1、BRITISH STANDARD AEROSPACE SERIES BS G242:1989 Specification for Data bus interconnecting systemsBSG242:1989 This BritishStandard, having been prepared under the directionof the Aerospace Standards Policy Committee, waspublished under the authorityof the Board of BSI andcomes into effect on 31Octobe
2、r1989 BSI01-2000 The following BSI references relate to the work on this standard: Committee referenceACE/6 Draft for comment86/72596DC ISBN 0 580 17108 6 Committees responsible for this British Standard The preparation of this BritishStandard was entrusted by the Aerospace Standards Policy Committe
3、e (ACE/-) to Technical CommitteeACE/6, upon which the following bodies were represented: British Airways BEAMA Ltd. British Cable Makers Confederation British Rubber Manufacturers Association Civil Aviation Authority Electronic Components Industry Federation Ministry of Defence National Supervising
4、Inspectorate Society of British Aerospace Companies Limited Amendments issued since publication Amd. No. Date of issue CommentsBSG242:1989 BSI 01-2000 i Contents Page Committees responsible Inside front cover Foreword ii 1 Scope 1 2 Definitions 1 3 Cable 1 4 Coupling 1 5 Couplers 3 6 Connectors 4 7
5、Terminators 4 8 Splices 4 Appendix A Surface transfer impedance measurement 5 Appendix B Data bus cable, dimensions and performance 7 Appendix C Transformer waveform integrity: droop test 11 Appendix D Concentric trinax removable contacts: intermateability dimensions 11 Figure 1 Data bus interface u
6、sing direct coupling for type A or type B systems 2 Figure 2 Data bus interface using transformer couplingfor type B systems 3 Figure 3 Surface transfer impedance test fixture for testingcablescreensandcables containing splices 6 Figure 4 Ancillary test fixture for measuring surface transferimpedanc
7、eofmated connectors 6 Figure 5 Ancillary test fixture for measuring surface transferimpedanceofcoupler housing 7 Figure 6 Typical construction details for data bus cable optimizedsinglescreen, multiplex, for type A systems 8 Figure 7 Typical construction details for data bus cable optimizeddoublescr
8、een, multiplex, for type B systems 9 Figure 8 Typical construction details for data bus cable superscreened,multiplex, for type B systems 10 Figure 9 Coupling transformer 11 Figure 10 Intermateability dimensions for size8 male contacts 11 Figure 11 Intermateability dimensions for size8 female contac
9、ts 12 Figure 12 Intermateability dimensions for size10 male contacts 12 Figure 13 Intermateability dimensions for size10 female contacts 13 Publications referred to Inside back coverBSG242:1989 ii BSI 01-2000 Foreword This BritishStandard, having been prepared under the direction of the Aerospace St
10、andards Policy Committee, gives guidance on the interconnection of data bus systems of all types used on aircraft, either civil or military. The data bus systems have been divided into type A and type B. Type A is intended to comply with the general requirements of ARINC429, which is usually called
11、up for civil aircraft. Type B will comply with the appropriate requirements of Def.Stan.00-18 and/or MIL-STD-1553B, which are generally the requirements for military systems. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are res
12、ponsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pagesi andii, pages1 to14, an inside back cover and a back cover. This standard has bee
13、n updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover.BSG242:1989 BSI 01-2000 1 1 Scope This BritishStandard establishes requirements for data bus interconnecting systems for aerospace applications. It defines
14、 the characteristics of the data bus line and components up to the interface with electronic components of the system. Digital data transmission systems fall basically into two categories working at data rates either above or below100kilobits/second. The electrical requirements of the components of
15、the transmission systems in these categories are different and the categories are classified in this standard as follows: type A systems, operating at rates of100kilobits/second or less; type B systems, operating at rates greater than100kilobits/second. NOTEThe titles of the publications referred to
16、 in this standard are listed on the inside back cover. 2 Definitions For the purposes of this BritishStandard the definitions given in BS9520 apply. 3 Cable 3.1 The cable used for the mains bus and all stubs shall be a two-conductor screened and jacketed twisted pair having a mutual capacitance not
17、exceeding98.4pF/m at a frequency of1kHz. The cable specification used shall include requirements for insulation and screening efficiency. 3.2 The cable shall be formed with not less than13twists per metre, where a twist is defined as a360 rotation of the wire pair. 3.3 The nominal characteristic imp
