Information technology — Data interchange on 12,7 mm 208-track magnetic tape cartridges — DLT 5 format

This International Standard specifies the physical and magnetic characteristics of a 12,7 mm wide, 208-track magnetic tape cartridge, to enable physical interchangeability of such cartridges between drives. It also specifies the quality of the recorded signals, a format - called Digital Linear Tape 5 (DLT 5) - and a recording method, thereby allowing data interchange between drives. Together with a labelling standard, for instance International Standard ISO 1001 for Magnetic Tape Labelling, it allows full data interchange by means of such magnetic tape cartridges.

Technologies de l'information — Échange de données sur cartouches de bande magnétique de 12,7 mm, 208 pistes — Format DLT 5

General Information

Status
Published
Publication Date
15-Dec-1999
Current Stage
9093 - International Standard confirmed
Start Date
06-Jan-2005
Completion Date
06-Jan-2005
Ref Project

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ISO/IEC 15896:1999 - Information technology -- Data interchange on 12,7 mm 208-track magnetic tape cartridges -- DLT 5 format
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INTERNATIONAL ISO/IEC
STANDARD 15896
First edition
1999-12-15
Information technology — Data
interchange on 12,7 mm 208-track
magnetic tape cartridges — DLT 5 format
Technologies de l'information — Échange de données sur cartouches
de bande magnétique de 12,7 mm, 208 pistes — Format DLT 5
Reference number
ISO/IEC 15896:1999(E)
ISO/IEC 1999
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ISO/IEC 15896:1999(E)
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ii © ISO/IEC 1999 – All rights reserved
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ISO/IEC ISO/IEC 15896:1999 (E)
Contents
Section 1 - General 1
1 Scope 1
2 Conformance 1
2.1 Magnetic tape cartridges 1
2.2 Generating systems 1
2.3 Receiving systems 1
3 Normative references 1
4 Definitions 1
4.1 Average Signal Amplitude 2
4.2 azimuth 2
4.3 back surface 2
4.4 Beginning-Of-Tape marker (BOT) 2
4.5 block 2
4.6 byte 2
4.7 cartridge 2
4.8 Cyclic Redundancy Check (CRC) character 2
4.9 Early Warning (EW) 2
4.10 Error-Detecting Code (EDC) 2
4.11 End-Of-Tape marker (EOT) 2
4.12 Entity 2
4.13 Error-Correcting Code (ECC) 2
4.14 Envelope 2
4.15 Envelope size 2
4.16 flux transition position 2
4.17 flux transition spacing 2
4.18 logical track 2
4.19 magnetic tape 2
4.20 Master Standard Reference Tape 2
4.21 object 2
4.22 page 2
4.23 physical recording density 2
4.24 physical track 2
4.25 Record 2
4.26 Reference Edge 2
4.27 Reference Field 2
4.28 Secondary Standard Reference Tape 2
4.29 Standard Reference Amplitude (SRA) 3
4.30 Standard Reference Current 3
iii
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ISO/IEC 15896:1999 (E) ISO/IEC
4.31 Test Recording Current 3
4.32 Typical Field 3
5 Conventions and notations 3
5.1 Representation of numbers 3
5.2 Dimensions 3
5.3 Names 3
5.4 Acronyms 3
6 Environment and safety 3
6.1 Cartridge and tape testing environment 3
6.2 Cartridge operating environment 4
6.3 Cartridge storage environment 4
6.4 Safety 4
6.4.1 Safeness 4
6.4.2 Flammability 4
6.5 Transportation 4
Section 2 - Requirements for the unrecorded tape 5
7 Mechanical and electrical requirements 5
7.1 Material 5
7.2 Tape length 5
7.3 Width 5
7.4 Total thickness 5
7.5 Discontinuity 5
7.6 Longitudinal curvature 5
7.6.1 Requirement 5
7.6.2 Procedure 5
7.7 Out-of-Plane distortions 5
7.8 Cupping 5
7.9 Roughness of the coating surfaces 5
7.9.1 Roughness of the back coating surface 5
7.9.2 Roughness of the magnetic coating surface 5
7.10 Coating adhesion 6
7.11 Layer-to-layer adhesion 6
7.11.1 Requirements 6
7.11.2 Procedure 6
7.12 Modulus of elasticity 7
7.12.1 Requirement 7
7.12.2 Procedure 7
7.13 Flexural rigidity 7
7.13.1 Requirement 7
7.13.2 Procedure 7
7.14 Tensile yield force 8
7.14.1 Procedure 8
7.15 Electrical resistance 8
7.15.1 Requirement 8
7.15.2 Procedure 8
7.16 Inhibitor tape 9
7.17 Abrasivity 9
7.17.1 Requirement 9
7.17.2 Procedure 9
7.18 Light transmittance of the tape and the leader 9
7.19 Coefficient of dynamic friction 9
7.19.1 Requirements 9

