Information technology — Data interchange on 12,7 mm 128-track magnetic tape cartridges — DLT 4 format

Technologies de l'information — Échange de données sur cartouches de bande magnétique de 12,7 mm, 128 pistes — Format DLT 4

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ISO/IEC 15307:1997 - Information technology -- Data interchange on 12,7 mm 128-track magnetic tape cartridges -- DLT 4 format
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First edition
Information technology - Data interchange
on 12,7 mm 128-track magnetic tape
cartridges - DLT 4 format
Technologies de I’informa tion - khange de donnkes sur carfouches de
bande magnetique de 12,7 mm, 128 pistes - Format DLT 4
---------------------- Page: 1 ----------------------
ISO/IEC 15307: 1997 (E)
Section 1 - General
1 Scope
2 Conformance
2.1 Magnetit tape cartridges
2.2 Generating Systems
2.3 Receiving Systems
3 Normative references
4 Definitions
4.1 Average Signal Amplitude
4.2 azimuth
4.3 back surface
4.4 Beginning-Of-Tape marker (BOT)
4.5 byte
4.6 cartridge
4.7 Cyclic Redundancy Check (CRC) Character
4.8 Early Warning (EW)
4.9 Error-Detecting Code (EDC)
4.10 End-Of-Tape marker (EOT)
4.11 Entity
4.12 Error-Correcting Code (ECC)
4.13 flux transition Position
4.14 flux transition spacing
4.15 Logical Block
4.16 logical track
4.17 magnetic tape
4.18 Master Standard Reference Tape
4.19 Object
4.20 page
4.21 physical block
4.22 physical recording density
4.23 physical track
4.24 Record
4.25 Reference Edge
4.26 Reference Field
4.27 Secondary Standard Reference Tape
4.28 Standard Reference Amplitude (SRA)
4.29 Standard Reference Current
4.30 Test Recording Current
4.31 Typical Field
@lSO/lEC 1997

All rights reserved. Unless otherwise specified no part of this publication may be

reproduced or utilized in any form or by any means, electronie or mechanlcal,

including photocopying and microfilm, without Permission in writing from the publisher

ISO/IEC Copyright Office . Case Postale 56 . CH-121 1 Geneve 20 . Switzerland
Printed in Switzerland
---------------------- Page: 2 ----------------------
ISO/IEC 15307: 1997(E)
5 Conventions and notations
5.1 Representation of numbers
5.2 Dimensions
5.3 Names
5.4 Acronyms
6 Environment and safety
6.1 Cartridge and tape testing environment
6.2 Cartridge operating environment
6.3 Cartridge storage environment
6.4 Safety
6.4.1 Safeness
6.4.2 Flammability
6.5 Transportation
Section 2 - Requirements for the unrecorded tape
7 Mechanical and electrical requirements
7.1 Material
7.2 Tape length
7.3 Width
7.4 Total thickness
7.5 Discontinuity
7.6 Longitudinal curvature
7.6.1 Requirement
7.6.2 Procedure
7.7 Out-of-Plane distortions
7.8 Cupping
7.9 Roughness of the coating surfaces
7.9.1 Roughness of the back coating surface
7.9.2 Roughness of the magnetic coating surface
7.10 Coating adhesion
7.11 Layer-to-layer adhesion
7.11.1 Requirements
7.11.2 Procedure
7.12 Modulus of elasticity
7.12.1 Requirement
7.12.2 Procedure
7.13 Flexural rigidity
7.13.1 Requirement
7.13.2 Procedure
7.14 Tensile yield forte
7.14.1 Procedure
7.15 Electrical resistance
7.15.1 Requirement
7.15.2 Procedure
7.16 Inhibitor tape
7.17 Abrasivity
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ISO/IEC 15307: 1997(E)
7.17.1 Requirement
7.17.2 Procedure
7.18 Light transmittance of the tape and the leader
7.19 Coefficient of dynamic friction
7.19.1 Requirements

