M20-52630-1Issue C January 1997

Instron2630-100 Series Clip-On

Extensometers

Operator’s Guide

PROPRIETARY RIGHTS NOTICE

This document and the information that it contains arethe property of Instron Corporation. Rights toduplicate or otherwise copy this document and rightsto disclose the document and the information that itcontains to others and the right to use the informationcontained therein may be acquired only by writtenpermission signed by a duly authorised officer ofInstron Corporation.

© Copyright 1997 Instron Corporation

Amendment Incorporation Record

AMENDMENTNUMBER

BRIEF DESCRIPTION OFCONTENT

NAME OFPERSON

INCORPORATINGAMENDMENT

1Additional informationcovering Phase 2 andPhase 3 extensometers

Siân Oakes

2Wire clip information

amended. Issue raised toC, ECR35152

Siân Oakes

3

4

5

6

7

8

9

10

Preliminary Pages

iii M20-52630-1

Amendment Incorporation Record

AMENDMENTNUMBER

BRIEF DESCRIPTION OFCONTENT

NAME OFPERSON

INCORPORATINGAMENDMENT

11

12

13

14

15

16

17

18

19

20

Preliminary Pages

iv

GENERAL SAFETY PRECAUTIONSMaterials testing systems are potentially

hazardous!

Materials testing involves inherent hazardsfrom high forces, rapid motions and storedenergy. You must be aware of all moving andoperating components which are potentiallyhazardous, particularly the actuator in aservohydraulic testing system or the movingcrosshead in an electromechanical testingsystem.

Always be aware of the possible hazardsinvolved when operating and maintaining thesesystems. You must not operate any materialstesting equipment unless you are thoroughlyfamiliar with its functions and operation.Unfamiliarity with a materials testing systemcan lead to unexpected actuator or crossheadmotion with the consequent risk of injury anddamage.

Carefully read all relevant manuals and observeall WARNINGS and CAUTIONS. The termWARNING is used where a hazard may lead toinjury or death. The term CAUTION is usedwhere a hazard may lead to damage toequipment or to loss of data.

Ensure that the test set-up to be followed andthe actual test to be performed on materials,assemblies or structures constitutes no hazardto operating personnel.

Make full use of all mechanical and electroniclimits features. These are supplied for your

Preliminary Pages

v M20-52630-1

safety to enable you to prevent movement ofthe actuator piston / moving crosshead beyondthe desired regions of operation.

The following pages detail various generalwarnings that you must heed at all times whileusing materials testing equipment. Morespecific warnings and cautions will be found inthe text whenever your attention needs to bedrawn to a potential hazard.

Your best safety precautions are to gain athorough understanding of the equipment byreading your instruction manuals and to alwaysuse good judgement.

WARNING

DISCONNECT THE ELECTRICALPOWER SUPPLY BEFOREREMOVING THE COVERS OFELECTRICAL EQUIPMENT

You must disconnect the equipment from theelectrical power supply before removing anyelectrical safety covers or replacing fuses. Donot reconnect the main power source while thecovers are removed unless you are specificallyinstructed to do so in the manual. Refit coversas soon as possible.

DISCONNECT POWER SUPPLIESBEFORE REMOVING THE COVERSOF ROTATING MACHINERY.

You must disconnect the equipment from allpower supplies before removing any cover

Preliminary Pages

vi

which gives access to rotating machinery, e.g.belts, screws or shafts. Do not reconnect anypower supply while the covers are removedunless you are specifically instructed to do soin the manual. If the equipment needs to beoperated to perform maintenance tasks with thecovers removed, ensure that all loose clothing,long hair, etc. is tied back. Refit covers as soonas possible.

WARNING

SHUT DOWN THE HYDRAULICPOWER SUPPLY AND DISCHARGEHYDRAULIC PRESSURE BEFOREDISCONNECTION OF ANYHYDRAULIC FLUID COUPLING.

Do not disconnect any hydraulic couplingwithout first shutting down the hydraulic powersupply and discharging stored pressure to zero.Tie down or otherwise secure all pressurisedhoses to prevent movement during systemoperation and to prevent the hose fromwhipping about in the event of a rupture.

SHUT OFF THE SUPPLY OFCOMPRESSED GAS ANDDISCHARGE RESIDUAL GASPRESSURE BEFOREDISCONNECTION OF ANYCOMPRESSED GAS COUPLING.

Preliminary Pages

vii M20-52630-1

Do not release gas connections without firstdisconnecting the gas supply and dischargingany residual pressure to zero.

WARNING

USE PROTECTIVE SHIELDS ORSCREENS IF ANY POSSIBILITY OFA HAZARD EXISTS FROM THEFAILURE OF A SPECIMEN,ASSEMBLY OR STRUCTURE UNDERTEST.