7.19.2 Procedure for the measurement of the friction between the magnetic surface and the back surface 10

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ISO/IEC ISO/IEC 15896:1999 (E)

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

titanate ceramic 10
8 Magnetic recording characteristics 10
8.1 Typical Field 11
8.2 Signal amplitude 11
8.3 Resolution 11
8.4 Overwrite 11
8.4.1 Requirement 11
8.5 Peak shift 11
8.5.1 Requirement 11
8.5.2 Procedure 11
9 Tape quality 12
9.1 Missing pulses 12
9.1.1 Requirement 12
9.2 Missing pulse zone 12
9.2.1 Requirement 12
9.3 Tape durability 12
Section 3 - Mechanical specifications of the tape cartridge 12
10 General 12
10.1 Bottom side and right side 13
10.2 Back side and left side 14
10.3 Tape reel 14
10.4 Tape leader 15
10.5 Front side 16
10.6 Operation of the cartridge 16
10.7 Tape winding 17
10.8 Moment of inertia 17
10.9 Material 18
Section 4 - Requirements for an interchanged tape 27
11 Method of recording 27
11.1 Physical recording density 27
11.2 Channel bit cell length 27
11.2.1 Average Channel bit cell length 27
11.2.2 Long-term average Channel bit cell length 27
11.2.3 Short-term average Channel bit cell length 27
11.3 Flux transition spacing 27
11.4 Read signal amplitude 27
11.5 Azimuth 28
11.6 Channel skew 28
12 Tape format 28
12.1 Reference Edge 28
12.2 Direction of recording 28
12.3 Tape layout 28
12.4 Calibration and Directory Area 28
12.4.1 Scratch Area 29
12.4.2 Guard Area G1 29
12.4.3 Calibration Tracks Area 29
12.4.4 Guard Area G2 30
12.4.5 Directory Area 30
12.4.6 Guard Area G3 30
12.5 Data Area 30
12.5.1 Physical tracks 31
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ISO/IEC 15896:1999 (E) ISO/IEC
12.5.2 Logical tracks 33
13 Data format 34
13.1 Data Bytes 34
13.2 Data Blocks 34
13.3 Types of Blocks 34
13.4 Entities 34
13.5 Envelopes 34
13.6 Block format 34
13.6.1 Preamble 35
13.6.2 Sync 35
13.6.3 Data Field 35
13.6.4 EDC 36
13.6.5 Control Field 1 (CF1) 37
13.6.6 Control Field 2 (CF2) 38
13.6.7 CRC 39
13.6.8 Postamble 39
14 Use of blocks 39
14.1 Data Blocks 39
14.2 Filler Blocks 39
14.3 End of Track Blocks (EOTR) 40
14.4 End of Data Blocks (EOD) 40
14.5 ECC Blocks 40
15 Format of Entities 40
16 Format of Envelopes 40
17 Error handling 40
Annexes
A - Measurement of light transmittance 41
B - Generation of the Data Block CRCs 44
C - ECC generation 45
D - Generation of page CRCs 48
E - Format of MAP entries 49
F - Format of Control Field 1 50
G - Format of Control Field 2 51
H - Recommendations for transportation 52
J - Inhibitor tape 53
K - Recommendations on tape durability 54
L - Handling guidelines 55
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ISO/IEC ISO/IEC 15896:1999 (E)
Foreword

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.