7.19.2 Procedure for the measurement of the friction between the magnetic surface and the back surface

7.19.3 Procedure for the measurement of the friction between the magnetic surface or the back surface and Calcium

titanate ceramic
8 Magnetit recording characteristics
8.1 Typical Field
8.2 Signal amplitude
8.3 Resolution
8.4 Overwri te
8.4.1 Requirement
8.5 Peak shift
8.5.1 Requirement
8.5.2 Procedure
9 Tape quality
9.1 Missing pulses
9.1.1 Requirement
9.2 Missing pulse zone
9.2.1 Requirement
9.3 Tape durability
Section 3 - Mechanical specifications of the tape cartridge
10 General
10.1 Bottom side and right side
10.2 Back side and left side
10.3 Tape reel
10.4 Tape leader
10.5 Front side
10.6 Operation of the cartridge
10.7 Tape winding
10.8 Moment of inertia
10.9 Material
Section 4 - Requirements for an interchanged tape
11 Method of recording
11.1 Physical recording density
11.2 Channel bit cell length
11.2.1 Average Channel bit cell length
11.2.2 Long-term average Channel bit cell length
11.2.3 Short-term average Channel bit cell length
11.3 Flux transition spacing
11.4 Read Signal amplitude
11.5 Azimuth
11.6 Channel skew
12 Tape format
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OISO/IEC ISO/IEC 15307: 1997(E)
12.1 Reference Edge
12.2 Direction of recording
12.3 Tape layout
12.4 Calibration and Directory Area
12.4.1 Scratch Area
12.4.2 Guard Area G 1
12.4.3 Calibration Tracks Area
12.4.4 Guard Area G2
12.4.5 Directory Area
12.4.6 Guard Area G3
12.5 Data Area
12.5.1 Physical tracks
12.5.2 Width of the physical tracks
12.5.3 Logical tracks
12.5.4 Locations of the physical tracks
12.5.5 Layout of tracks in the Data Area
13 Data format
13.1 Data Bytes
13.2 Logical Blocks
13.3 Data Blocks
13.4 Types of Logical Blocks
13.5 Entities
13.6 Logical Block format
13.6.1 Preamble
13.6.2 Sync
13.6.3 Data Field
13.6.4 EDC
13.6.5 Control Field 1 (CFl)
13.6.6 Control Field 2 (CF2)
13.6.7 CRC
13.6.8 Postamble
14 Use of Logical Blocks
14.1 Data Blocks
14.2 Filler Blocks
14.3 End of Track Blocks (EOTR)
14.4 End of Data Blocks (EOD)
14.5 ECC Blocks
15 Format of Entities
16 Error handling
A - Measurement of light transmittance
B - Generation of the Data Block CRCs
C - ECC generation
D - Generation of page CRCs
E - Format of MAP entries
F - Format of Control Field 1
G - Format of Control Field 2
H - Recommendations for transportation
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ISO/IEC 15307: 1997(E)
J - Inhibitor tape
K - Recommendations on tape durability
L - Handling guidelines
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OISO/IEC ISO/IEC 15307: 1997(E)

ISO (the International Organization for Standardization) and IEC (the International Electrotechnical Commission) form the

specialized System for worldwide standardization. National bodies that are members of ISO or IEC participate in the

development of International Standards through technical committees established by the respective organization to deal with

particular fields of technical activity. ISO and IEC technical committees collaborate in fields of mutual interest. Other

international organizations, governmental and non-governmental, in liaison with ISO and IEC, also take part in the work.

In the field of information technology, ISO and IEC have established a joint technical committee, ISO/IEC JTC 1. Draft

International Standards adopted by the joint technical committee are circulated to national bodies for voting. Publication as an

International Standard requires approval by at least 75% of the national bodies casting a vote.

International Standard ISO/IEC 15307 was prepared by ECMA (as ECMA-23 1) and was adopted, under a special “fast-track

procedure ”, by Joint Technical Committee ISO/IEC JTC 1, Information technology, in parallel with its approval by national

bodies of ISO and IEC.

Annexes A to G form an integral part of this International Standard. Annexes I-I to L are for information only.