Protective shields should be used whenever arisk of injury to operators and observers existsfrom the failure of a test specimen, assembly orstructure, particularly where explosivedisintegration may occur. Due to the widerange of specimen materials, assemblies orstructures that may be tested using materialstesting equipment, any hazard resulting fromthe failure of a test specimen, assembly orstructure is entirely the responsibility of theowner and user of the equipment.

PROTECT ELECTRICAL CABLESFROM DAMAGE ANDINADVERTENT DISCONNECTION.

The sudden loss of controlling and feedbacksignals which can result from a disconnected ordamaged cable causes an open loop conditionwhich may drive the actuator of crossheadrapidly to its extremes of motion. All electricalcables, particularly transducer cables, must be

Preliminary Pages

viii

protected from damage. Never route cablesacross the floor without protection, nor suspendcables overhead under excessive strain. Usepaddings to avoid chafing where cables arerouted around corners or through wall openings.

WARNING

WEAR PROTECTIVE CLOTHINGWHEN HANDLING EQUIPMENT ATEXTREMES OF TEMPERATURE.

Materials testing is often carried out atnon-ambient temperatures using ovens,furnaces or cryogenic chambers. Extremetemperature means an operating temperatureexceeding +60 °C (140 °F) or below 0 °C(32 °F). You must use protective clothing, suchas gloves, when handling equipment at thesetemperatures. A warning notice concerning lowor high temperature operation must bedisplayed whenever temperature controlequipment is in use. You should note that thehazard from extreme temperature can extendbeyond the immediate area of the test.

TAKE CARE WHEN INSTALLING ORREMOVING A SPECIMEN,ASSEMBLY OR STRUCTURE.

Installation or removal of a specimen, assemblyof structure involves working inside the hazardarea between the grips or fixtures. Keep clearof the jaws of a grip or fixture at all times.Keep clear of the hazard area between the gripsor fixtures during actuator or crosshead

Preliminary Pages

ix M20-52630-1

movement. Ensure that all actuator orcrosshead movements necessary for installationor removal are slow and, where possible, at alow force setting.

WARNING

BEFORE THE EXTENSOMETER ISUSED IN STRAIN CONTROL,CHECK THE FOLLOWING:

1. Ensure that the extensometeris securely attached to thespecimen.2. Ensure that the extensometeris calibrated.3. Set the Load, Position andStrain limits.4. Ensure that the testingmachine loop-shapingparameters are set correctly.

BEFORE REMOVING THEEXTENSOMETER FROM THESPECIMEN AT ANY TIME, ENSURETHAT THE MACHINE IS NOT INSTRAIN CONTROL!

Preliminary Pages

x

Preliminary Pages

xi M20-52630-1

Table Of Contents

Chapter Page

INTRODUCTION 1-1

GENERAL 1-1

BASIC FEATURES 1-2

EQUIPMENT SUPPLIED 1-4

OPTIONAL ACCESSORIES & SPARES 1-4

SPECIFICATION 2-1

ENVIRONMENTAL 2-1

OPERATION 3-1

GAUGE LENGTH SETTING 3-1

SPECIMEN ATTACHMENT 3-3

Wire Clip 3-3

Variable Pressure SpecimenClamp 3-5

Elastic Bands or O-Rings 3-7

Fitting to the Specimen usingBoth Hands 3-8

Fitting to the Specimen usingOne Hand 3-9

CABLE CLEAT AND EXTENSOMETERHOLDER 3-10

Preliminary Pages

xi M20-52630-1

KNIFE EDGE CHANGING 3-12

Specimen Centering Stops 3-13

IMPORTANT SAFETY NOTE 3-14

CALIBRATION 3-15

Automatic ElectricalCalibration 3-15

Manual ElectricalCalibration 3-16

Manual MechanicalCalibration 3-18

VERIFICATION 3-19

APPENDIX ACLIP SIZES A-1

CLIPS FOR ROUND SPECIMENS A-2

CLIPS FOR RECTANGULARSPECIMENS A-4

Notes A-6

Preliminary Pages

xii

LIST OF ILLUSTRATIONS

Figure Page1-1. Case Layout 1-5

3-1. Gauge Length Setting with thecone-latch released 3-1

3-2. Gauge Length Setting with thecone-latch engaged(gauge length set) 3-2

3-3. Insertion of Clips 3-4

3-4. Wire clips in use 3-4

3-5. Specimen attachment using theoptional Specimen Clampsand Pivot Knife Edges 3-6

3-6. Specimen attachment usingelastic bands 3-7

3-7. Two-handed Installation 3-8

3-8. Single-handed Installation 3-9

3-9. Extensometer suspended fromcleat post — T-slot machines 3-10

3-10. Extensometer suspended fromcleat post — steel coveredmachines 3-11

3-11. Knife Edge Replacement 3-12

Preliminary Pages

xiii M20-52630-1

3-12. Specimen Stops 3-13

3-13. Extensometer mounted on anoptional calibration fixture(Cat. No. 2602-017) 3-17