International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 3.

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 castinga vote.

Attention is drawn to the possibility that some of the elements of this International Standard may be the subject of

patent rights. ISO and IEC shall not be held responsible for identifying any or all such patent rights.

International Standard ISO/IEC 15896 was prepared by ECMA — European association for standardizing

information and communication systems (as ECMA-259) 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 toG form a normative part of this International Standard. Annexes H toL are for information only.

vii
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ISO/IEC 15896:1999 (E) ISO/IEC
Introduction

This International Standard constitutes a further development of the magnetic tape cartridge specified in International Standard

ISO/IEC 15307. The number of tracks is raised to 208. As a result a native capacity of 35 Gbytes or, with compressed data, of

typically at least 70 Gbytes is achieved.
viii
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ISO/IEC 15896:1999 (E) ISO/IEC

4.1 Average Signal Amplitude: The average peak-to-peak value of the output signal from the read head at the physical

recording density of 2 254 ftpmm measured over a minimum length of track of 25,4 mm, exclusive of missing pulses.

4.2 azimuth: The angular deviation, in degrees of arc, of the mean flux transition line of the recording made on a track

from the line normal to the Reference Edge.
4.3 back surface:

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

4.4 Beginning-Of-Tape marker (BOT): A hole punched on the centreline of the tape towards the end nearest to the

leader.

4.5 block: A set of contiguous bytes recorded on a physical track and considered as a unit.

4.6 byte: An ordered set of bits acted upon as a unit.
Note - In this International Standard, all bytes are 8-bit bytes.

4.7 cartridge: A case containing a single supply reel of 12,7 mm wide magnetic tape with a leader attached at the outer

end.

4.8 Cyclic Redundancy Check (CRC) character: A 64-bit character, generated by a mathematical computation,

used for error detection.

4.9 Early Warning (EW): A signal generated by the drive indicating the approaching end of the recording area.

4.10 Error-Detecting Code (EDC): A mathematical computation yielding check bytes used for error detection.

4.11 End-Of-Tape marker (EOT): A hole punched on the centreline of the tape towards the end farthest from the

leader.

4.12 Entity: A group of twenty blocks treated as a logical unit and recorded on a logical track, except Filler Blocks ,if any.

4.13 Error-Correcting Code (ECC): A mathematical computation yielding check bytes used for the correction of

errors detected by the CRC and the EDC.
4.14 Envelope: A group of Entities.
4.15 Envelope size:
The number of Entities in an Envelope.

4.16 flux transition position: The point which exhibits the maximum free-space flux density normal to the tape surface.

4.17 flux transition spacing: The distance on the magnetic tape between successive flux transitions.

4.18 logical track: A group of four physical tracks that are written or read simultaneously.

4.19 magnetic tape: A tape that accepts and retains magnetic signals intended for input, output, and storage purposes on

computers and associated equipment.

4.20 Master Standard Reference Tape: A tape selected as the standard for Reference Field, signal amplitude,

resolution, peak shift, and overwrite characteristics.

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

4.21 object: A Record or a page of type Tape Mark.
4.22 page:
A logical division of a block.

4.23 physical recording density: The number of recorded flux transitions per unit length of track, expressed in flux

transitions per millimetre (ftpmm).

4.24 physical track: A longitudinal area on the tape along which a series of magnetic signals can be recorded.