---------------------- Page: 7 ----------------------
ISO/IEC 15307: 1997(E) OISO/IEC

This International Standard constitutes a further development of the family of DLT-formatted magnetic tape cartridges. It

allows for a capacity of 20 Gbytes of uncompressed data, or, typically, of 40 Gbytes of compressed user data.

. . .
---------------------- Page: 8 ----------------------
ISO/IEC 15307: 1997 (E)
Information technology - Data interchange on 12,7 mm 12%track magnetic tape
DLT 4 format
cartridges -
Section 1 - General
1 Scope

This International Standard specifies the physical and magnetic characteristics of a 12,7 mm wide, 12%track magnetic tape

cartridge, to enable interchangeability of such cartridges. It also specifies the quality of the recorded Signals, a format - called

Digital Linear Tape 4 (DLT 4) - and a recording method. Together with a labelling Standard, for instance ISO 1001 for

Magnetit Tape Labelling, it allows full data interchange by means of such magnetic tape cartridges.

21 . Magnetit tape cartridges

A magnetic tape cartridge shall be in conformance with this International Standard if it satisfies all mandatory requirements of

this International Standard. The tape requirements shall be satisfied throughout the extent of the tape.

22 . Generating Systems

A System generating a magnetic tape cartridge for interchange shall be entitled to Claim conformance with this International

Standard if all the recordings that it makes on a tape according to 2.1 meet the mandatory requirements of this International

Receiving Systems
23 .

A System receiving a magnetic tape cartridge for interchange shall be entitled to Claim conformance with this International

Standard if it is able to handle any recording made on a tape according to 2.1.
3 Normative references

The following Standards contain provisions which, through reference in this text, constitute provisions of this International

Standard. At the time of publication, the editions indicated were valid. All Standards are subject to revision, and Parties to ag-

reements based on this International Standard are encouraged to investigate the possibility of applying the most recent editions

of the Standards indicated below. Members of IEC and ISO maintain registers of currently valid International Standards.

ISO 1001: 1986, Information processing - File structure and labelling of magnetic tapes for information interchange.

ISO 1302: 1992, Technical drawings - Method of indicating surface texture.
4 Definitions

For the purposes of this International Standard, the following definitions apply.

41 . Average Signal Amplitude

The average peak-to-peak value of the output Signal from the read head at the physical recording density of 2 142 ftpmm

measured over a minimum length of track of 25,4 mm, exclusive of missing pulses.
42 . azimuth

The angular deviation, in minutes of arc, of the mean flux transition line of the recording made on a track from the line normal

to the Reference Edge.
43 . back surface

The surface of the tape opposite the magnetic coating which is used to record data.

44 . Beginning-Of-Tape marker (BOT)

A hole punched on the centreline of the tape towards the end nearest to the leader.

45 . byte
An ordered set of bits acted upon as a unit.
Note - In this International Standard, all bytes are 8-bit bytes.
---------------------- Page: 9 ----------------------
ISO/IEC 15307: 1997 (E) OISO/IEC
46 . cartridge

A case containing a Single supply reel of 12,7 mm wide magnetic tape with a leader attached at the outer end.

47 . Cyclic Redundancy Check (CRC) Character

A 64-bit Character, generated by a mathematical computation, used for error detection.

48 .
Early Warning (EW)

A Signal generated by the drive indicating the approaching end of the recording area.

49 . Error-Detecting Code (EDC)
A mathematical computation yielding check bytes used for error detection.
4.10 End-Of-Tape marker (EOT)

A hole punched on the centreline of the tape towards the end farthest from the leader.

4.11 Entity

A group of ten Logical Blocks treated as a logical unit and recorded on a logical track.

4.12 Error-Correcting Code (ECC)

A mathematical computation yielding check bytes used for the correction of errors detected by the CRC and the EDC.

4.13 flux transition Position

The Point which exhibits the maximum free-space flux density normal to the tape surface.

4.14 flux transition spacing
The distance on the magnetic tape between successive flux transitions.
4.15 Logical Block

The two physical blocks simultaneously written on, or read from, the two physical tracks of a logical track.