List of Tables

Table Page1. Extensometer Gauge Lengths

and Travel 2-1

2. General Specification 2-3

3. Machine Compatibility 2-5

4. Extensometer PhysicalCompatibility with 3119 SeriesTemperature Chambers 2-8

Preliminary Pages

xiv

INTRODUCTION

GENERALThe 2630-100 series extensometers convertthe mechanical displacement of a strainedtest specimen into an electrical signal. Whenused with the current range of Instrontesting machines, each extensometer isautomatically recognised, and is able to becalibrated at the touch of a button.

The displacement is transmitted by a lightrigid frame to strain gauges bonded to aflexural element. The gauges are arranged ina fully active four-arm Wheatstone Bridgecircuit.

The 2630-100 series of extensometersincludes different gauge lengths/strain rangeoptions to suit a wide range of specimencharacteristics.

Robust construction provides accuracy andreliability. As with all measuringinstruments, rough handling, contaminationwith dirt and moisture effect calibration andshorten the life of the instrument.

The extensometer is supplied in afoam-lined presentation case, dimensions350 mm (13.8 in.) long, 260 mm (10.2 in.)wide and 85 mm (3.3 in.) deep. Theshipping weight is 0.9 kg (2 lbs).

When not in use, the extensometer shouldbe stored in the presentation case.

INTRODUCTION

1-1 M20-52630-1

BASIC FEATURES• Ergonomic, lightweight,

cross-braced design with overloadprotection.

• Easy attachment and release fromthe specimen facilitatesingle-handed operation.

• Simple, cone latch gauge-lengthsetting method with automaticdisengagement.

• Precise, fixed gauge-lengths withautomatic recognition andcalibration capability.

• Available in metric and U.S.Customary versions to meetISO 9513 and ASTM E83standards of accuracy.

• Low operating-force arms withsingle-bevel, interchangeable knifeedges.

• Suitable for a wide range ofspecimen materials, geometry andsize with a choice of attachmentmethods.

• Combined cable cleat andextensometer holder withprovision for retaining cordattachment to the extensometer.

• High impact plastic storage casewith a contour moulded insert,securely retains the extensometer

INTRODUCTION

1-2

and accessory parts together withits Calibration Certificate andcomprehensive operating manual.

INTRODUCTION

1-3 M20-52630-1

EQUIPMENT SUPPLIEDRefer to Figure 1-1.

1 Extensometer

2 Cable cleat and extensometer holder

3 Allen key

4 11 pairs of wire clips

5 Specimen centering stops

6 Operator’s guide

7 Calibration certificate

8 Foam lined presentation case

OPTIONAL ACCESSORIES &SPARES

1 Variable pressure specimen clamps: see page 3-5.

2 Replacement knife edges, one pair, straightprofile. All purpose use on round and rectangularcross section specimens. Cat No. 2601-077.

3 Replacement knife edges, one pair. Three pointcontact for flat specimens that are not truly flat.Cat No. 2601-078.

4 Replacement knife edges one pair. Radiused edgefor flat specimens that are not truly flat.Cat No. 2601-079.

5 Digital Readout Extensometer Calibrator for manualspan setting. Cat No. 2602-017.

7 Wire clips (see Appendix A).

8 O-Rings, internal diameter 11 mm unstretched.(Instron Part No. T1351-1034).

INTRODUCTION

1-4

CASE OPERATOR’S GUIDE

ALLENKEY

CLIPS FOR RECTANGULARSPECIMENS

CLIPS FOR ROUNDSPECIMENS

EXTENSOMETERCABLE CLEAT AND

EXTENSOMETER HOLDER

SPECIMENSTOPS

Figure 1-1. Case Layout

INTRODUCTION

1-5 M20-52630-1

SPECIFICATIONTable 1. Extensometer Gauge Lengths and Travel

G.Lmm(in.)

Strain % Travel mm (in.)Cat.No.

*Class ISO 9513 (ASTM E83)Strain %

Overall Dimensionsmm (in.)

