1、BRITISH STANDARD BS EN 61237-1:1995 IEC1237-1: 1994 Broadcast video tape recorders Methods of measurement Part1: Mechanical measurements The European Standard EN61237-1:1994 has the status of a BritishStandard UDC 621.397.452:621.317.08BSEN61237-1:1995 This BritishStandard, having been prepared unde
2、r the directionof the ElectrotechnicalSector Board,was published undertheauthority of theStandards Board and comesintoeffect on 15 January 1995 BSI 01-2000 The following BSI references relate to the work on this standard: Committee reference EEL/22 Draft for comment91/03062DC ISBN 0 580 23544 0 Coop
3、erating organizations The European Committee for Electrotechnical Standardization (CENELEC), under whose supervision this European Standard was prepared, comprises the national committees of the following countries: Austria Italy Belgium Luxembourg Denmark Netherlands Finland Norway France Portugal
4、Germany Spain Greece Sweden Iceland Switzerland Ireland UnitedKingdom Amendments issued since publication Amd. No. Date CommentsBSEN61237-1:1995 BSI 01-2000 i Contents Page Cooperating organizations Inside front cover National foreword ii Foreword 2 Text of EN61237-1 3 National annex NA (informative
5、) Committees responsible Inside back cover National annex NB (informative) Cross-references Inside back coverBSEN61237-1:1995 ii BSI 01-2000 National foreword This BritishStandard has been prepared under the direction of the Electrotechnical Sector Board and is the English language version of EN6237
6、9-1:1994 Broadcast video tape recorders Methods of measurement. Part1: Mechanical measurements, published by the European Committee for Electrotechnical Standardization (CENELEC). It is identical with IEC1237-1:1994, published by the International Electrotechnical Commission (IEC). BS EN61237 consis
7、ts of the following Parts: Part 1: Mechanical measurements; Part 2: Electrical measurements for analogue composite video signals; Part 3: Electrical measurements for analogue component video signals; Part 4: Measurement of audio performance-analogue. A British Standard does not purport to include al
8、l the necessary provisions of a contract. Users of British Standards are responsible 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 andi
9、i, theEN title page, pages2 to12, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover.EUROPEAN STANDARD NORME EUROPENNE EUROPISCHE NORM EN61237-1 J
10、uly 1994 UDC 621.397.452:621.317.08 Descriptors: Electroacoustics, video recording, recording apparatus, video tape recorders, radiocommunications, mechanical measurements, compatibility English version Broadcast video tape recorders Methods of measurement Part1: Mechanical measurements (IEC1237-1:1
11、994) Magntoscopes de radiodiffusion Mthodes de mesure Partie1: Mesures mcaniques (CEI1237-1:1994) Meverfahren fr Videobandgerte fr den Rundfunk Teil1: Mechanische Messungen (IEC1237-1:1994) This European Standard was approved by CENELEC on 1994-03-08. CENELEC members are bound to comply with the CEN
12、/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the Central Secretariat or to
13、any CENELEC member. This European Standard exists in three official versions (English, French, German). A version in any other language made by translation under the responsibility of a CENELEC member into its own language and notified to the Central Secretariat has the same status as the official v
14、ersions. CENELEC members are the national electrotechnical committees of Austria, Belgium, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy,Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and UnitedKingdom. CENELEC European Committee for Electrotechnical Stand
15、ardization Comit Europen de Normalisation Electrotechnique Europisches Komitee fr Elektrotechnische Normung Central Secretariat: rue de Stassart 35, B-1050 Brussels 1994 Copyright reserved to CENELEC members Ref. No. EN61237-1:1994 EEN61237-1:1994 BSI 01-2000 2 Foreword The text of document60B(C0)15
16、8, as prepared by Sub-committee60B: Video recording, of IEC Technical Committee60: Recording, was submitted to the IEC-CENELEC parallel vote in April 1993. The reference document was approved by CENELEC as EN61237-1 on 8 March 1994. The following dates were fixed: Annexes designated “normative” are
17、part of the body of the standard. Annexes designated “informative” are given only for information. In this standard, Annex A and Annex ZA are normative and Annex B is informative. Contents Page Foreword 2 1 Scope 3 2 Normative references 3 3 General 3 4 Test conditions 3 5 Measuring equipment 3 5.1
18、Mechanical measurements 3 5.2 Optical measurements 3 6 Recorder measurements 4 6.1 Diameter of drum 4 6.2 Projection of video head pole tips 4 6.2.1 Mechanical measurement 4 6.2.2 Optical measurement 4 6.3 Gap width of video heads 4 6.4 Coplanarity error of video heads 4 7 Measurements on recorded t