4.25 Record: A collection of User Bytes, the number of which is determined by the host.

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

4.28 Secondary Standard Reference Tape: A tape the characteristics of which are known and stated in relation to

those of the Master Standard Reference Tape.

Note - Secondary Standard Reference Tapes can be ordered under Reference "SSRT/DLT4"from Quantum Corporation, 333 South Street, Shrewsbury, Mass.

01545-4195, USA. It is intended that these be used for calibrating tertiary reference tapes for routine calibration.

In principle, these Secondary Standard Reference Tapes will be available for a period of 10 years from the publication of the first version of this International

Standard. However, this period may be changed to take into account the demand for such Secondary Standard Reference Tapes.

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ISO/IEC ISO/IEC 15896:1999 (E)

4.29 Standard Reference Amplitude (SRA): The Average Signal Amplitude from the Master Standard Reference

Tape when it is recorded with the Test Recording Current at 2 254 ftpmm.
4.30 Standard Reference Current: The current that produces the Reference Field.

4.31 Test Recording Current: The current that is 1,1 times the Standard Reference Current.

4.32 Typical Field: In the plot of the Average Signal Amplitude against the recording field at the physical recording

density of 2 254 ftpmm, the minimum field that causes an Average Signal Amplitude equal to 95 % of the maximum

Average Signal Amplitude.
5 Conventions and notations
5.1 Representation of numbers

The following conventions and notations apply in this International 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 tolerance +0,01, and a negative tolerance -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

left.
5.2 Dimensions

The dimensions in figure 1 to 4 are nominal dimensions. Unless otherwise stated, all dimensions in figures 8 to 23 are in

millimetres with a tolerance of ± 50 mm.
5.3 Names

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

5.4 Acronyms
BOT Beginning of Tape
CF1 Control Field 1
CF2 Control Field 2
CRC Cyclic Redundancy Check (character)
CT1 Calibration Track 1
CT2 Calibration Track 2
ECC Error-Correcting Code
EDC Error-Detecting Code
EOD End of Data
EOT End of Tape
EOTR End of Track
EW Early Warning
RLL Run Length Limited
SRA Standard Reference Amplitude
6 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.
6.1 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 conditions:
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ISO/IEC 15896:1999 (E) ISO/IEC
− temperature: 23 °C ± 2 °C
− relative humidity: 40 % to 60 %
− conditioning before testing: 24 h
6.2 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 %
− wet bulb temperature: 25 °C max.
Note - Localized tape temperatures in excess of 49 °C may cause tape damage.

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 24 h. There shall be no deposit of moisture on or in the cartridge.

6.3 Cartridge storage environment
Cartridges shall be stored under the following conditions:
− temperature: 16 °C to 32 °C
− relative humidity: 20 % to 80 %

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

cartridge.
6.4 Safety
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

any foreseeable misuse in an information processing system.
6.4.2 Flammability

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

not continue to burn in a still carbon dioxide atmosphere.
6.5 Transportation

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

H gives some recommendations for transportation.
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ISO/IEC ISO/IEC 15896:1999 (E)
Section 2 - Requirements for the unrecorded tape
7 Mechanical and electrical requirements
7.1 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.
7.2 Tape length
The length of the tape from the leader splice to the hub shall be 557 m ± 5 m.
7.3 Width
The width of the tape shall be 12,649 mm ± 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.

7.4 Total thickness

The total thickness of the magnetic tape at any point shall be between 8,3 μm and 9,3 μm.

7.5 Discontinuity

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

7.6 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 ± 0,28 N in a test fixture equipped with two guides spaced at 229 mm. The two guides shall be

spring-loaded to position the Reference Edge of the tape against two edge control surfaces. Measure the maximum deviation of

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

7.7 Out-of-Plane distortions

All visual evidence 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.

7.8 Cupping

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

Cut a 1,0 m ± 0,1 m length of tape. Condition it for a minimum of 3 h 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 cut 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

± 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 centre.