OperatingForceg (lbs)

+Weightg (lbs)

CodeType

+ve -ve +ve -ve 2630- Class 0.5 (B-2) Class 1 (C) Length Width Height

8 50 50 4 4 120 0, +50 30, +50 67 (2.64) 39 (1.5) 25 (1) 20 (0.04) 27 (0.06) Dual

(0.3) 50 50 (0.15) (0.15) 121 0, +50 30, +50 67 (2.64) 39 (1.5) 25 (1) 20 (0.04) 27 (0.06) Dual

10 10 10 1 1 101 -10, +10 67 (2.6) 39 (1.5) 25 (1) 160 (0.35) 27 (0.06) Single

10 50 50 5 5 102 0, +50 30, +50 67 (2.64) 39 (1.5) 25 (1) 20 (0.04) 27 (0.06) Single

(0.5) 10 10 (0.05) (0.05) 103 -10, +10 67 (2.64) 39 (1.5) 25 (1) 170 (0.37) 27 (0.06) Single

(0.5) 50 50 (0.25) (0.25) 104 0, +50 30, +50 67 (2.64) 39 (1.5) 25 (1) 20 (0.4) 27 (0.06) Single

25 10 10 2.5 2.5 105 -10, +10 100 (4) 39 (1.5) 52 (2) 55 (0.12) 56 (0.12) Single

25 50 10 12.5 2.5 106 0, +50 115 (4.5) 39 (1.5) 58 (2.3) 75 (0.17) 58 (0.13) Single

25 100 10 25 2.5 107 0, +70 0, +100 132 (5.2) 39 (1.5) 69 (2.7) 45 (0.1) 60 (0.13) Single

(1) 10 10 (0.1) (0.1) 108 -10, +10 100 (4) 39 (1.5) 52 (2) 56 (0.12) 56 (0.12) Single

2-1

SPEC

IFICA

TION

G.L

mm

(in.)

Stra

in%

Tra

velm

m(in

.)C

at.

No

.*C

lass

ISO

9513

(AST

ME8

3)St

rain

%

Ove

rall

Dim

en

sion

sm

m(in

.)O

pe

ratin

gFo

rce

g (

lbs)

+W

eig

ht

g(lb

s)

Co

de

Typ

e

+ve

-ve

+ve

-ve

2630

-C

lass

0.5

(B-2

)C

lass

1(C

)Le

ng

thW

idth

He

igh

t

(1)

5010

(0.5

)(0

.1)

109

0, +

5011

5(4

.5)

39(1

.5)

58(2

.3)

75(0

.17)

58 (

0.13

)Si

ng

le

(1)

100

10(1

)(0

.1)

110

0, +

700,

+10

013

2(5

.2)

39(1

.5)

69(2

.7)

45(0

.1)

60 (

0.13

)Si

ng

le

5010

105

511

1-1

0,+

1010

0(4

)39

(1.5

)72

(2.8

)45

(0.1

)60

(0.

13)

Sin

gle

5050

525

2.5

112

0, +

350,

+50

132

(3.2

)39

(1.5

)72

(2.8

)45

(0.1

)60

(0.

13)

Sin

gle

5010

010

505

113

0, +

700,

+10

018

1(7

.1)

39(1

.5)

72(2

.8)

37(0

.08)

70 (

0.15

)D

ua

l

(2)

1010

(0.2

)(0

.2)

114

-10,

+10

100

(4)

39(1

.5)

72(2

.8)

45(0

.1)

60 (

0.13

)Si

ng

le

(2)

505

(1)

(0.1

)11

50,

+35

0,+

5013

2(5

.2)

39(1

.5)

72(2

.8)

45(0

.1)

60 (

0.13

)Si

ng

le

(2)

100

10(2

)(0

.2)

116

0, +

700,

+10

018

1(7

.1)

39(1

.5)

72(2

.8)

37(0

.08)

70 (

0.15

)D

ua

l

8010

18

0.8

117

0, +

1011

6(4

.6)

39(1

.5)

101

(4)

60(0

.13)

60 (

0.13

)D

ua

l

8050

540

411

80,

+35

0,+

5018

1(7

.1)

39(1

.5)

101

(4)

45(0

.1)

70 (

0.15

)D

ua

l

100

505

505

119

0, +

350,

+50

181

(7.1

)39

(1.5

)12

1(4

.8)

37(0

.08)

70 (

0.15

)D

ua

l

*: +:

Wh

en

ca

libra

ted

usin

ga

pp

rop

riate

ca

libra

tion

ap

pa

ratu

sth

ese

ext

en

som

ete

rsa

reg

uara

n-

tee

dto

me

et

the

sta

ted

cla

ssifi

ca

tion

.Ou

tsid

eth

ese

sta

ted

ran

ge

sth

ee

xte

nso

me

ters

inc

om

pre

ssiv

em

od

eg

en

era

llyp

erf

orm

toIS

O 1

.0o

rAST

MC

cla

ssifi

ca

tion

.W

eig

ht

exc

lud

es

ca

ble

an

dc

on

ne

cto

r.2-2 M20-52630-1

SPECIFICATION

Table 2. General Specification

Creep (3 mins - 5 secs)

Effe

ct

of

Tem

pe

ratu

re o

nse

nsit

ivity

-0.0

06,2

0 to

100

°C(t

ypic

al)

-0.0

08,1

00 t

o15

0°C

(ty

pic

al)

-0.0

1, 1

50to

200

°C(t

ypic

al)

% /

°C

Me

tho

do

fa

tta

ch

me

nt

toSp

ec

ime

n

11ty

pe

so

fwire

clip

s.El

ast

icb

an

ds

(no

tsu

pp

lied

).O

ptio

na

lsp

ec

ime

nc

lam

ps

(re

fert

op

ag

e3-

5).