19、ape 4 7.1 Tape speed and pitch of the video tracks 5 7.1.1 Tape speed v (first method) 5 7.1.2 Track pitch J (first method) 5 7.1.3 Tape speed and pitch of the video tracks (second method) 5 7.2 Position of the video reference point (VRP) 5 7.2.1 Measurement of the VRP position (first method) 6 Page
20、 7.2.2 Tracking and drum phase error (second method) 6 7.3 Location of records on sound and time code tracks 6 7.3.1 Track location to the reference tape edge 6 7.3.2 Longitudinal location of records 6 7.4 Video track geometry 6 7.4.1 Video track width I 6 7.4.2 Cross-tape measuring technique (first
21、 method) 6 7.4.3 Dynamic track measurement (second method) 7 Annex A (normative) Magnetic development of recordedtape 11 Annex B (informative) Bibliography 11 Annex ZA (normative) Other international publications quoted in this standard with thereferences of the relevant European publications 12 Fig
22、ure 1 Cross tape measuring technique 9 Figure 2 Example Track location error plot 10 latest date of publication of an identical national standard (dop) 1995-06-01 latest date of withdrawal of conflicting national standards (dow) 1995-06-01EN61237-1:1994 BSI 01-2000 3 1 Scope This part of IEC1237 des
23、cribes the mechanical measurement methods on video tape recorders relating to the compatibility parameters for recording and measuring methods of the recorded tape. The allowable tolerances for the rated values for acceptable performance are not given in this standard, but may be derived from the sp
24、ecifications for the related system i.e.appropriate publications, manufacturers specifications, etc. The necessary reference and calibration tapes are either mentioned in the specific IEC publication of the equipment under test or included in IEC1105. This standard deals with special mechanical meas
25、urement techniques for broadcast VTRs. It does not, however, cover the special mechanical measurements of the earlier transverse track video recorder standard (IEC347). For those measurements seeIEC1055. The methods are applicable to acceptance tests, performance comparison and, as far as possible,
26、for routine checks. 2 Normative references The following normative documents contain provisions which, through reference in this text, constitute provisions of this part of IEC1237. At the time of publication, the editions indicated were valid. All normative documents are subject to revision, and pa
27、rties to agreements based on this part of IEC1237 are encouraged to investigate the possibility of applying the most recent editions of the normative documents indicated below. Members of IEC and ISO maintain registers of currently valid International Standards. IEC347:1982, Transverse track video r
28、ecorders. IEC461:1986, Time and control code for video tape recorders. IEC1055-1:1991, Measurement techniques and operational adjustments of broadcast VTRs Part1:Operational adjustments on analogue composite broadcast VTRs (Report). IEC1055-2:1991, Measurement techniques and operational adjustments
29、of broadcast VTRs Part2:Special mechanical measurements and alignments (Report). IEC1105:1991, Reference tapes for video tape recorder systems. 3 General To ensure that the results obtained at a specific time and at a specific place are comparable to other measurements, it is advisable to specify th
30、e test signals, measuring devices and types of tapes used together with the results obtained. 4 Test conditions If not otherwise stated, all measurements shall be carried out at the following atmospheric conditions: 5 Measuring equipment 5.1 Mechanical measurements For some measurements, precision m
31、icrometers or dial indicators with14m resolution are sufficient. Instruments with electrical read-out should be preferred. For drum geometry measurements a three-coordinate measuring device with an accuracy below14m is recommended. 5.2 Optical measurements Measurements are made by a high power micro
32、scope equipped with an X-Y-table and a scaled Z-axis. temperature 20 C 1 C; relative humidity 50% 26%; air pressure 86kPa to106kPa; conditioning before testing 24h.EN61237-1:1994 4 BSI 01-2000 For measurements in the4m area the microscope objective shall have a magnification of50 and a numerical ape
33、rture of0,85. The eye-piece, equipped with cross-hairs shall have a magnificationU 10. A video camera/monitor system with electronic cross-hairs gives better reproducible results. The X-Y-table shall have a measuring range of at least100mm 50mm. The measuring accuracy in X-, Y- and Z-axis shall bek1
34、4m. For data acquisition and processing a computer is recommended. 6 Recorder measurements 6.1 Diameter of drum The drum is measured by means of a precision micrometer or a multicoordinate measuring system. Measurements are made at several points of the drum, and these points shall be specified by t