4.16 logical track
A pair of physical tracks that are written or read simultaneously.
4.17 magnetic tape

A tape that accepts and retains magnetic Signals intended for input, output, and storage purposes on Computers and associated

4.18 Master Standard Reference Tape

A tape selected as the Standard for reference field, Signal amplitude, resolution, peakshift, and overwrite characteristics.

Note - The Master Standard Reference Tape has been established by the Quantum Corporation.

4.19 Object
A Record or a Tape Mark Block.
4.20 page
A logical division of a physical block.
4.21 physical block
A set of contiguous bytes recorded on a physical track and considered as a unit.
4.22 physical recording density

The number of recorded flux transitions per unit length of track, expressed in flux transitions per millimetre (ftpmm).

4.23 physical track

A longitudinal area on the tape along which a series of magnetic Signals tan be recorded.

4.24 Record
A collection of User Bytes, the number of which is determined by the host.
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@XSO/IEC ISO/IEC 15307: 1997 (E)
4.25 Reference Edge

The bottom edge of the tape when viewing the magnetic coating of the tape with the BOT to the left and the EOT to the right

of the observer.
4.26 Reference Field
The Typical Field of the Master Standard Reference Tape.
4.27 Secondary Standard Reference Tape

A tape the characteristics of which are known and stated in relation to those of the Master Standard Reference Tape.

Secondary Standard Reference Tapes tan be under Reference “SSRT/DLT4” until the year 2005 from Quantum Corporation, 333 South

Note -
Shrewsbury, Mass. 0 1545-4 195, USA.

It is intended that these be used for calibrating tertiary reference tapes for routine calibration.

4.28 Standard Reference Amplitude (SRA)

The Average Signal Amplitude from the Master Standard Reference Tape when it is recorded with the Test Recording Current

at 2 142 ftpmm.
4.29 Standard Reference Current
The current that produces the Reference Field.
4.30 Test Recording Current
The current that is 1,l times the Standard Reference Current.
4.31 Typical Field

In the plot of the Average Signal Amplitude against the recording field at the physical recording density of 2 142 ftpmm, the

minimum field that Causes an Average Signal Amplitude equal to 95 % of the maximum Average Signal Amplitude.

Conventions and notations
51 . Representation of numbers

The following conventions and notations apply in this Standard, unless otherwise stated.

- A measured value is rounded off to the least significant digit of the corresponding specified value. It implies that a

specified value of 1,26 with a positive tolerante +O,Ol, and a negative tolerante -0,02 allows a range of measured values

from 1,235 to 1,275.

- In each block and in each field the bytes shall be arranged with Byte 1, the least significant, first. Within each byte the bits

shall be arranged with Bit 1, the least significant, first and Bit 8, the most significant bit, last. This Order applies to the data,

and to the input and output of the error-detecting and error-correcting Codes, and to the cyclic redundancy characters.

Letters and digits in parentheses represent numbers in hexadecimal notation.
- The setting of bits is denoted by ZERO or ONE.

- Numbers in binary notation and bit Patterns are represented by strings of 0 and 1 shown with the most significant bit to the

52 . Dimensions

Unless otherwise stated, all dimensions in the format figures are in millimetres with a tolerante oft 50 mm.

53 . Names

The names of basic elements, e.g. specific fields, are written with a capital initial letter.

54 . Acronyms
BOT Beginning of Tape
CF1 Control Field 1
CF2 Control Field 2
Cyclic Redundancy Check (Character)
Error-Correcting Code
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ISO/IEC 15307: 1997 (Ic) OISO/IEC
EDC Error-Detecting Code
EOD End of Data
EOT End of Tape
EOTR End of Track
EW Early Warning
FCTl Forward Calibration Track 1
FCT2 Forward Calibration Track 2
RCTl Reverse Calibration Track 1
RCT2 Reverse Calibration Track 2
2,7 RLI Run Length Limited (method)
SRA Standard Reference Amplitude
Environment and safety

Unless otherwise stated, the conditions specified below refer to the ambient conditions in the test or Computer room and not to

those within the tape drive.
61 . Cartridge and tape testing environment.

