction or networking permitted without lice
7、nse from IHS-,-,-Page 2 prEN 3475-705:2004 Foreword This standard was reviewed by the Domain Technical Coordinator of AECMA-STANS Electrical Domain. After inquiries and votes carried out in accordance with the rules of AECMA-STAN defined in AECMA- STANS General Process Manual, this standard has rece
8、ived approval for Publication. Contents Page O 1 2 3 4 4.1 4.2 4.2.1 4.2.2 4.2.3 4.2.4 4.2.5 4.2.6 4.2.7 4.2.8 4.2.9 4.3 4.3.1 4.3.2 4.3.3 4.3.4 4.4 4.5 Introduction Scope Normative referen ces Definitions Requirements Preparation of samples Test equipment Components of the measuring device Equipmen
9、t colour Photometer Illumination and viewing system Equipment design and measurement methodology Measurement spot size Measurement area Calibration Measurement tolerance Measurement process Precautionary measures Picture definition Sample area Number and location of measurements Determination of con
10、trast values Requirement 3 3 3 3 4 4 4 4 4 5 5 5 5 5 5 5 6 6 6 6 6 7 7 Copyright Association Europeene des Constructeurs de Materiel Aerospatial Provided by IHS under license with AECMANot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Page 3 prEN 3475-705:2004 O Intr
11、oduction It is a requirement within the aerospace industry that all wires and cables within an aircraft electrical system are identified with a circuit identification code at regular intervals down the length of the wire. Various marking methods are used for marking these identification codes on to
12、the surface of electrical wires or cables including ink based and laser based processes. The legibility of the markings is dependent upon the process used and the insulation medium. Minimum standards of contrast are required to facilitate reading back of the identity codes. 1 Scope This standard spe
13、cifies the process to be applied for measuring the contrast of wire and cable identification markings against the background of the unmarked wire insulation. It has been developed primarily to define a reproducible process of contrast value determination for use both to determine the intrinsic laser
14、 markability of wires at the time of manufacture or later, and to enable electrical wiring systems manufacturers to ensure that the whole process of wire marking is carried out to the required standard. 2 Normative references This European Standard incorporates by dated or undated reference, provisi
15、ons from other publications. These normative references are cited at the appropriate places in the text and the publications are listed hereafter. For dated references, subsequent amendments to or revisions of any of these publications apply to this European Standard only when incorporated in it by
16、amendment or revision. For undated references the latest edition of the publication referred to applies (including amendments). IS0 7724-1, Paints and varnishes - Colorimetry - Part 1: Principles EN 3475-706, Aerospace series - Cables, electrical, aircraft use - Test methods - Part 706: Laser markab
17、ility IEC 15-2, Colorimetry TR 4543, UV laser wire marking systems for aircraft wire and cable identification 3 Def i n i ti ons For the purpose of this standard the following terms and definitions apply. 3.1 contrast the ratio of the difference in luminance between the marked and unmarked areas of
18、the insulation divided by the luminance of the unmarked insulation 3.2 luminance the quantitative measurement of the visible light reflected from a surface, in this case the wire or cable insulation 1) In preparation at the date of publication of this standard Copyright Association Europeene des Con
19、structeurs de Materiel Aerospatial Provided by IHS under license with AECMANot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Page 4 prEN 3475-705:2004 3.3 laser laser is an acronym for Light Amplification by the Stimulated Emission of Radiation. Lasers are a source o
20、f intense monochromatic light in the ultraviolet, visible or infrared region of the spectrum. 3.4 ultraviolet (abbreviation UV) electromagnetic radiation in a wavelength range from approximately 200 nm to 400 nm 3.5 UV laser a laser that produces a beam of UV radiation 3.6 f I uence the energy densi
21、ty, measured in J cm- (Joules per square cm) of a single pulse of the laser beam, which, for the purposes of this document, is taken at the surface of the wire insulation or cable jacket 3.7 wavelength wavelength (A) is measured in nanometres, nm. 1 nm = IO- m. h = c/fwhere c is the velocity of ligh
22、t andfis the frequency 4 Requirements 4.1 Preparation of samples The wire or cable samples shall be identified in accordance with the applicable manufacturing instructions for the marking equipment. Where samples are to be UV laser marked this shall be done using the fluence specified in TR 4543 or
23、the relevant wire or aircraft manufacturers process specification if different. When determining the laser markability of wires, this shall be in accordance with EN 3475-706. Take a sample of the wire for marking. Before marking the wire ensure that the wire surface is clean and dry and free from du
24、st and dirt; if necessary wipe it clean using propan-2-01 (isopropyl alcohol). The surfaces of the samples shall be clean and without damage. The identification markings to be measured shall be even in colour and characters shall have well defined edges. Before starting measurements clean the surfac
25、es with a soft, lint-free cloth, if required, to avoid distortion of test results by a roughened surface or “deposits”. 4.2 Test equipment 4.2.1 The measuring device shall comprise, at a minimum, a photometer, an illumination system and a purpose designed sample holder suitable for wire and cable. T
26、he whole system shall be designed to ensure that test results are not falsified by external influences. The photometer shall be designed to be stable and free from vibrations and to exclude the influences of external light and reflections from scattered light. Components of the measuring device 4.2.