18、edance (Z 0 ) of cables for type A and type B systems shall be777. When measured at a frequency of1MHz, the impedance shall be77 77 for type A systems and77 37 for type B systems. 3.4 The cable attenuation shall not exceed4.92dB per100m at a frequency of1.0MHz. 3.5 The effectiveness of the cable scr
19、eening shall be determined by measuring the surface transfer impedance (Z t ) at a frequency of30MHz. Z tshall be not greater than100m7/m, at a frequency of30MHz unless a higher screening efficiency is called for in the detail specification. NOTE 1A typical method for the determination of surface tr
20、ansfer impedance is given in Appendix A and may be used pending publication of a definitive method which is under consideration. NOTE 2See Appendix B for typical cable constructions. 3.6 Cable classed as suitable for air frame use shall satisfy the electrical performance characteristics of this stan
21、dard and shall be suitable for use in the temperature ranges65 C to135 C,65 C to150 C,65 C to200 C, or65 C to260 C. The physical dimensions of these cables and their performance shall be as given in Appendix B and shall be in accordance with the appropriate test requirements of BS G230. 3.7 The two
22、ends of the data bus line shall be terminated with a resistance equal to the nominal characteristic impedance (Z 0 ) 2% (see clause7). The termination shall be screened and the effectiveness of the screening shall be determined by measuring Z t , which shall be not greater than10m7 at30MHz for use o
23、n type A or type B systems. 4 Coupling 4.1 Cable stub connections for type A systems 4.1.1 Cable stub connections for type A systems shall be direct, as shown in Figure 1, and shall not exceed0.3m in length. 4.1.2 The electrical connections of the conductors of the stub to those of the bus shall be
24、soldered in accordance with an acceptable quality standard, or crimped, in which case the connections shall comply with the applicable performance requirements of BS4G178-1. 4.1.3 The screening of the connection shall be continuous and provide360 coverage. The effectiveness of screening of the stub
25、connection shall be determined by measurement of the surface transfer impedance (Z t ) of an assembly at a frequency of30MHz. Z tshall be not greater than100m7/m for type A systems and10m7/m for type B systems. 4.2 Cable stub connections for type B systems Cable stub connections for type B systems s
26、hall be as shown in Figure 2. Transformer coupled stubs (see Figure 2) shall be as short as practicable and shall not exceed6.1m in length. NOTEThe distance between stubs and their lengths may have to be adjusted so as to avoid digital errors arising from spurious pulse reflections.BSG242:1989 2 BSI
27、 01-2000 Figure 1 Data bus interface using direct coupling for type A or type B systemsBSG242:1989 BSI 01-2000 3 5 Couplers 5.1 No resistors or transformers shall be used in type A systems. 5.2 For type B systems, couplers shall consist of a coupling transformer and two fault isolation resistors con
28、tained within a screened, environmentally sealed and corrosion resistant enclosure. NOTEThe enclosure may contain more than one coupling transformer and associated resistors. When an enclosure contains more than one coupling transformer particular attention should be paid to the stub lengths (see4.2
29、). Couplers may be connected to the data bus and stubs with connectors or may be provided with cables installed during manufacture. These may be connected to the system with permanent splices, as specified in clause8. 5.3 The screening effectiveness of the enclosure shall be determined by measuring
30、the surface transfer impedance (Z t ) at30MHz of a length of data bus cable connected to the enclosure. Z tat30MHz for the assembly shall be not greater than10m7 plus10m7/m for the length of cable used. 5.4 The transformer in the coupler shall comply with the following requirements: a) turns ratio:
31、1.41 to1,3%; b) input impedance:3k7 minimum(75kHz to1.0MHz) measured with a1V r.m.s. sine wave; c) droop: 20% maximum(250kHz), measured in accordance with Appendix C; d) overshoot and ringing: 1.0V peak(250kHz square wave,27V peak to peak with100ns maximum rise and fall time); e) common mode rejecti
32、on: greater than45.0dB at1.0MHz measured with a10Vr.m.s. sine wave input; f) fault protection: resistors in series with each connection equal to0.75Z o 2%7; Figure 2 Data bus interface using transformer coupling for type B systemsBSG242:1989 4 BSI 01-2000 g) transformer leakage inductance: not great
33、er than54H measured with1V r.m.s. sine wave at1MHz. NOTECare should be taken to ensure that couplers incorporating transformers are not installed in areas subject to upper temperatures in excess of their capabilities as declared. 6 Connectors 6.1 Connectors 6.1.1 Connectors shall comply with the app