Unless otherwise stated, tests and measurements made on the cartridge and tape to check the requirements of this International

Standard shall be carried out under the following condi tions:
- temperature: 23 “C Ifr 2 “C
relative humidity: 40 % to 60 %
conditioning before testing: 24 h
62 0 Cartridge operating environment

Cartridges used for data interchange shall be capable of operating under the following conditions:

- temperature: 10 “C to 40 “C
relative humidity: 20 % to 80 %
Note - Localized tape temperatures in excess of 49 “C may Cause tape darnage.

If during storage and./or transportation a cartridge has been exposed to conditions outside the above values, it shall be

conditioned before use by exposure to the operating environment for a time equal to, or greater than, the time away from the

operating environment up to a maximum of 2 h. There shall be no deposit of moisture on or in the cartridge.

63 . Cartridge storage environment
Cartridges shall be stored under the following conditions:
- temperature: 16 “C to 32 “C
relative humidity: 20 % to 80 %
wet bulb temperature: 26 “C max.

Tapes intended for archiving data for one year or more shall be stored under the following conditions:

- temperature: 18 ”Cto26 ”C
relative humidity: 20 % to 60 %

The stray magnetic field at any Point on the tape shall not exceed 4000 A/m. There shall be no deposit of moisture on or in the

64 0
6.4.1 Safeness

The cartridge and its components shall not constitute any safety or health hazard when used in the intended manner, or through

foreseeable misuse in an information processing System.
6.4.2 Flammability

The cartridge and its components shall be made from materials which, if ignited fi-om a flame, and when so ignited do

not continue to bum in a still carbon dioxide atmosphere.
---------------------- Page: 12 ----------------------
ISO/IEC 15307: 1997 (E)
. Transportation

This International Standard does not specify Parameters for the environment in which cartridges should be transported. Annex

H gives some recommendations for transportation.
Section 2 - Requirements for the unrecorded tape
7 Mechanical and electrical requirements
71 . Material

The tape shall consist of a base material (oriented polyethylene terephthalate film or its equivalent) coated on one surface with

a strong yet flexible layer of ferromagnetic material dispersed in a suitable binder. The other surface of the tape shall be coated

with a non-ferromagnetic conductive coating.
72 . Tape length
The length of the tape from the leadersplice to the hub shall be 557 m If: 5 m.
73 . Width
The width of the tape shall be 12,649 mm t 0,010 mm.

The width shall be measured across the tape from edge to edge when the tape is under a tension of less than 0,28 N.

74 . Total thickness
The total thickness of the tape at any Point shall be between 8,3 Pm and 9,3 Fm.
. Discontinuity

There shall be no discontinuities in the tape between the BOT and EOT such as those produced by tape splicing or

76 . Longitudinal curvature

The longitudinal curvature is measured as the departure of the Reference Edge of the tape from a straight line along the

longitudinal dimension of the tape in the plane of the tape surface.
7.6.1 Requirement

Any deviation of the Reference Edge from a straight line shall be continuous and shall not exceed 0,076 mm within any

229 mm length of tape.
7.6.2 Procedure

Measure at a tension of 1,39 N t 0,28 N in a test fixture equipped with two guides spaced at 229 mm. The two guides shall be

Measure the maximum deviation

spring-loaded to Position the Reference Edge of the tape against two edge control surfaces.

of the Reference Edge of the tape from the line drawn between the two control surfaces.

Out-of-Plane distortions
77 .

All visual evidente of out-of-plane distortion shall be removed when the tape is subjected to a uniform tension of 0,6 N. Out-

of-plane distortions are local deformations which Cause portions of the tape to deviate from the plane of the surface of the tape.

Out-of-plane distortions are most readily observed when the tape is lying on a flat surface under no tension.

78 . Cupping

The departure across the width of the tape from a flat surface shall not exceed 2,54 mm.