Imm

ers

ibili

tyN

on

-co

nd

uc

tive

/ n

on

-co

rro

sive

flu

ids,

i.e.

ac

eto

ne

,min

era

lan

dsil

ico

ne

oils

,alc

oh

ol,

etc

.

Ga

ug

e le

ng

th s

ett

ing

Co

ne

latc

h w

itha

uto

ma

tic re

lea

se

Ro

un

d s

pe

cim

en

siz

es

<15

,(0.

6 in

.)a

nd

20

(0.8

in.)

mm

Re

cta

ng

ula

r sp

ec

ime

nsiz

es

Wid

th<

40(1

.6 in

.)Th

ickn

ess

<15

,(0.

6 in

.)m

m

Kn

ifee

dg

eg

ripp

ing

forc

e30

0to

600

(0.6

6 to

1.32

lbs)

, su

bje

ct

toth

e c

orr

ec

tse

lec

tion

of

clip

sg

ram

s

Ma

xim

um

wid

tho

fsp

ec

ime

nw

ith s

pe

cim

en

sto

ps

fitte

d18

mm

(0.

71in

.)

NO

TEFS

—Fu

llSc

ale

.All

valu

es

rela

teto

ate

mp

era

ture

of2

2°C

un

less

oth

erw

isest

ate

d.

2-4 M20-52630-1

SPECIFICATION

Table 3. Machine Compatibility

The extensometer connector plugs contain codes which are used by the testing machine to define gauge length, traveland calibration points. The extensometers are fitted with either a single code or dual codes, as shown in Table 1.

Machine Series AutomaticElectrical CalibrationManual Electrical

Calibration

ManualMechanicalCalibration

Comments

8000 All Not available All

Via user-definedtransducer setupusing first codeonly.

8500 prior to V21 Single code only Single code only Single code only Versions may beidentified via thefront panel orMDC board label.

8500 V21 All except 2630-119,120, 121All except 2630-119,

120, 121All except 2630-119,

120, 121

8500 Plus All All All

2-5

SPEC

IFICA

TION

Ma

ch

ine

Se

ries

Au

tom

atic

Ele

ctr

ica

l Ca

libra

tion

Ma

nu

alE

lec

tric

al

Ca

libra

tion

Ma

nu

al

Me

ch

an

ica

lC

alib

ratio

nC

om

me

nts

6000

All

No

ta

vaila

ble

All

Via

use

r-d

efin

ed

tra

nsd

uc

ers

etu

pu

sing

first

co

de

on

ly.

4500

prio

rto

V2.

25M

S04

Sin

gle

co

de

on

lyA

llA

llV

ers

ion

ma

yb

eid

en

tifie

dvi

ath

eM

ast

erb

oa

rdla

be

l.

4500

po

stV

2.25

MS0

4A

lle

xce

pt

2630

-120

,12

1A

llA

ll

4500

Po

stV

2.25

MS0

5o

rla

ter

All

All

All

4200

/430

0 C

PU

ca

rdw

ith P

RO

Ms

prio

rto

A47

4-71

7,71

8, 7

19, 7

20Si

ng

lec

od

eo

nly

All

All

Ch

ec

kC

PU

ca

rd.

4200

/430

0 C

PU

ca

rdw

ith P

RO

Ms

A47

4-71

7,71

8, 7

19, 7

20

All

exc

ep

t 26

30-1

20,

121

All

All

2-6 M20-52630-1

SPECIFICATION

Ma

ch

ine

Se

ries

Au

tom

atic

Ele

ctr

ica

l Ca

libra

tion

Ma

nu

alE

lec

tric

al

Ca

libra

tion

Ma

nu

al

Me

ch

an

ica

lC

alib

ratio

nC

om

me

nts

4200

/430

0 C

PU

ca

rdw

ithP

RO

MS

A47

4-73

6,73

7,73

8,73

9o

rla

ter

All

All

All

Ch

ec

kC

PU

ca

rd.

2180

/216

0N

ot

ava

ilab

leA

llA

ll

1100

No

All

All

4400

All

exc

ep

t26

30-1

20,1

21A

llA

ll

4400

PR

OM

A47

4-74

0o

rla

ter

All

All

All

5500

Pre

-De

c 9

3A

lle

xce

pt

2630

-120

,12

1A

llA

ll

5500

Po

st-D

ec

93

All

All

All

2-7

SPECIFICATION

ENVIRONMENTALThe extensometer’s simple and easyattachment method make it ideal for usein a temperature chamber.