34、licable requirements of BS G202. 6.1.2 Inserts of single cavity and multicavity connectors employing concentric twinax contacts shall be of one of two types: a) those retaining the isolation of the screens of the concentric twinax contacts; b) those earthing to connector shell the screen of the conc
35、entric twinax contacts. 6.1.3 Connectors shall maintain360 screening and continuity of screening over their entire length. 6.1.4 The effectiveness of screening shall be determined by measuring the surface transfer impedance (Z t ) at30MHz. Z tshall not exceed100m7 for type A systems and10m7 for type
36、 B systems. 6.1.5 The connector shall be capable of operating within the preferred temperature range65 C to135 C,65 C to150 C,65 C to200 C, or65 C to260 C. 6.2 Contacts Contacts shall comply with BS9521. NOTEPreferred contact interface dimensions should be as given in Appendix D for sizes8 and10. 7
37、Terminators A terminator shall be a self-contained device for terminating each end of the data bus line as required by3.7. It shall take the form of a screened housing containing the necessary resistor and shall be joined to the data bus line by means of a connector or permanent splice (see clause8)
38、. 8 Splices 8.1 Splices, incline or multiple, shall comply with BS G180. 8.2 Splices in the cable shall maintain360 screening and continuity of the screen over the entire length of the splice. 8.3 The effectiveness of screening shall be determined by measuring the surface transfer impedance (Z t ) a
39、t30MHz of a length of data bus cable containing a splice. Z tat30MHz shall not increase by more than5.0% when compared with the parent cable. 8.4 The impedance mismatch at the splice, as measured on a time domain reflectometer, shall not exceed the tolerance allowable for the characteristic impedanc
40、e of the cable (Z o ) given in3.3. 8.5 The completed splice shall be fully insulated and environmentally sealed. After being subjected to the immersion (low air density) test given in clause10 of BS5772-7:1981 at4kPa the measured insulation resistance shall be not less than1000M7. 8.6 The splice sha
41、ll be capable of operating within the same temperature range as the cable.BSG242:1989 BSI 01-2000 5 Appendix A Surface transfer impedance measurement A.1 General The method is generally in accordance with IEC Publication96, except that some changes have been made to the apparatus to allow irregularl
42、y shaped components to be tested. A.2 Apparatus A.2.1 General. IEC Publication96 describes a coaxial arrangement for testing cable screens. This is satisfactory for rigid cables but not always for flexible cable where sagging of the cable can cause difficulty in achieving reproducible measurements.
43、It is not possible to test irregularly shaped components exactly as given in IEC Publication96. Modifications of the apparatus to accommodate all anticipated types of components are described inA.2.2 toA.2.4. A.2.2 Cables and splices. The outer coaxial tube used as a circuit drive line is dispensed
44、with and replaced by a length of tinned copper braid drawn down onto the cable jacket. The braid accommodates varying cross sections, e.g.splices in the cable, and also minimizes problems caused by flexible cables sagging inside a coaxial tube which can cause difficulties in achieving reproducible r
45、esults. When measurements are being taken on a cable sample, it should be kept as straight as possible as bending may give inconsistent results. The test fixture for testing cable screens and cables containing splices is shown in Figure 3. A.2.3 Connectors. Each half of a mating pair of connectors,
46、complete with contacts, is mounted by use of suitable adaptors on a copper extension tube. Each connector has a length of cable connected to one nominated contact, the chosen contact in one half mating with the chosen contact in the other half of the mating pair. The connectors are mated and the ass
47、embly installed in an outer high-conductivity copper tube as shown in Figure 4. This subassembly is connected to the current source and voltage measuring device, with suitable amplifiers, in place of the triaxial cable assembly in Figure 3 and measurements are carried out as for cables. A.2.4 Couple
48、rs. The active components are removed from the coupler housing. A cable is passed through the housing to act as an aerial during the test. If the housing has additional openings, these are closed off with high-conductivity copper tubes and plugs to eliminate radiation from them. This subassembly is
49、enclosed within a suitable high-conductivity copper tube or box which becomes the circuit drive line, as shown in Figure 5. It is connected to the current source and voltage measuring device, with suitable amplifiers, in place of the triaxial cable assembly in Figure 3 and measurements are carried out as for cables. BSG242:1989 6 BSI 01-2000 Figure 3 Surface transfer impedance test fixture for testing cable screens and cables containing splices Figure 4 Ancillary test fixture for measuring surface transf