Cut a 1 ,O m t 0,l m length of tape. Condition it for a minimum of 3 hours in the test environment by hanging it so that both

surfaces are freely exposed to the test environment. From the centre Portion of the conditioned tape tut a test piece of

approximately 25 mm length. Stand the test piece on its end in a cylinder which is at least 25 mm high with an inside diameter

of 13,0 mm t 0,2 mm. With the cylinder standing on an Optical comparator measure the cupping by aligning the edges of the

test piece to the reticle and determining the distance from the aligned edges to the corresponding surface of the test piece at its

79 . Roughness of the coating surfaces
7.9.1 Roughness of the back coating surface

The back coating surface shall have an arithmetic average roughness Ra between 0,003 Fm and 0,018 Fm (ISO 1302:N 2).

This measurement shall be made using a contacting stylus of radius 12,5 Fm with a 20 mg load, and a 254 Fm tut-off range.

---------------------- Page: 13 ----------------------
ISO/IEC 15307:1997 (E)
7.9.2 Roughness of the magnetic coating surface

The magnetic coating surface shall have an arithmetic average roughness Ra between 0,003 pm and 0,008 pm (ISO 1302: N

3). For this measurement, the contacting stylus radius shall be 125 pm with a 20 mg load, and a 254 um tut-off rang-e.

7.10 Coating adhesion

The forte required to peel any part of the coating from the tape base material shall not be less than 0,4 N.


i. Take a test piece of the tape approximately 380 mm long and scribe a line through the recording coating across the width

of the tape 125 mm from one end.

ii. Using a double-sided pressure sensitive tape, attach the full width of the test piece to a smooth metal plate, with the

magnetic coating (recording surface) facing the plate, as shown in figure 1.

iii. Fold the test piece over MO ’, attach the metal plate and the free end of the test piece to the jaws of a universal testing

machine and set the Speed of the jaw Separation to 254 mm per min.

iv. Note the forte at which any part of the coating first separates from the base material. If this is less than 0,2 N, the tape has

failed the test. If the test piece peels away from the double-sided pressure sensitive tape before the forte exceeds 0,2 N, an

alternative type of double-sided pressure sensitive tape shall be used.
v. Repeat i) to iv) for the back coating.
Scribed line
Recording surface
t 125m.m Pressure-sensitive tape
Figure 1 - Measurement of the coating adhesion
7.11 Layer-to-layer adhesion

Layer-to-layer adhesion refers to the tendency of a layer, when held in close proximity to the adjacent layer, to bond itself to

an adjacent layer so that free and smooth Separation of the layers is difficult.
7.11.1 Requirements
There shall be no evidente of delamination or other darnage to the coatings.
7.11.2 Procedure

i. Fasten one end of a 914 mm length of tape, magnetic coating inwards, to a horizontally mounted stainless steel cylinder

with a low cold-flow adhesive material.
ii. The dimensions of the cylinder shall be:
- diameter: 12,7 mm
- length: 102 mm
iii. Attach a mass of 1 000 g to the opposite end of the tape.

iv. Attach, 25,4 mm above the mass, a narrow Strip of double-sided adhesive tape to the magnetic coating.

v. Slowly rotate the cylinder, so that the tape Winds uniformly around it into a compact and even roll. The double-sided tape

secures the end and prevents unwinding when the mass is removed.

Vi. The cylinder with the tape shall then be exposed to the following temperature and humidity cycle:

---------------------- Page: 14 ----------------------
ISO/IEC 15307:1997 (E)
Time Temperature RH
16 h to 18 h
54 “C 85 %
4h 54 “C 10 % or less
lhto2h 21 “C 45 %
vii. Open the end of the roll and remove the double-sided adhesive tape.
viii.Release the tiee end of the tape.
ix. The outer one or two wraps shall spring loose without adhesion.

x. Hold the free end of the tape and allow the cylinder to fall, thereby unwinding the tape.

xi. The tape shall show no coating delamination, except for the 5 1 mm of tape nearest to the cylinder.

Figure 2 - Measurement of layer-to-layer adhesion
7.12 Modulus of elasticity

The modulus of elasticity (Young ’s modulus) is the ratio of stress to strain in the longitudinal direction.