35、he appropriate standard or the manufacturer. 6.2 Projection of video head pole tips 6.2.1 Mechanical measurements Measurements are made by means of a precision dial indicator. Usually either the upper or the lower drum serves as reference, depending on the specifications of the standard or of the VT
36、R manufacturer. The measuring device is specified and often supplied by the VTR manufacturer. Instructions and precautions are given in the users manual of the measuring device. 6.2.2 Optical measurements The scanner is mounted on the microscope table with the rotating axis parallel to one table axi
37、s. Adjust the second table axis so that the optical axis crosses the rotating axis and lock. Focus to the drum surface at the reference area as specified and set the Z-axis measure to zero. Shift the table and rotate the drum till the video head gap under test is at the image center. Focus to the he
38、ad gap and read the tip projection in the Z-axis. 6.3 Gap width of video heads (The dimension of magnetic gap parallel to the plane of the tape and perpendicular to the direction of the relative tape to head movement) Scanner mounting is the same as in6.2.2. Focus on the head gap under test and meas
39、ure the head gap width. For azimuth heads measure the projected width of the gap. 6.4 Coplanarity error of video heads Scanner mounting is the same as in6.2.2, rotate from head to head. The center of the head gap width is the standard measuring point for all play heads and guard band recording heads
40、. In systems with overlap recording (gap width is more than the track pitch), the gap edge of the record or erase head which overlaps the prior recorded track is to be measured. In systems with separate video heads for record, play and erase the video heads are located in different planes. If the vi
41、deo heads of one type (e.g.record) are not in a constant angular distance it yields in an axial displacement. This displacement shall be considered so that all video heads of one type are measured in one plane (e.g.record plane). The coplanarity error is the peak-to-peak deviation in one plane. The
42、result is measured in micrometers, center measure or corner measure shall be stated. 7 Measurements on recorded tape A first method is to record a tape and make the magnetic footprint on tape visible by developing it by means of a suspension of ferro-magnetic powder. Methods for this developing are
43、described in Annex A. Measurement is then made by the microscope. This method is precise and gives absolute values.EN61237-1:1994 BSI 01-2000 5 A second method is to playback a calibration tape. This method is practice-orientated and gives a quick overview. Dynamic effects become visible. The result
44、s are less accurate because the errors of the calibration tape are always implemented and influenced by ageing. Good results are obtained by comparing recordings of the same calibration tape at the same time. 7.1 Tape speed and pitch of the video tracks On video tape recording are tape speed v, trac
45、k pitch J and control pulse distances in a fixed relationship, defined by the recording standard. With one measurement the others can be calculated. For measurement, the control track is to be used. 7.1.1 Tape speed v (first method) The tape speed results from the control track pulse distance divide
46、d by the basic time interval T. For high accuracy it is advisable to use a number of pulses n with a low repetition rate (edit pulse, colour frame pulse) for measurement so the measuring L distance will be in the range of about100mm. Tape speed v=L/(n T) mm/s 7.1.2 Track pitch J (first method) The t
47、rack pitch is the average distance of the track centers measured perpendicular to the recorded tracks. Track pitch J=L sin(F)/(n m)4m Longitudinal track pitch S=L/(n m)4m 7.1.3 Tape speed and pitch of the video tracks (second method) Measurement is made by comparing the tape speed v rin normal recor
48、d mode (not an insert mode) and the tape speed v cby playing back the calibration tape. Measure the capstan tachometer frequency f rin normal record mode and divide by the capstan tachometer frequency f cplaying back the calibration tape. Tape speed v=v c f r /f cmm/s Track pitch J=J c f r /f cmm 7.
49、2 Position of the video reference point (VRP) In most VTR standards one point of the video track is defined by a particular recording. Nomenclature T : basic time interval between control pulses; t : measured time intervals; F : basic track angle; L : distance for n control track pulses; v : tape speed; V ht : relative head to tape speed; n : number of control track pulses in distance L; m : number of tracks recorded during time interval T; l : track width; J : track pitch; S : longitudinal track pitch; P