The extensometer’s temperaturecapability is stated in Table 2.

High relative humidity may altercalibration and it is advisable to confirmthe calibration using a suitablecalibration fixture at the test condition.

CAUTION:

Contamination bycondensation, electricallyconducting fluids, dirt orcorrosive substances maydamage the extensometer.

Table 4.Extensometer Physical Compatibility with

3119 Series Temperature Chambers

ChamberCat. No. Suitable Extensometers

3119-005 All except 2630-113, 116, 118 and 119

3119-006 All except 2630-113, 116, 118 and 119

3119-007 All

3119-008 All

3119-009 All except 2630-113, 116, 118 and 119

SPECIFICATION

2-8 M20-52630-1

OPERATION

GAUGE LENGTH SETTINGBefore strain can be accurately measuredthe extensometer arms must be spaced toset the knife edges at gauge length. Theextensometer features an integral conelatch arm locating system.

To set gauge length press the two roundbuttons with index finger and thumb ofeither left or right hand. Ensure the conelocates in the cone-seat. The extensometerknife edges are now held at the correctgauge length. The extensometer is readyfor attaching to a test specimen (refer toFigures 3-1 and 3-2).

with the cone-latch released

CONE SEAT

CONE PIN

Figure 3-1. Gauge Length Setting

OPERATION

3-1

Verification of gauge length may beconfirmed by engaging the gauge lengthcone latch and checking the distancebetween the knife edges using eithercallipers or a slip gauge.

with the cone-latch engaged(gauge length set)

Figure 3-2. Gauge Length Setting

OPERATION

3-2 M20-52630-1

SPECIMEN ATTACHMENTFor accurate results, effective attachmentof the extensometer to the specimen isessential. Test results may be altered if theknife edges press too firmly into thespecimen. A sign of excessive knife edgepressure is breaking of the specimen at theknife edge point of contact. At the otherextreme, with low knife edge pressure,slippage may occur. This can be identifiedfrom a stress v strain graph by a rapidchange in strain for a small change instress. If a test is to involve strains greaterthan 10%, a higher clamping force may berequired.A number of different attachmentmethods are available offering theflexibility to suit a wide range of testingconditions. Care during attachment shouldavoid any difficulties and permit theoptimum knife edge pressure to beachieved.Knife edges should be replaced if blunt,as described on page 3-12.

Wire ClipClips are available in two profiles toaccommodate round and rectangularspecimens. It is important for good resultsto select the clip that best suits thespecimen. Appendix A gives full sizescale diagrams of the available clips withinformation on the optimum workingrange for each clip. The clips mount intothe extensometer arms from either side,

OPERATION

3-3

using the technique shown in Figure3-3. Figure 3-4 shows the wire clip inoperation holding the extensometer to atypical specimen.

Once the wire clip is selected and a testspecimen is correctly installed in thetesting machine grips the extensometercan be attached.

Figure 3-3. Insertion of Clips

Figure 3-4. Wire clips in use

OPERATION

3-4 M20-52630-1

Variable Pressure Specimen ClampIf preferred, the instrument may bechanged to use variable pressure specimenclamps as supplied on earlier 2630 seriesinstruments. This requires optional notchpivot knife edges to permit the use ofspecimen clamps.

Specimen clamps are an optional extraand can be ordered from Instron using thefollowing Catalogue Numbers:Cat No. 2601-081, specimen clamp andknife edges — Small, minimum gaugelength 10 mm. Accommodates roundspecimens 1 to 9 mm in diameter or flatspecimens to 9 mm wide and 1 to 10 mmthick.Cat No. 2601-082, specimen clamp andknife edges — Medium, minimum gaugelength 25 mm. Accommodates roundspecimens 1 to 15 mm in diameter in di-ameter or flat specimens to 14 mm wideand 1 to 18 mm thick.Cat No. 2601-083,specimen clamp andknife edges — Large, minimum gaugelength 25 mm. Accommodates roundspecimens 1 to 10 mm in diameter or flatspecimens to 25 mm wide and 1 to 10 mmthick.

To fit the Extensometer to the Specimen

Hold the extensometer with the GaugeLength cone-latch engaged and positionthe knife edges against the test specimen.Holding a specimen clamp, straddle the

OPERATION

3-5

specimen above the knife edges of theextensometer. Press the clamp againstthe specimen to compress the springloaded plunger and hook the specimenclamp on the knife edges. Ensure thatthe knife edge seats properly in thespecimen clamp notch pivot. Repeat thesame operation on the lower specimenclamp.When testing round specimens, align the“V” groove of the spring-loaded plungerbefore straddling the specimen.