7.12.1 Requirement
The modulus of elasticity shall be between 4 900 N/mm2 and 11 700 N/mm2.
7.12,2 Procedure

Clamp a test piece of tape at least 178 mm in length with an initial 102 mm Separation between the jaws of a universal testing

machine with a nominal crosshead Speed of 5 mm per minute. Calculate the modulus using the chord of the curve between the

forte at 0 % and 1 % elongation.
7.~3 Flexural rigidity

Flexural rigidity is the ability of the tape to resist bending in the longitudinal direction.

7.13.1 Requirement

The flexural rigidity of the tape in the longitudinal direction shall be between 2 x 1 OW7 N . mm and 8 x 10-17 N l mm.

---------------------- Page: 15 ----------------------
ISO/IEC 15307: 1997 (E)
7.13.2 Procedure
Calculate the flexural rigidity D from the following equation:
E x t3
(1 v )
E = modulus of elasticity obtained from 7.12
t = measured thickness of the tape in mm
= Poisson ’s ratio, set to 0,33
7.14 Tensile yield forte

The tensile yield forte required to elongate the test piece by 3 % shall not be less than 9,6 N.

7.14.1 Procedure

Use a static-weighing-constant-rate-of-grip Separation tester capable of indicating the load with an accuracy of 2 %. Clamp a

test piece of tape at least 178 mm long with an initial 102 mm Separation between the jaws. Elongate the test piece at a rate of

5 1 mm per minute until a minimum elongation of 10 % is reached. The forte required to produce an elongation of 3 % is the

tensile yield forte.
7.15 Electrical resistance
7.151 Requirement
The electrical resistance of any Square area of the magnetic coating shall
- be greater than 50 x 106 Q
- not exceed 50 x 1012 Q
The electrical resistance of any Square area of the back coating shall
- not exceed 100 x 106 Q
7.15.2 Procedure

Condition a test piece of tape in the test environment for 24 h. Position the test piece over two 24-carat gold-plated, semi-

circular electrodes having a radius r = 25,4 mm and a finish of at least N4, so that the recording surface is in contact with each

electrode. These electrodes shall be placed parallel to the ground and parallel to each other at a distance d = 12,7 mm between

their centres. Apply a forte F of 1,62 N to each end of the test piece. Apply a d.c. voltage of 100 V $r 10 V across the

electrodes and measure the resulting current flow. From this value, determine the electrical resistance.

Repeat for a total of 5 positions along the test piece and average the 5 resistance readings. For the back coating repeat the

procedure with the back surface in contact with the electrodes.
Figure 3 - Measurement of ePectricaP resistance
---------------------- Page: 16 ----------------------
ISO/IE@ 15307: 1997 (E)

When mounting the test piece, make sure that no conducting paths exist between the electrodes except that through the coating

under test.
Note - Particular attention should be given to keeping the surfaces clean.
7.16 Inhibitor tape

This Standard does not specify Parameters for assessing whether or not a tape is an inhibitor tape. However, annex J gives

further information on inhibitor tapes.
7.17 Abrasivity

Tape abrasivity is the tendency of the magnetic coating to wear the magnetic heads.

7.17.1 Requirement
The depth of the wear Pattern in a ferrite wear bar shall be less than 1,27 um.
7.17.2 Procedure

A test piece 61 m in length shall be passed for 100 Passes (50 cycles) over a rectangular bar of manganese zinc ferrite. The bar

= 5 mm. The tape Speed shall be 2,54 m/s, the
shall be 0,3 mm wide and its top surface shall be rounded off with a radius r.

tension shall be nominally 1,3 N and the wrap angle shall be 12 ”. The wear depth is measured with a profilometer across the

width of the tape path.

Note - Manganese zinc ferrite should be available from Philips Ceramic Division in Saugerties (NY) under Order part number 3H7.

._._._._. _._._._1_._.-.-._.- \c ._._.-
- 0
Figure 4 - Measurement of abrasivity (not to scale)
7.18 Light transmittance of the tape and the leader
The light transmittance of the tape and the l

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