7.9 Roughness of the coating surfaces
7.9.1 Roughness of the back coating surface

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

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

7.9.2 Roughness of the magnetic coating surface

The magnetic coating surface shall have an arithmetic average roughness R between 0,003 µm and 0,008 µm (ISO 1302: N 3).

For this measurement, the contacting stylus radius shall be 12,5 µm with a 20 mg load, and a 254 µm cut-off range.

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ISO/IEC 15896:1999 (E) ISO/IEC
7.10 Coating adhesion

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

Procedure

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 180°, adjacent to, and parallel with, the scribed line. 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 force at which any part of the coating first separates from the base material. If this is less than 0,4 N, the tape has

failed the test. If the test piece peels away from the double-sided pressure sensitive tape before the force exceeds 0,4 N, an

alternative type of double-sided pressure sensitive tape shall be used.
v. Repeat i) to iv) for the back coating.
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 evidence of delamination or other damage 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:

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ISO/IEC ISO/IEC 15896:1999 (E)
Time Temperature RH
16 h to 18 h 54 °C 85 %
4 h 54 °C 10 % or less
1 h to 2 h 21 °C 45 %
vii.Open the end of the roll and remove the double-sided adhesive tape.
viii.Release the free 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 51 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
2 2
The modulus of elasticity shall be between 4 900 N/mm and 11 700 N/mm .
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 3 mm per minute. Calculate the modulus using the chord of the curve between the

force at 0 % and 1 % elongation.
7.13 Flexural rigidity

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

7.13.1 Requirement
-7 -7

The flexural rigidity of the tape in the longitudinal direction shall be between 2 x 10 N ⋅ mm and 8 x 10 N ⋅ mm.

7.13.2 Procedure
Calculate the flexural rigidity D from the following equation:
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ISO/IEC 15896:1999 (E) ISO/IEC
Et×
D = ×−()1 υ
where:
E = modulus of elasticity obtained from 7.12
t = measured thickness of the tape in mm
ν = Poisson's ratio, set to 0,33
7.14 Tensile yield force

The tensile yield force 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

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

tensile yield force.
7.15 Electrical resistance
7.15.1 Requirement
The electrical resistance of any square area of the magnetic coating shall
− be greater than 5 x 10 Ω
− not exceed 50 x 10 Ω
The electrical resistance of any square area of the back coating shall
− not exceed 100 x 10 Ω
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 force F of 1,62 N to each end of the test piece. Apply a d.c. voltage of 100 V ± 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.
r r
Figure 3 - Measurement of electrical resistance

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

under test.
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ISO/IEC ISO/IEC 15896:1999 (E)
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 µm.
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

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

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.

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 leader shall be less than 5 % when measured according to the method specified in

annex A.
7.19 Coefficient of dynamic friction

The coefficient of dynamic friction is measured between the surfaces of the tape, and calcium titanate ceramic.

7.19.1 Requirements
Between the magnetic surface and the back surface : greater than 0,15
Between the magnetic surface and other surfaces: 0,05 to 0,35
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ISO/IEC 15896:1999 (E) ISO/IEC
Between the back surface and calcium titanate: 0,05 to 0,20

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

i. Wrap a first piece of tape around a calcium titanate ceramic cylinder (R = 0,05 μm) of diameter 25,4 mm and wrap it with

a total wrap angle of more than 90° with the back surface outwards.

ii. Wrap a second test piece, with the magnetic surface inwards, around the first test piece with a total wrap angle of 90°.

iii. Exert on one end of the outer test piece a force of F = 0,64 N.
iv. Attach the other end to a force gauge mounted on a linear slide.
v. Drive the slide at a speed of 1 mm/s, measure the force F required.
vi. Calculate the coefficient of dynamic friction γ from the equation
F 1
γ=×
ln( )
F π
where π is the value of the wrap angle in radians.

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

titanate ceramic
i. Wrap a piece of tape around a calciu
...

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