Note that the notch pivot slots in thespecimen clamp should always pointaway from the gauge length, as shownbelow.

VARIABLE PRESSURESPECIMEN CLAMP

PRESSURE ADJUSTER RING

NOTCH PIVOT

NOTCH PIVOT SLOTSPOINTING OUTWARDS FROM

THE GAUGE LENGTH

Figure 3-5. Specimen attachmentusing the optional Specimen Clamps

and Pivot Knife Edges

OPERATION

3-6 M20-52630-1

Elastic Bands or O-RingsHooks for elastic bands or O-rings are anintegral part of the knife edges, althoughelastic bands and O-rings are not suppliedwith the extensometer. Refer to page 1-4for O-ring details.

Hold the extensometer with the gaugelength cone latch engaged and positionthe knife edges on the test specimen.

Stretch good quality elastic bands orO-rings around the specimen and loop theends over the two knife edge hooks, asshown in Figure 3-6.

Figure 3-6. Specimen attachmentusing elastic bands

OPERATION

3-7

Fitting to the Specimen using BothHands

When testing soft or delicate materials,two-handed installation reduces thepossibility of marking the specimen.

Hold the extensometer with either handand engage the gauge length cone-latch.Using the other hand open the wire clipsto clear the specimen, as shown inFigure 3-7. Position the extensometer inline with the specimen and graduallyrelease the clips. Once the extensometeris attached to the specimen the gaugelength cone-latch can be released. If theextensometer is not held firmly onto thespecimen select a smaller clip.

PRESS TO SETGAUGE LENGTH

CLIP PRONG

Figure 3-7. Two-handed Installation

OPERATION

3-8 M20-52630-1

Fitting to the Specimen using One HandSingle handed installation is useful forworking in temperature cabinets whereaccess is limited.Hold the extensometer with either handand engage the gauge length cone-latch.Hook the wire clip prongs behind thespecimen as shown in Figure 3-8. Pull theextensometer to open the wire clips toclear the specimen. Slide the clip againstthe specimen bringing the extensometer inline with the specimen and graduallyrelease the clips so the knife edges gentlytouch the specimen. Do not slide the knifeedge against the specimen as thespecimen may be marked or the knifeedge blunted. Once the extensometer isattached to the specimen, release thegauge length cone-latch. If theextensometer is not held firmly onto thespecimen select a smaller clip.

PRESS TO SETGAUGE LENGTH

CLIP PRONG

Figure 3-8. Single-handed Installation

OPERATION

3-9

CABLE CLEAT ANDEXTENSOMETER HOLDER

A combined cable cleat andextensometer holder is provided, and isshown in Figures 3-9 and 3-10.

The magnetic base of the cleat can beattached to steel parts of the testingmachine e.g. the column covers. For “T”slot machines with aluminium columncovers the special keeper assembly willslide into the “T” slot and then the cleatwill attach to the keeper.

The slot in the base of the cleat is usedto support the extensometer cable. Thecleat should be positioned to reduce theeffects of cable tension on theextensometer.

KEEPER NUT

SLIDE INTOT-SLOT

Figure 3-9. Extensometer suspendedfrom cleat post — T-slot machines

OPERATION

3-10 M20-52630-1

When the extensometer is not in use but isstill required to be connected to the testingmachine, it may be secured to a cleat postusing the hole provided in theextensometer cover.

Ensure the cleat is returned to thepresentation case, with the magnetattached to the keeper plate when not inuse.

ATTACH TOSTEEL

SURFACE

SLOT FORCABLE

Figure 3-10. Extensometer suspendedfrom cleat post — steel covered

machines

OPERATION

3-11

KNIFE EDGE CHANGINGRefer to Figure 3-11 below. Loosen thesocket head cap screw using thesupplied allen key.

Position replacement knife edge withthe bevel side of the knife edge furthestfrom the cut-out in the extensometerarms. Secure with socket head capscrew ensuring alignment faces of theknife edge and extensometer touch.

SOCKET HEAD CAPSCREW

KNIFE EDGE

BEVELLEDEDGE

ALIGNMENT FACES

Figure 3-11. Knife Edge Replacement

OPERATION

3-12 M20-52630-1

SPECIMEN CENTERING STOPSPrecise alignment of the extensometer isnecessary to ensure the correctmeasurement of strain in a specimen andto enable rapid, precise attachment to thespecimen. To achieve this a pair ofoptional stops are supplied to assist withaligning the extensometer relative to thespecimen. Graduations are marked on thesurface of the stops to allow equal setting.

The installation of a specimen stop isshown below in Figure 3-12.