27、2 Equipment colour The device for holding samples and any accessories and the equipment in the vicinity of the measurement area shall be matt black in colour to absorb scattered light. Copyright Association Europeene des Constructeurs de Materiel Aerospatial Provided by IHS under license with AECMAN
28、ot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Page 5 prEN 3475-705:2004 4.2.3 Photometer The luminance shall be determined with a calibrated electrical photometer, which shall incorporate a photopic filter to simulate the response of the human eye. The manufacture
29、rs instructions concerning the photometer working range and operating instructions shall be observed. The measurement sensitivity of the photometer shall be in conformity with IEC publication 15-2. 4.2.4 Illumination and viewing system The illumination system shall consist of two light sources of eq
30、ual intensity (see Figure 1). The two sources may be two separate lamps or, preferably, two fibre light guides fed from a single lamp. The light from the sources shall overlap to illuminate a central spot on the sample at an angle of 45“ to the surface. The light cones shall illuminate the wire samp
31、le longitudinally along its length and in a manner to avoid the formation of shadows. The photometer must be installed to view the sample along the normal to the surface, .e. at go“, and above the principal focus at a distance that depends on the objectives focal distance. It shall be adjusted durin
32、g calibration and after every change of objective. If two separate lamps are used they shall be of identical power consumption and shall always be exchanged in pairs. The radiating light energy and colour temperature of the lamps shall be compatible with the working range of the photometer, accordin
33、g to the manufacturers instructions. The spectral distribution of the light shall be close to artificial light specifications according to light standard A, IS0 7724-1. Only gas filled lamps with tungsten filaments shall be used. The colour temperature shall be (3 O00 k 500) K. The voltage supply fo
34、r the lamps shall be insensitive to line fluctuations. A stabilised d.c. power unit shall be used. 4.2.5 To determine the contrast, measurements must be taken of the luminance from both marked and unmarked areas of the insulation. Depending upon the contrast measurement equipment design, the photome
35、ter may be used either to take a series of individual point measurements sequentially or it may determine the contrast instantaneously by the simultaneous measurement of the luminance of all the sample points of an area of the sample. If a point measurement system is used, sufficient points shall be
36、 sampled on both the marked and unmarked portion of the wire to ensure that a good average value of the reflectance of each is obtained. Equipment design and measurement methodology 4.2.6 Measurement spot size The maximum admissible diameter of the photometer measurement spot shall be not in excess
37、of 75 % of the character stroke width. This is particularly important if using a point measurement system where spot sizes are typically relatively large. 4.2.7 Measurement area The contrast shall be measured over a finite area to include a significant portion of the marked and the unmarked surface
38、of the wire. It is important that spot measurements should not be made immediately adjacent to the edge of a character, either on the mark or the unmarked insulation, to avoid scattered light from the adjacent area from interfering with the measurement. Area measurement systems should discriminate a
39、gainst such scattered light by suitable means. 4.2.8 Calibration The photometer shall be calibrated by use of a reference sample, e.g. ceramic tiles, of known reflectance, certified and traceable to National Standards. The frequency of calibration shall be in accordance with the equipment manufactur
40、ers guidelines. 4.2.9 Measurement tolerance The measuring tolerance of the photometer shall be not more than 2 %. Copyright Association Europeene des Constructeurs de Materiel Aerospatial Provided by IHS under license with AECMANot for ResaleNo reproduction or networking permitted without license fr
41、om IHS-,-,-Page 6 prEN 3475-705:2004 4.3 Measurement process 4.3.1 Precautionary measures There may be a danger from some illumination systems that they may cause the samples to heat up significantly. If this is the case then measurements should be taken without delay and the sample removed from the
42、 test area after the measurements have been taken. Contrast measurements shall not be taken in areas of the sample a) incorporating the wire manufacturers markings, b) for tape wrapped wires, in areas where the tapes overlap, or c) where there are visible inclusions, deformities or other surface irr
43、egularities, as these can all cause errors in the determination of the contrast value. NOTE If checking for repeatability it is of the utmost importance to ensure that the same character of the same mark and the same position within the character are measured each time. Significant variations in con
44、trast may occur otherwise. WARNING taken when interpreting the contrast results of some dark coloured wires. The contrast formula in 4.4 is limited in its application to white and light coloured wires. Care must be 4.3.2 Picture definition The image of the markings and the wire or cable surface shal
45、l be adjusted to ensure that it is sharp and in focus. However, care should be taken NOT to make such adjustments unnecessarily, as this may then require the equipment to be recalibrated. Refer to the manufacturers instructions. 4.3.3 Sample area When measuring the contrast of the marks ensure that
46、measurements are made on the marked and unmarked areas about the central axis of the wire, along its length, and just either side, within a band equal to k 20 % of the diameter of the wire or cable (on small gauge wires this may not be possible due to the limited size of the wire). This is to ensure
47、 that the most uniform part of the mark is measured so that errors are not introduced caused by changes in the laser fluence resulting from the curvature of the wire. See Figure 2. 4.3.4 To ensure a statistically meaningful result, a sufficient number of measurements must be made to take into accoun
48、t variations in the measurement process, including any that may result from the operator as well as from the wire and the markings. It is important to ensure that a good average value for the overall contrast measurement for the sample is obtained, regardless of the equipment and the means used. Con
49、trast measurements should be made at multiple points from within the selected wire marking, over a minimum length of 50 mm. Contrast values should be calculated for a minimum of 3 separate characters within the sample marking and these should be used to produce an average measurement. Characters should be sampled from either end and in the middle of the code or wire marking. See Figure 2. Note that there are generally two different approaches to contrast measure