EXTENSOMETERARM

SPECIMEN STOP

SOCKET HEADCAP SCREW

Figure 3-12. Specimen Stops

OPERATION

3-13

IMPORTANT SAFETY NOTE

WARNING

BEFORE THE EXTENSOMETERIS USED IN STRAINCONTROL, CHECK THEFOLLOWING:

1. Ensure that theextensometer is securelyattached to the specimen.2. Ensure that theextensometer is calibrated.3. Set the Load, Positionand Strain limits.4. Ensure that the testingmachine loop-shapingparameters are setcorrectly.

BEFORE REMOVING THEEXTENSOMETER FROM THESPECIMEN AT ANY TIME,ENSURE THAT THE MACHINEIS NOT IN STRAIN CONTROL.

OPERATION

3-14 M20-52630-1

CALIBRATIONThe extensometer and machineconditioning electronics must becalibrated before use. Three parametersmust be defined: full scale, calibrationpoint and gauge length.

Three methods of calibration are possible:

Automatic Electrical CalibrationThis is the normal method of calibrationfor current Instron testing machines. Theextensometer is self-identifying via itscode resistors. These are interrogated bythe testing machine which has thecalibration parameters stored within itsmemory. If the extensometer is to be usedon an older Instron machine checkcompatibility with automatic calibration,refer to page 2-5.

To operate the automatic electricalcalibration, refer to the operatinginstructions or user’s guide supplied withthe testing machine.

Note: Ensure that theextensometer is set atgauge length, and iscorrectly attached to thetest specimen. Refer topages 3-1 to 3-8.

OPERATION

3-15

Manual Electrical CalibrationThis method can be used if your testingmachine is unable to use theself-identifying feature or if you wish tomodify the calibration parameters.

To operate manual electrical calibrationrefer to the operating instructions oruser’s guide supplied with the testingmachine.

Note: Ensure that the exten-someter is set at gaugelength, and is correctly at-tached to the test speci-men. Refer to pages 3-1to 3-8.

OPERATION

3-16 M20-52630-1

Figure 3-13. Extensometer mounted onan optional calibration fixture

(Cat. No. 2602-017)

OPERATION

3-17

Manual Mechanical CalibrationThis method must be used on oldertesting machines that are unable toperform any other type of calibration. Itis also a way of confirming the electricalcalibration.

A calibration fixture is required formanual mechanical calibration (refer topage 1-4 — Optional Accessories andSpares). The fixture consists of a digitalmicrometer head, mounted on a standframe, with two knurled collets forholding various calibrator spindlescorresponding to types and sizes ofspecimens to be tested. It enables theextensometer to be exercised over itsmechanical displacement range and thespan to be checked or set.

Note: Ensure that the exten-someter is set at gaugelength, and is correctly at-tached to the Calibrator.Refer to pages 3-1 to 3-8.

OPERATION

3-18 M20-52630-1

VERIFICATIONThe achievable ISO or ASTMclassification is given in Table 1 on pages2-1 and 2-2. Certification of the strainmeasurement system which includes theextensometer, conditioning electronicsand readout to the international standardsshould be arranged through accreditedcalibration services. Your local Instronarea office will be able to arrangeverification.

NOTE It is advisable to check theaccuracy of theautomatic/manualelectrical calibration atleast once per year.

OPERATION

3-19

APPENDIX ACLIP SIZES

Use the full-scale diagrams on the followingpages to identify the various clips suppliedwith the extensometer.

CLIP SIZES

Appendix A A-1 M20-52630-1

CLIPS FOR ROUND SPECIMENS(Supplied in pairs)

T1696-1390Ø0 to 3 mm

Ø 0 to 0.12 in.

T1696-1391Ø3 to 6 mm

Ø 0.12 to 0.24 in.

T1696-1392Ø6 to 9 mm

Ø 0.24 to 0.35 in.

CLIP SIZES

Appendix A A-2

T1696-1393Ø9 to 12 mm

Ø0.35 to 0.47 in.

T1696-1394Ø12 to 15 mm

Ø0.47 to 0.59 in.

T1696-1388Ø20 mmØ0.79 in.

CLIP SIZES

Appendix A A-3 M20-52630-1

CLIPS FOR RECTANGULARSPECIMENS

(Supplied in pairs)

T1696-1395SQR 0 to 3 mm

SQR 0 to 0.12 in.

T1696-1396SQR 3 to 6 mm

SQR 0.12 to 0.24 in.

T1696-1397SQR 6 to 9 mm

SQR 0.24 to 0.35 in.

CLIP SIZES

Appendix A A-4

T1696-1398SQR 9 to 12 mm

SQR 0.35 to 0.47 in.

T1696-1399SQR 12 to 15 mm

SQR 0.47 to 0.59 in.

CLIP SIZES

Appendix A A-5 M20-52630-1

NOTESCLIP SIZES

Appendix A A-6